Diagnostic application of immunohistochemistry in pleomorphic sarcomas

Eighteen cases of pleomorphic sarcoma diagnosed or supposed as rhabdomyosarcomas (RMS) and fourteen cases of other soft tissue lesions were stained with five specific antisera (myoglobin, desmin, alpha-1-antitrypsin, Lysozyme, and S-100) by peroxidase antiperoxidase method. The immunohistochemical findings indicated that the majority of the pleomorphic sarcomas (11/18) had to be reclassified as malignant fibrous histiocytoma (MFH), and pleomorphic RMS was indeed rare in adults over the age of 30 years. In this MFH group, desmin was present in all but 3 cases (8/11), supporting that MFH is a tumor originated from mesenchymal cells other than histiocytes. The success of using immunohistochemistry for making pathologic diagnosis depends upon rational application of panels of antibodies. The diagnostic features of pleomorphic sarcomas in routine or special stains are discussed.     

Myogenic regulatory protein expression in adult soft tissue sarcomas. A sensitive and specific marker of skeletal muscle differentiation.

Myogenic regulatory protein (MyoD1) is a DNA-binding nuclear protein that initiates myogenesis in mesenchymal stem cells. Its expression has proved a very sensitive marker of myogenic differentiation in malignant tumors of childhood. In this study, the reliability of MyoD1 expression as marker of skeletal muscle differentiation has been tested in 38 cases of adult-type sarcomas. Frozen sections were stained with the monoclonal antibody 5.8A (MAb 5.8A) developed against recombinant wild-type murine MyoD1. Routinely processed formalin-fixed sections from the same cases were reviewed and immunostained with a panel of antibodies commonly used to detect muscle differentiation: myoglobin, fast-myosin, desmin, muscle-specific actin, alpha-smooth muscle actin. Four cases positively stained with MAb 5.8A: three were high-grade spindle cell sarcomas, the fourth case was an alveolar soft-part sarcoma. Only tumors in which skeletal muscle histogenesis was inferred on the basis of histology and/or immunohistochemistry with conventional muscle markers stained positively for MAb 5.8A. All the other tumors tested, including leiomyosarcomas (11), liposarcomas, (10, including four dedifferentiated liposarcomas), fibrosarcomas (three), malignant fibrous histiocytomas (two), synovial sarcomas (two), and malignant peripheral nerve sheath tumors (two), were negative for MAb 5.8A. The high level of sensitivity and specificity of MyoD1 expression indicates the value of this marker in the diagnosis of soft tissue sarcomas.     

Validity and reproducibility of histologic diagnosis and grading for adult soft-tissue sarcomas

Soft-tissue sarcomas in adults show great variations in histologic type and grade. A valid and reproducible prognostication system is needed to select patients with soft-tissue sarcomas who could benefit from adjuvant chemotherapy. This study was conducted to assess the validity and reproducibility of diagnosis of the histologic type, MIB-1 grade, and mitosis grade, as well as of the 3 components of these grading systems. MIB-1 grade is a recently proposed grading system for predicting the prognosis of patients with adult soft-tissue sarcomas on the basis of 3 criteria (tumor differentiation, necrosis, and MIB-1 score) and replaces the mitotic count in the French system with MIB-1 immunohistochemical staining. Four surgical pathologists from 4 institutions who had experience in diagnostic soft-tissue tumor pathology reviewed 130 cases of soft-tissue sarcoma and independently determined histologic type and grade. The validity of histologic diagnosis was measured by sensitivity and specificity, and that of grading was measured by kappa statistics and percentage agreement with the diagnosis of the expert panel at the National Cancer Center, which was defined as a gold standard. Interobserver reproducibility was measured by kappa and by percentage agreement between the diagnoses of the 4 pathologists. The validity of the diagnosis of histologic type was high for synovial sarcoma, small round-cell sarcoma, and liposarcoma (sensitivity 89% to 100%; specificity, 98% to 100%) but low for malignant fibrous histiocytoma (MFH) and spindle-cell sarcoma (73% to 75%; 93% to 95%). For the grading, the validity of the MIB-1 grade was substantial (kappa = 0.68; agreement, 79%) and higher than that of the mitosis grade (0.54; 69%). The most valid component was tumor differentiation (kappa = 0.79), followed by tumor necrosis (0.66), MIB-1 score (0.59), and mitotic score (0.37). Interobserver reproducibility of histologic diagnosis was high for small round-cell sarcoma, synovial sarcoma, and liposarcoma (kappa = 0.92, 0.90, 0.87; percentage agreement = 99%, 97%, 96%, respectively); for grading, reproducibility was highest for tumor differentiation (0.78; 87%) and second highest for MIB-1 grade (0.68; 79%). We conclude that diagnosis of the type of soft-tissue sarcoma for synovial sarcoma, small round-cell sarcoma, and liposarcoma and the MIB-1 grading system based on tumor differentiation are highly valid and reproducible among Japanese pathologists who are familiar with the grading system, whereas re-evaluation of histologic criteria is essential for other histologic types such as MFH and spindle-cell sarcoma.     

