Clear cell sarcoma of tendons and aponeuroses (malignant melanoma of soft parts) in the duodenum: the first visceral case

An ulcerated tumour was removed by a Whipple's operation from the descending part of the duodenum of a 38-year-old male. The tumour cells were mainly spindle-shaped, arranged in nests and had very prominent nucleoli. A few cells contained melanin and melanosomes. Immunoreactivity for S-100 protein and focally for HMB-45 was observed. These features are diagnostic for clear cell sarcoma of tendons and aponeuroses. Because no other primary tumour could be found and the search for similar cases from the literature was unsuccessful, we believe that this tumour is the first reported clear cell sarcoma in a visceral location.     

Hepatic angiomyolipoma with striated granules and positivity with melanoma--specific antibody (HMB-45): a report of two cases.

Angiomyolipoma occurs rarely in the liver, with only 25 previous cases being reported in the English literature. The article describes two additional cases, one of which was multicentric, with results of ultrastructural and immunocytochemical studies. Many of the tumor cells contained numerous electron-dense granules, some with transverse striations like those found in melanosomes. Both tumors stained positively for S-100 protein and melanoma-specific antibody HMB-45. One case also expressed vimentin and neuron-specific enolase. Both were negative for cytokeratin, carcinoembryonic antigen, alpha-fetoprotein, desmin, muscle-specific actin, factor VIII antigen, and chromogranin. Comparison of our ultrastructural findings with those of classic renal angiomyolipoma raises the possibility that the melanosomelike structures may represent renin granules rather than melanosomes, although the latter are not excluded. Expression of HMB-45 in angiomyolipoma has important biologic and diagnostic implications, whether or not it reflects melanocytic differentiation.     

Melanocyte colonization of adenocarcinoma arising in an ovarian dermoid

An adenocarcinoma which arose in a dermoid cyst of the ovary displayed areas of melanocyte colonization and pigmentation. Ultrastructural study revealed the presence of epithelial tumour cells and melanocytes; many tumour cells contained compound melanosomes, but not premelanosomes, suggesting transfer of melanin from melanocytes to tumour cells. Melanocyte colonization of malignant tumours is a curious phenomenon the significance of which remains to be elucidated.     

The presence of stage II melanosomes (premelanosomes) in neoplasms other than melanomas

Aside from melanomas, other nonmelanocytic pigmented tumors synthesize melanin or contain benign passenger melanocytes. While Stage IV melanosomes (mature melanosomes) occur in neoplasms which synthesize melanin as well as in those with benign companion melanocytes, Stage II melanosomes (premelanosomes), which are found in melanocytes and cells of pigmented nonmelanocytic tumors of neural crest origin, are considered the morphologic hallmark of in vivo melanin synthesis. To test this widely held concept, we studied the ultrastructure of representative malignant melanomas and other pigmented tumors (pigmented variants of the nevocellular nevus, squamous cell carcinoma, schwannoma, basal cell carcinoma, and seborrheic keratosis). Discrete intracytoplasmic Stage II melanosomes were noted in neoplastic cells of tumors of neural crest origin (melanoma, schwannoma, and nevocellular nevus), which are widely believed to synthesize melanin. In addition, they were also detected in neoplastic epithelial cells of a squamous cell carcinoma, basal cell carcinoma, and seborrheic keratosis. In these epithelial tumors, a spectrum of melanosomes from Stage II through Stage IV were presumably acquired from nonneoplastic companion melanocytes, which were an integral part of the tumor. Because squamous epithelium has not been shown to synthesize melanin, this study suggests that the finding of intracytoplasmic Stage II melanosomes does not necessarily imply melanin synthesis. When accompanied by melanocytes, epithelial and perhaps other tumors may contain ingested Stage II melanosomes.     