Distinction of endometrial stromal sarcomas from 'hemangiopericytomatous' tumors using a panel of immunohistochemical stains.

Endometrial stromal sarcomas are low-grade malignant tumors that may pose a diagnostic challenge, especially when they are present in an extrauterine site. Owing to the presence of an arborizing vasculature and cells with an undifferentiated appearance, endometrial stromal sarcomas can be confused with several soft-tissue neoplasms. We studied 17 endometrial stromal sarcomas, eight hemangiopericytomas, 14 solitary fibrous tumors, and 16 synovial sarcomas immunohistochemically, detecting the following antigens: CD10, estrogen receptor, progesterone receptor, bcl-2, CD34, smooth muscle antigen, epithelial membrane antigen and cytokeratin (AE1/AE3). Most endometrial stromal sarcomas stained positively for CD10 (16/17), estrogen receptor (17/17), progesterone receptor (15/17), and bcl-2 (17/17). Staining with antismooth muscle antigen was seen in 11 of 17 cases of endometrial stromal sarcoma, with more intense staining seen in areas showing smooth muscle differentiation. Staining with AE1/3 was seen in four of 17 endometrial stromal sarcomas, with two of the positive cases containing epithelioid cells. None of the endometrial stromal sarcomas expressed epithelial membrane antigen or CD34. More than half of the hemangiopericytomas (4/8) and solitary fibrous tumors (9/14) cases demonstrated CD10 expression either focally or in a patchy cytoplasmic and membranous pattern. Hemangiopericytomas, solitary fibrous tumors, and synovial sarcomas did not express estrogen receptor. Four of eight hemangiopericytomas and seven of 14 solitary fibrous tumors also showed patchy progesterone receptor expression. CD34 expression was identified in six of eight hemangiopericytomas and 13 of 14 solitary fibrous tumors, but we did not find expression of CD34 in synovial sarcoma. Differences between endometrial stromal sarcoma and other soft-tissue tumors were detected for all of the immunohistochemical markers (P<0.05), except anti-bcl-2 and AE1/3. Antibodies against CD10 mark a substantial number of hemangiopericytomas and solitary fibrous tumors (albeit not diffusely) and should always be combined with antiestrogen receptor and CD34 when the differential diagnosis includes endometrial stromal sarcoma. Unlike estrogen receptor antibodies, progesterone receptor antibodies show at least focal nuclear staining in most hemangiopericytomas, solitary fibrous tumors and rare synovial sarcomas, and are not useful for this differential diagnosis. All endometrial stromal sarcomas expressed bcl-2, mostly in a diffuse pattern, but this did not distinguish between endometrial stromal sarcoma and mimics. We therefore recommend the use of a small antibody panel comprising anti-CD10, anti-estrogen receptor, and anti-CD34 to distinguish endometrial stromal sarcomas from tumors with a predominant hemangiopericytomatous growth pattern.     

Variable antigen expression in hepatoblastomas.