Hepatic Angiomyolipoma with Striated Granules and Positivity with Melanoma-Specific Antibody (HMB-45): A Report of Two Cases

Angiomyolipoma occurs rarely in the liver, with only 25 previous cases being reported in the English literature. The article describes two additional cases, one of which was multicentric, with results of ultrastructural and immunocytochemical studies. Many of the tumor cells contained numerous electron-dense granules, some with transverse striations like those found in melanosomes. Both tumors stained positively for S-100 protein and melanoma-specific antibody HMB-45. One case also expressed vimentin and neuron-specific eno-lase. Both were negative for cytokeratin, carci-noembryonic antigen, a-fetoprotein, desmin, muscle-specific actin, factor VIII antigen, and chromogranin. Comparison of our ultrastructural findings with those of classic renal angiomyolipoma raises the possibility that the melanosomelike structures may represent renin granules rather than melanosomes, although the latter are not excluded. Expression of HMB-45 in angiomyolipoma has important biologic and diagnostic implications, whether or not it reflects melanocytic differentiation.     

Intriguing Case: Pigmented Melanocytie Schwannoma of the Uterine Cervix

A 47-year-old woman had a lesion of the uterine cervix that presented clinically as a protruding or aborted leiomyoma. Grossly the tumor occupied a substantial portion of the cervical and endocervical region. Histologically it showed a spindle cell neoplasm arranged in large fascicles that penetrated deeply into the fibromuscular wall of the cervix. The tumor cells had abundant pink cytoplasm that contained considerable brown melanin granules confirmed by Fontana's stain. Cytologically nuclear pleomorphism, hyperchromatism, and giant nuclear forms were observed. Mitoses were also seen. Localized nuclear palisading was present. Electron microscopic examination of paraffin-embedded material revealed numerous premelanosomes and opaque granules that were compatible with mature melanosomes, thus confirming melanogenesis in the tumor. Tumor cells exhibited focal projections, and the connective tissue showed abnormal spacing of collagen. Basal lamina material was noted focally on tumor cell surfaces. Immunocyto-chemistry showed a positive reaction to S-100 protein and HMB-45 in tumor cell cytoplasm.     

A primary amelanotic melanoma of the vagina, diagnosed by immunohistochemical staining with HMB-45, which recurred as a pigmented melanoma

Usually, malignant melanoma is readily diagnosed by the presence of melanin granules. Although amelanotic melanoma contains a few melanin granules, it is often difficult to differentiate from non-epithelial malignant tumours. This report describes a case of amelanotic melanoma of the vagina, which was originally suspected to be a non-epithelial malignant tumour, but was subsequently correctly diagnosed by immunohistochemical staining with the HMB-45 antibody and for the S-100 protein. A light grey tumour with superficial ulceration was located in the upper third of the vagina. The patient was treated with irradiation followed by chemotherapy. Subsequently, the tumour disappeared and cytology was negative; thus, she achieved complete remission. However, 20 months after complete remission, the tumour recurred locally: the site had a grossly black appearance, which was pathognomonic for a malignant melanoma. Thus, HMB-45 and S-100 protein immunohistochemistry confirmed the diagnosis of amelanotic melanoma.     

Renal angiomyolipoma: further immunophenotypic characterization of an expanding morphologic spectrum

BACKGROUND: Renal angiomyolipoma is a benign tumor histologically characterized by proliferation of spindle cells, epithelioid cells, and adipocytic cells in concert with many thick-walled blood vessels. To add further diagnostic confusion, an epithelioid cell-predominant variant of renal angiomyolipoma has recently been described. HMB-45 immunoreactivity correlates with ultrastructural striated organelles that closely resemble premelanosomes, although no evidence of melanogenesis has been documented in this tumor. OBJECTIVE: To further characterize the immunophenotypic and ultrastructural profile of renal angiomyolipoma based on phenotypic cell type (epithelioid, spindle, and adipocytic cell). DESIGN: Formalin-fixed, paraffin-embedded tissues from 27 renal angiomyolipomas and 8 renal cell carcinomas were immunostained with monoclonal antibodies to the melanoma-associated antigens HMB-45, HMB-50, NKI/C3 (CD63), and tyrosinase; the smooth muscle-related antigens calponin and muscle-specific actin (HHF-35); S100; and cytokeratin (CK). All renal angiomyolipomas were also immunostained with a polyclonal antibody to renin. Ultrastructural examination was performed on 9 selected cases. RESULTS: All renal angiomyolipomas stained positive for HMB-45, HMB-50, NKI/C3, muscle-specific actin (HHF-35), and calponin. Overall, HMB-45, HMB-50, and NKI/C3 preferentially stained the epithelioid cells. Tyrosinase staining was present in 50% of the renal angiomyolipomas with adequate tissue for staining (12 of 24 cases); positive staining and intensity paralleled HMB-45, HMB-50, and NKI/C3. Muscle-specific actin (HHF-35) and calponin preferentially stained the spindle cells. The adipocytic cells stained positive for both melanoma-associated antigens and smooth muscle antigens. Epithelioid cells, spindle cells, and adipocytic cells were CK, S100, and renin negative. Ultrastructural findings paralleled immunohistochemical staining patterns. Premelanosome-like organelles and electron dense granules were more readily detected in the epithelioid cells within the tumor, whereas ultrastructural characteristics of smooth muscle cells were more easily found in the spindle cells. All renal cell carcinomas stained positive for CK, NKI/C3 staining was variable, and all were negative for HMB-45, HMB-50, smooth muscle actin (HHF-35), and calponin. CONCLUSION: In renal angiomyolipoma, the epithelioid and spindle cells have preferential staining patterns for melanoma-associated antigens versus smooth muscle antigens, respectively. Positivity in renal angiomyolipoma for HMB-50, NKI/C3, and tyrosinase, in addition to HMB-45, provides evidence for the presence of different melanoma-associated gene products. Immunophenotypic overlap of the 3 histologically distinct renal angiomyolipoma cell populations suggests a common cell line, supporting a unitarian concept for renal angiomyolipoma. Ultrastructural characteristics of the 3 renal angiomyolipoma cell phenotypes parallel the immunophenotype, giving further support to a common cell line. Our study lends further credence to the perivascular epithelioid cell concept as proposed by Bonetti and colleagues.     

Atypical pleomorphic epithelioid angiomyolipoma localized to the pelvis: a case report and review of the literature

AIMS: Angiomyolipoma is the most common mesenchymal tumour of the kidney. It has been reported in several other sites outside the kidney, mainly in the liver. We report the first case of atypical pleomorphic angiomyolipoma in a man, arising from the pouch of Douglas and extending to the entire abdominal cavity. METHODS: A 17-year-old man underwent a complete resection of a giant abdominopelvic mass. The tissue was formalin fixed and paraffin embedded and 4 micro m thick histological sections were stained with haematoxylin-eosin. Immunohistochemical stains for HMB-45, smooth muscle actin, vimentin, calponin, S100 and desmin were performed. Sections for electron microscopy were also prepared. RESULTS: Microscopic examination revealed a neoplasm composed of pleomorphic epithelioid cells with atypical features, immunoreactive for HMB-45, MART-1, actin, vimentin and calponin, while S100 protein and desmin stains were negative. Ultrastructurally, the tumour cells showed prominent nucleoli, vacuolated cytoplasm, and some premelanosomes. A diagnosis of atypical pleomorphic epithelioid angiomyolipoma was then made. CONCLUSIONS: To date five patients with abdominal epithelioid angiomyolipoma have been described in the literature. All were women. Three of the five patients reported developed metastasis, while our patient is still free of disease at 16 months of follow-up. Clear prognostic pathological features have not been identified.     