Hepatoblastoma is a malignant tumor that typically presents as a mass in the liver of a child less than 5 years of age. The diagnosis is usually established by means of a needle core biopsy before the treatment is commenced. The pathologic diagnosis of hepatoblastoma relies on the microscopic identification of typical morphologic features, but these may not be present in a needle core biopsy, and in this setting immunohistochemical staining has an important role in the exclusion of other childhood malignancies. We have studied 12 needle core biopsies from cases of hepatoblastoma, all of which had the diagnosis confirmed by subsequent resection of the tumor, to determine if these tumors show a diagnostic phenotype. The needle biopsies were immunostained with a standard panel of antibodies normally used in the characterization of childhood small round blue cell tumors, with the addition of antibodies directed against alpha-fetoprotein and alpha-1-antitrypsin. Our results indicate that the majority of hepatoblastomas expressed cytokeratins (10/12) and that alpha-1-antitrypsin and alpha-fetoprotein staining were positive in approximately half the cases (5/12 and 7/12, respectively). We also observed frequent expression of antigens normally expressed on other childhood tumors. A significant number of hepatoblastomas (8/12) expressed MIC-2 (CD99) an antigen normally associated with primitive neuroectodermal tumor, 4 cases showed positive staining with the neural-associated antigen NCAM (CD56), and 3 were positive with the neuroblastoma marker NB84. Occasional cases showed expression of the muscle marker desmin (2/12) and 2 cases stained with BCL2. Vimentin expression was seen in 1 case, and a single case also expressed the neural markers PGP9.5 and neurone-specific enolase. In all cases, the tumor cells were negative with CD45, WT1, and S-100. These findings indicate that the primitive cells in hepatoblastoma have a variable immunophenotype and can express antigens normally seen in other childhood malignancies. In the clinical setting of the differential diagnosis of childhood abdominal mass, hepatoblastoma shows no distinct immunohistochemical profile, and the diagnosis requires a combination of the clinical, imaging, and pathologic findings.     

Alpha-1-antitrypsin and lysozyme. Their limited significance in fibrohistiocytic tumors

A wide range of tumors were immunohistochemically analyzed for alpha-1-antitrypsin (AAT) and lysozyme in order to evaluate their specificity as histiocytic markers and their significance in the diagnostic and histogenetic evaluation of fibrohistiocytic tumors. Besides histiocytic lesions, AAT immunoreactivity was commonly found in different types of carcinomas and sarcomas, and strong immunoreactivity was found in carcinoid tumors, malignant melanomas, and schwannomas, which, however, had negative results for lysozyme. The AAT immunoreactivity could be abolished with the absorption of the antibody with purified AAT also in nonhistiocytic tumors. The neoplastic pleomorphic cells in malignant fibrous histiocytomas (MFHs) usually had strongly positive results for AAT, whereas only entrapped histocytes had positive results for lysozyme and for two monoclonal antibodies to histomonocytic cells. The results show that AAT has a relatively low specificity as a histiocytic marker, and one should be careful in concluding the histiocytic nature of tumors, such as MFHs, based on AAT immunostaining. It seems also questionable whether AAT can be used as a diagnostic marker for MFH. The reason for the widespread AAT immunoreactivity in various tumors may be that AAT is taken up from serum to various types of nonhistiocytic tumor cells.     

Caveolin-3 is a sensitive and specific marker for rhabdomyosarcoma.

Caveolin-3 (Cav-3) is a principal structural protein of caveolae membrane domains. Animal studies have revealed that Cav-3 is expressed in skeletal and cardiac myocytes but absent in other types of cells. Recent studies have shown that abnormalities in the Cav-3 gene are associated with some forms of muscular dystrophy, while skeletal muscle abnormalities have been observed in Cav-3 transgenic and knockout mice. In this study the authors evaluated the distribution of Cav-3 in normal human tissues and compared the expression of Cav-3 with that of myogenin and myoD1 in rhabdomyosarcoma (RMS), malignant mixed mullerian tumor (MMMT), and an array of neoplasms that mimic RMS to assess the utility of Cav-3 as a diagnostic marker for tumors with skeletal muscle differentiation. In nonneoplastic human tissues, crisp membrane staining for Cav-3 was present in cardiac and skeletal myocytes and occasionally in arterial smooth muscle cells and prostatic stromal cells, while other cell types were negative for Cav-3. Eighty-eight percent (21/24) of RMS studied were positive for Cav-3. Positive staining was generally observed in the more maturely differentiated tumor cells but not the primitive tumor cells. Eight of nine cases of MMMT stained strongly with Cav-3 in their rhabdomyosarcomatous component but not in other components. Fifty-four other neoplasms (13 leiomyosarcomas, 8 neuroblastomas, 5 lymphomas, 6 Wilms tumors without skeletal muscle differentiation, 5 Ewing sarcomas, 4 malignant fibrous histiocytomas, 4 angiosarcomas, 6 malignant melanomas, and 3 synovial sarcomas) were negative for Cav-3 expression. Nearly all (96% [23/24]) cases of RMS were positive for myogenin, while 88% (21/24) were positive for myoD1. Primitive tumor cells showed significantly increased expression of myoD1 and myogenin; conversely, more differentiated tumor cells were negative or weakly stained. The rhabdomyosarcomatous component of MMMT stained focally with myogenin and myoD1, in contrast to the strong Cav-3 labeling in these cells. These results demonstrate that Cav-3 is specifically expressed in human cardiac and skeletal myocytes. Furthermore, its high specificity and relatively high sensitivity (88%) for tumors with skeletal muscle differentiation suggest that Cav-3 is a valuable marker for these tumors and may be used to assess the degree of differentiation of RMS and to identify residual tumor cells in post-chemotherapy specimens.     