Melanin-forming Schwann cells in some oral mucosal lesions

Normal oral mucosa and some mucosal lesions show melanin pigmentation, and it is usually assumed that melanin-containing cells in the lamina propria are melanophages. In a study of oral mucosa from two cases of lichen planus and tow of sublingual keratosis, many brown, intracellular, Masson-Fontana-positive granules were seen. At the ultrastructural level some of the melanin-containing cells displayed characteristics of Schwann cells rather than melanophages. These cells were surrounded by a basal lamina and contained unmyelinated axons. Although the majority of the melanin granules in these cells were compound melanosomes, single melanosomes and premelanosomes were also seen. These findings show that in sublingual keratosis and oral lichen planus lesions some of the melanin-containing cells in the connective tissue may be melanin-forming Schwann cells.     

Balloon cell metastatic melanoma: an important differential in the diagnosis of clear cell tumours

Two cases of metastatic balloon cell melanoma are reported. Each tumour was composed of large clear cells which did not contain melanin, glycogen or fat, but showed positive staining for S-100 protein, NK/1-C3 and HMB-45. In each case the primary lesion was a cutaneous melanoma of typical morphology. It is essential to consider balloon cell melanoma in the differential diagnosis of clear cell tumours. These cases emphasize the need for an accurate clinical history.     

Monotypic epithelioid angiomyolipoma of the liver

AIMS: Monotypic epithelioid angiomyolipoma is a recently recognized renal tumour, which is composed purely of epithelioid cells coexpressing markers of both smooth muscle differentiation and melanogenesis (HMB45). We report here the first case of monotypic epithelioid angiomyolipoma arising in the liver. CASE DETAILS: A 30-year-old woman without tuberous sclerosis complex (TSC) was incidentally found to have a hepatic mass by ultrasonography. Grossly, the resected tumour showed a nodule-in-nodule appearance, with large areas of haemorrhagic necrosis. Microscopically, the tumour was composed of pleomorphic epithelioid cells with clear, eosinophilic cytoplasm. Neither adipocytes nor abnormal vessels were recognized in the tumour. Immunohistochemically, the tumour cells were strongly positive for HMB45 and S100 protein, focally positive for desmin, vimentin and smooth muscle actin, and negative for epithelial markers (cytokeratins, EMA). Ultrastructural analysis showed numerous dense granules with some striated ones resembling melanosomes, myofilaments and pinocytic vesicles in the cytoplasm. Molecular analysis showed no allelic loss of the TSC2 region or 12 other chromosomal regions. The patient is free of disease over 1 year after the operation. CONCLUSION: We consider that this hepatic tumour is closely related to angiomyolipoma, and a counterpart of renal monotypic epithelioid angiomyolipoma.     

C-Kit-positive metastatic malignant pigmented clear-cell epithelioid tumor arising from the kidney in a child without tuberous sclerosis

We report the first pediatric case of malignant pigmented epithelioid clear-cell tumor arising from kidney; the lesion occurred in a 12-year-old girl without tuberous sclerosis. The tumor was widely metastatic to the retroperitoneum and chest, and the patient died of the disease 9 months after diagnosis, despite active chemotherapy. Pigmented epithelioid clear-cell tumor of the kidney is a rare variant of epithelioid angiomyolipoma and a member of the family of perivascular epithelioid cell tumors (PEComas). The tumor demonstrated overlapping features between clear-cell sugar tumor and epithelioid variant of angiomyolipoma. Tumor cells were positive for HMB-45 expression, negative for any evidence of muscular differentiation, and contained melanin pigment and premelanosomes in the cytoplasm. Diffuse C-Kit (CD117) positivity was identified throughout the tumor. This is the first report of C-Kit–positive malignant PEComas.     