Immunohistochemical staining for apolipoprotein B in human sarcomas

A study of immunocytochemical staining for apolipoprotein B (apo B) in 52 human sarcomas and eight benign soft-tissue tumors is described. A peroxidase-antiperoxidase technique was employed using a rabbit anti-apo B antiserum. All 27 liposarcomas examined were positive for apo B, and 23 of these tumors showed at least 2-plus staining on a scale of 0 to 3 plus. Of the ten myxoid liposarcomas within this group, seven showed 2-plus or 3-plus staining, while the other three stained 1 plus. By contrast, 11 of 13 malignant fibrous histiocytomas were negative for apo B; the remainder showed 1-plus staining. Myxoid areas present in three of these cases were negative for apo B. Five of seven rhabdomyosarcomas stained at least 2 plus for apo B. Both benign and malignant peripheral nerve sheath tumors showed no consistent pattern of staining. We conclude that apo B immunocytochemical staining tends to be high in tumors whose normal tissue counterparts exhibit relatively large numbers of low-density lipoprotein receptors. Furthermore, immunoperoxidase staining for apo B should be a useful adjunct in the evaluation of soft-tissue sarcomas, particularly in cases with myxoid differentiation.     

Malignant fibrous histiocytoma. Evidence of perivascular mesenchymal cell origin immunocytochemical studies with monoclonal anti-MFH antibodies.

Using whole cell antigens prepared from the established lines of human malignant fibrous histiocytoma (MFH), the authors have generated two different monoclonal antibodies (FU3 and FU4) by a mouse hybridoma technique. By indirect immunoperoxidase in frozen tissue sections, FU3 and FU4 revealed strong staining of perivascular mesenchymal cells and fibroblasts. In the spleen FU3 stained perivascular cells of the ellipsoids and the marginal zone of the lymph follicles. Macrophages in granulation tissues as well as monocytes and other blood cells in normal peripheral blood were uniformly negative for the antigen detected by FU3. Among various soft-tissue tumors, MFH and liposarcoma reacted strongly with FU3 and FU4, but synovial sarcoma revealed no reaction with either of the antibodies. Immunoelectron-microscopic studies demonstrated positive reactions with FU3 and FU4 on the surface of MFH cell membrane, which suggests that these antibodies recognized cell surface antigens. In conclusion, MFH shares antigenicity with perivascular mesenchymal cells and fibroblasts as well as liposarcoma. MFH and liposarcoma may have a common origin from the perivascular mesenchymal cells that are supposed to have a potential for multidirectional differentiation.     

A correlative cytologic and histologic study of malignant fibrous histiocytoma: an analysis of 40 cases examined by fine-needle aspiration cytology

A correlative cytologic and histologic study of 40 cases of histologically highly pleomorphic malignant fibrous histiocytoma (MFH) is presented. The fine-needle aspiration biopsy was performed preoperatively, and a diagnosis of malignant soft-tissue tumor could be established in all cases. The cytologic and histologic features corresponded well with each other. The two main cell types were mono- and multinucleated, large polymorphic, often bizarre, histiocyte-like cells and atypical fibroblast-like cells. For a correct diagnosis of pleomorphic MFH, it is important to recognize atypical large polymorphic tumor cells showing signs of phagocytosis: prominent cytoplasmic vacuolization, cell debris or even well-preserved cells within the tumor cell cytoplasm. Phagocytic activity was easily demonstrated in air-dried and May-Grünwald Giemsa-stained material. The differential diagnosis of MFH as opposed to other soft-tissue sarcomas and pleomorphic carcinomas is discussed.     

Cluster analysis of immunohistochemical profiles in synovial sarcoma, malignant peripheral nerve sheath tumor, and Ewing sarcoma.

As a result of overlapping morphologic and immunohistochemical features, it can be difficult to distinguish synovial sarcoma, malignant peripheral nerve sheath tumor, and Ewing sarcoma/primitive neuroectodermal tumor in core biopsies. To analyze and compare immunohistochemical profiles, we stained tissue microarrays of 23 synovial sarcomas, 23 malignant peripheral nerve sheath tumors, and 27 Ewing sarcomas with 22 antibodies potentially useful in the differential diagnosis, and analyzed the data with cluster analysis. Stain intensity was scored as none, weak, or strong. For CD99, tumors with membranous accentuation were independently categorized. Cluster analysis sorted five groups, with like tumors clustering together. Synovial sarcoma clustered into two groups: one cytokeratin and EMA positive (n = 11), the other mostly cytokeratin negative, EMA positive, bcl-2 positive and mostly CD56 positive (n = 9). Malignant peripheral nerve sheath tumor clustered into two groups: one S100 positive, with nestin and NGFR positivity in most (n = 10), the other mostly S100 negative, and variably but mostly weakly positive for nestin and NGFR (n = 11). Ewing sarcomas clustered into a single group driven by membranous CD99 staining. Thirteen cases failed to cluster (outliers), while three Ewing sarcomas clustered into groups of other tumor types. Paired antibodies for each tumor type determined by visual assessment of cluster analysis data and statistical calculations of specificity, sensitivity, and predictive values showed that EMA/CK7 for synovial sarcoma, nestin/S100 for malignant peripheral nerve sheath tumor, and membranous CD99/Fli-1 for Ewing sarcoma yielded high specificity and positive predictive values. Cluster analysis also highlighted aberrant staining reactions and diagnostic pitfalls in these tumors. Hierarchical cluster analysis is an effective method for analyzing high-volume immunohistochemical data.     

Immunohistochemistry of markers of histiomonocytic cells in malignant fibrous histiocytomas. A monoclonal antibody study

Nine cases of malignant fibrous histiocytomas (MFH) were examined immunohistochemically in frozen sections with six different monoclonal antibodies to histiomonocytic and related cells (EBM11, HAM-56, KB90, antibodies to dendritic reticulum cells, HLADR and LCA). Ten other soft tissue sarcomas, two desmoid tumors, twelve carcinomas, three seminomas and four lymphomas were studied for comparison. All cases of MFH showed positivity for histiomonocytic cell antigens. In six cases, the positive cells could be clearly interpreted to be infiltrating non-neoplastic cells. However, immunoreactivity for multiple histiocytic markers (EBM11, HAM-56, KB90, HLADR) was seen in tumor cells in three cases of MFH. In one of these cases, the positivity could be verified with KP1, an antibody to histiomonocytic cells applied in formalin fixed and paraffin embedded tissue. None of the tumors was positive with the antibody to dendritic reticulum cells or LCA. In the series of non-histiocytic tumors, no cases showed widespread positivity for multiple histiocytic markers. Our results suggest that in relation to true histiomonocytic differentiation MFH might be a heterogeneous group of tumors. The widespread immunoreactivity for multiple histiocytic markers in some cases may indicate a true histiomonocytic differentiation in some MFHs.     

Is anti-h-caldesmon useful for distinguishing smooth muscle and myofibroblastic tumors? An immunohistochemical study

Misinterpretation of positive staining of antibodies to desmin, smooth muscle actin, and muscle actin as representing smooth muscle differentiation in the context of a spindle cell tumor is not uncommon. Anti-h-caldesmon is a promising novel immunohistochemical reagent for more specific smooth muscle differentiation. We studied 72 tumors (11 leiomyosarcomas, 26 malignant fibrous histiocytomas [MFHs], 11 fibromatoses, 11 cellular cutaneous fibrous histiocytomas [CCFHs], 5 malignant peripheral nerve sheath tumors, 4 synovial sarcomas, and 4 cases of nodular fasciitis), the reactive myofibroblastic response in 5 cases of acute cholecystitis, and the desmoplastic response surrounding 5 invasive breast carcinomas. Tissues were examined for expression of h-caldesmon, desmin, smooth muscle actin, and muscle actin. Diffuse staining for h-caldesmon was present only within the leiomyosarcomas. Focal staining for h-caldesmon involving less than 1% of lesional cells was present in 3 of 26 MFHs and 1 of 11 CCFHs. There was overlap in staining for the other "myoid" markers in all of the lesions that contained myofibroblasts. Anti-h-caldesmon seems to be a reliable marker of smooth muscle differentiation, and its inclusion in a panel of myoid immunohistochemical reagents should allow distinction of smooth muscle and myofibroblastic tumors.     

Characterization of tumor cells in malignant fibrous histiocytomas and other soft-tissue tumors, in comparison with malignant histiocytes. II. Immunoperoxidase study on cryostat sections.

The authors have investigated a possible relationship between tumor cells of malignant fibrous histiocytomas (MFHs) and histiocytes. This relationship was studied by means of immunophenotyping using monoclonal antibodies specific for the monocyte cell lineage (FMC-17, Mac-1, OKM-1, Leu-M1, and lysozyme) and mono- and polyclonal antibodies specific for fibroblasts (respectively, FIB-86 and FSG). The immunophenotypes of the MFH tumor cells were compared with those of tumor cells of "true" histiocytic tumors. Monocyte lineage-specific determinants could be demonstrated in varying amounts on cells of the "true" histiocytic tumors but not on cells of MFH or other soft-tissue tumors. The reverse was true for determinants on fibroblasts. The absence of these determinants on malignant histiocytes, and their presence on MFH (and also on benign fibrous histiocytomas, fibrosarcomas, schwannomas, osteosarcomas, hemangiosarcomas, leio- and rhabdomyosarcomas) supported the conclusion that MFH tumor cells originate from mesenchymal cells which do not belong to the mononuclear phagocytic system. Subdivision of the MFH tumors revealed that the storiform-pleomorphic subtypes could express HLA-Dr/Ia antigens, like histiocytic tumors. The inflammatory cell subtype, however, lacked these antigens.     

Alpha-inhibin immunoreactivity in soft-tissue neoplasia.

Antibodies directed against alpha-inhibin have been previously reported as staining both sex cord-stromal neoplasms as well as adrenal cortical tumors. This relatively restricted immunoreactivity pattern is useful in the assessment of retroperitoneal masses, especially in a setting of limited tissue (e.g., needle biopsy). However, no study to date has evaluated alpha-inhibin immunoreactivity in soft-tissue neoplasms, which frequently enter the differential diagnosis of retroperitoneal masses. We investigate the incidence of alpha-inhibin staining in a variety of soft-tissue neoplasms by using formalin-fixed, paraffin-embedded tissue sections from 282 previously classified soft-tissue neoplasms with anti-alpha-inhibin (Serotec, 1:75). A modified avidin-biotin complex method was used after heat-induced epitope retrieval. Cytoplasmic granular staining was considered positive. Of the 282 tumors studied, a total of 8 (2.8%) demonstrated positive staining with anti-alpha-inhibin antibody. These included 4 of 25 liposarcomas (16%), 2 of 18 angiosarcomas (11%), 1 of 48 lipomas (2.1%), and 1 of 1 rhabdomyoma (100%). Negative staining was noted among hemangiomas (0/28), schwannomas (0/32), leiomyomas (0/16), fibrosarcomas (0/2), fibromas (0/11), dermatofibromas (0/9), neurofibromas (0/6), synovial sarcomas (0/15), rhabdomyosarcomas (0/10), Triton tumors (0/2), and malignant fibrous histiocytomas (0/59). We conclude that rare soft-tissue tumors, especially those exhibiting either lipomatous or vascular differentiation, demonstrate alpha-inhibin immunoreactivity. These findings re-emphasize the need for a well-construed antibody panel when immunohistochemical methods are employed in the evaluation of retroperitoneal neoplasms. However, the rarity of alpha-inhibin expression by soft-tissue neoplasms provides further support for its overall specificity as a marker of adrenal cortical differentiation in the biopsy evaluation of a retroperitoneal mass.     

Immunohistochemical investigations of tumors of supposed fibroblastic-histiocytic origin

The aim of this study was to localize alpha 1-antitrypsin, ferritin, and lysozyme by means of the indirect immunoperoxidase technique and to evaluate the significance of these antigens as markers of histiocytic differentiation in tumors of a supposed dual fibroblastic-histiocytic origin. The series comprised 31 malignant fibrous histiocytomas (MFH) of the pleomorphic, spindle cell, and myxoid types, four cutaneous fibrous histiocytomas, and four atypical fibroxanthomas, four dermatofibrosarcoma protuberans, and two osteoclastomas of bone. For comparison, 15 soft tissue sarcomas of various other types were examined. Of the MFHs of the pleomorphic type, 18 of 22 (82 per cent) were positively stained for alpha 1-antitrypsin and 12 of 22 (54 per cent) were positively stained for ferritin. Of the five MFHs of the spindle cell type, none was positively stained for alpha 1-antitrypsin, three were positive for ferritin, and one was positive for lysozyme. None of the myxoid variants (corresponding to grade I-II myxofibrosarcoma) was positively stained for either of the antigens. These results and the observations made on the cutaneous fibrous histiocytomas, atypical fibroxanthomas, dermatofibrosarcoma protuberans, and the various soft tissue sarcomas indicated that 1) alpha 1-antitrypsin is a valuable marker of histiocytic differentiation in both benign and malignant fibrous histiocytomas, 2) ferritin can be visualized in more than half of these fibroblastic-histiocytic tumors, and the presence of ferritin distinguishes the spindle cells of these tumors from fibroblasts of connective tissue and most fibrosarcomas, and 3) lysozyme, although a good marker of histiocytic differentiation in ordinary histiocytes and benign fibrous histiocytomas, is a poor marker of neoplastic histiocytes of malignant tumors. The results further support the concept that MFH is a tumor of a dual fibroblastic-histiocytic origin.     

Imatinib mesylate (gleevec)--targeted kinases are expressed in uterine sarcomas.

The purpose of this study was to determine whether 3 tyrosine kinases known to be inhibited by imatinib mesylate are expressed in a variety of uterine sarcomas. The authors assessed c-kit, abl, and platelet-derived growth factor receptor-beta (PDGFR-beta) expression in 8 endometrial stromal sarcomas (ESSs), 5 leiomyosarcomas (LMSs), 4 high-grade endometrial sarcomas (HGESs), and 21 malignant mixed mullerian tumors (MMMTs). Tissue sections were stained with commercially available antibodies for c-kit, abl, and PDGFR-beta. Staining intensity was described as 0 (no staining), +1 (weak), +2 (moderate), and +3 (strong). Positive staining was defined as moderate to strong if found in more than 10% of tumor cells. Expression of c-kit ranged from 0% in LMSs to 25% in HGESs. Protein expression of abl was more significant, ranging from 25% in LMSs and ESSs to 43% in MMMTs. Only 1 LMS sample stained focally for abl (+1). Abl expression was observed in only the carcinomatous elements of the MMMTs, with diffuse staining in the cytoplasm and nucleus. In most, the staining intensity was +2. All tumors stained positive for PDGFR-beta. MMMT samples showed PDGFR-beta expression in both the carcinomatous and sarcomatous portions. In all samples, staining for PDGFR-beta was concentrated at the cell membrane and diffusely in the cytoplasm. These results indicate that many uterine sarcomas express 1 or more of the kinases targeted by imatinib mesylate and that further investigation of imatinib as a therapy for uterine sarcomas is warranted.     

Imprint cytological features of soft tissue sarcomas]

The imprint cytologic features in typical sarcomas, such as malignant fibrous histiocytoma (MFH), fibrosarcoma, malignant peripheral nerve sheath tumor (MPST), liposarcoma, synovial sarcoma, clear cell sarcoma and epithelioid sarcoma, were presented in comparison with each histologic feature. Cytological diagnosis of soft tissue sarcomas is usually difficult because of their rarity, various kinds, wide range of features in the tumor and similar features to those of other tumors. Based on the cellular morphology, sarcoma cells were divided into five cell types as follows: small cell type, spindle cell type, epithelioid cell type, epithelioid-spindle type, and pleomorphic type. The results obtained from "retrospective" immunostainings for decolorized Papanicolau's stained sections with a panel of markers, together with differentiation of the cell type, were useful for the cytological diagnosis of the tumors examined. Since the value of aspiration cytology is much higher than that of imprint cytology in the cytopathologic diagnosis, methods, such as immunostaining and differentiation of the cell type, are recommended in aspiration cytology to make a definitive cytological diagnosis in sarcoma cases.     

The significance of double phenotypic patterns and markers in human sarcomas. A new model of mesenchymal differentiation.

Six soft-tissue sarcomas with two separate and juxtaposed histologic patterns were selected for immunohistochemical analysis. The first pattern was represented by five phenotypes (schwannian-skeletal muscle [Triton], cartilagenous, synovial, adipocytic, and smooth muscle). In each case the second histologic pattern resembled the fibrohistiocytic phenotype, ie, malignant fibrous histiocytoma (MFH). No other histologic patterns were identified. Appropriate cell markers were demonstrated in each of the first patterns; these were not detected in the second patterns. In contrast, the second pattern in all cases expressed alpha 1-antichymotrypsin, a marker commonly found in fibrohistiocytic lesions; this was not identified in any of the first patterns. This loss of one cell-specific marker and gain of another is termed the "antigenic shift" phenomenon and appeared to foretell the emergence of a true second phenotype (the same in each of these cases, which could be termed "dedifferentiated" sarcomas). Therefore, it is hypothesized that MFH is a final common pathway for some types of sarcomas and is the result of tumor progression or "dedifferentiation." The practical implications of this hypothesis concern the approach to sarcoma differential diagnosis and the meaning of an MFH pattern in both metastatic and primary sites. On a theoretic level, this hypothesis and the antigenic shift phenomenon force a reconsideration of the pathways of soft-tissue differentiation. A new model of mesenchymal differentiation incorporating these concepts is described and supported. It provides an explanation for a number of facts in soft-tissue pathology, and its predictions can be tested.     

An immunocytochemical study of T-cell lymphomas using monoclonal and polyclonal antibodies effective in routinely fixed wax embedded tissues

Formalin fixed and paraffin wax embedded tissue from 24 cases of T-cell lymphoma diagnosed using immunocytochemistry on cryostat sections was examined using a panel of eight monoclonal and three polyclonal antisera. The monoclonal antibodies UCHL1 and MT1 proved to be comparable and reliable markers of neoplastic cells in T-cell lymphomas. The B-cell specific marker, MB1, strongly stained all cells in two cases of pleomorphic large cell T-cell lymphoma, large cells in two cases of pleomorphic mixed medium and large cell lymphoma, and isolated clusters of blast cells in four cases of T-zone and angioimmunoblastic lymphadenopathy-like T-cell lymphoma. The cells stained by MB1 expressed T suppressor/cytotoxic surface markers on frozen section. Epithelial membrane antigen, as detected by a polyclonal anti-EMA and the monoclonal antibody HMFG2, was expressed in 36% of tumours especially those of monomorphic large cell and pleomorphic large cell phenotype. Single granules or finely dispersed cytoplasmic granularity was seen in four tumours using the anti-granulocyte reagent Leu M1. Tumour cells in one case stained in a pattern identical to Reed-Sternberg cells in Hodgkin's disease. Granular alpha-1-antitrypsin staining was found in 10 cases of pleomorphic large cell and monomorphic large cell lymphoma. No staining was observed using anti-lysozyme or the monoclonal macrophage specific marker Mac411. Monomorphic and pleomorphic large cell lymphomas tended to show a common immunophenotype with the majority of cells co-expressing alpha-1-antitrypsin HLA-DR and epithelial membrane antigen. Scattered large transformed blast cells in cases of angioimmunoblastic lymphadenopathy-like T-cell lymphomas and T-zone lymphomas shared a similar immunophenotype with the large cell lymphomas. Using a panel of monoclonal antibodies effective in paraffin embedded tissue, diagnostically useful staining profiles which correlate with the morphological phenotype can be established in T-cell lymphomas.