PG-M1: A New Monoclonal Antibody Directed against a Fixative-Resistant Epitope on the Macrophage-Restricted Form of the CD68 Molecule

A new anti-macrophage monoclonal antibody (PG-M1) was produced by immunizing BALB/c mice with fresh spleen cells from a patient with Gaucher's disease. PG-M1 reacts strongly with a fixative-resistant epitope of an intracytoplasmic molecule, selectively expressed by virtually all macrophages of the human body. Although attempts to immunoprecipitate the molecule recognized by PG-M1 have failed so far, the reactivity of the antibody with COS-1 and WOP cells transfected with a human complementary DNA clone encoding for the CD68 antigen suggests that PG-M1 is a new member of the CD68 cluster. However, unlike other CD68 antibodies (KP1, EBM11, etc.), which react with both macrophages and myeloid cells, PG-M1 detects a fixative-resistant epitope on the macrophage-restricted form of the CD68 antigen. In 957 routinely fixed, paraffin-embedded samples, PG-M1 showed a more restricted reactivity with elements of the monocyte/macrophage lineage than the previously described monoclonal antibodies MAC-387 (anti-calgranulins), KP1 (CD68) and Ki-M1P. Among hematological malignancies, PG-M1 only labels acute leukemias of M4 and M5 type and rare examples of malignant histiocytosis/true histiocytic sarcoma. In contrast, acute leukemias of the M1, M2, M3, M6, M7, and L1-L3 types, non-Hodgkin's lymphomas, and Hodgkin and Reed-Sternberg cells of Hodgkin's disease are consistently PG-M1-negative. In the daily diagnostic practice, PG-M1 seems to be particularly valuable for the diagnosis of myelomonocytic or monocytic leukemia and neoplasms of true histiocytic origin in routine paraffin sections.     

Squamous carcinoma in situ of the skin containing premelanosomes, with melanocytic colonization of the tumor.

Premelanosomes in nonmelanocytic epithelial neoplasms and "colonization" of nonmelanocytic tumors by melanocytes are two phenomena rarely documented in the literature. We report a squamous carcinoma-in-situ of skin displaying both phenomena. Light microscopy showed clusters of tumor cells in the epidermis, some of which contained melanin. Dendritic melanocytes were admixed with the tumor cells. No ulceration was present. Immunoperoxidase stains for keratin showed no staining of tumor cells. Some nondendritic cells stained for HMB-45, consistent with a melanocytic lesion. Electron microscopy showed two cell types, one with desmosomes, tonofilaments, and premelanosomes and a second dendritic type with only premelanosomes. Premelanosomes were also present free in the intercellular space. These findings suggest that premelanosomes may first be discharged by melanocytes into the intercellular space and are then phagocytosed by the neoplastic cells. Thus the presence of premelanosomes in a tumor cell is not pathognomonic for melanoma or other neural crest tumors.     

Hepatic angiomyolipomas with a deceptive trabecular pattern and HMB-45 reactivity

We report two cases of giant hepatic angiomyolipoma with a prominent component of epithelioid smooth muscle cells exhibiting a distinctive trabecular arrangement. These cells possessed peripherally vacuolated and centrally condensed hyaline cytoplasm. The nuclei were eccentrically placed in the cytoplasm. Immunohistochemically, they expressed HMB-45 intensely in the central condensed cytoplasm and actin in a perimembranous fashion. Staining for desmin, myoglobin and vimentin was negative. HMB-45 may prove to be a sensitive marker for angiomyolipoma with epithelioid cells. Hepatocellular carcinoma and other hepatic tumours with polygonal clear cells can be readily distinguished by these means.     

Lymphangiomyomatosis and angiomyolipoma: closely related entities characterized by hamartomatous proliferation of HMB-45-positive smooth muscle

Angiomyolipoma is a hamartomatous condition which can occur as a component of the tuberous sclerosis complex. Lymphangiomyomatosis, another hamartomatous lesion occurring predominantly in the lungs, has long been suspected to be related to angiomyolipoma and tuberous sclerosis because of occasional clinical associations. We undertook this study to provide further support for the close relationship between these two entities. Five cases of lymphangiomyomatosis and 20 case of angiomyolipoma were retrieved for histological review and immunohistochemical studies. The antibodies used were anti-muscle specific actin (HHF-35), anti-desmin (D33) and antimelanoma (HMB-45). Lesions featuring smooth muscle proliferation were used as controls. The proliferated smooth muscle cells in both lymphangiomyomatosis and angiomyolipoma were much plumper and paler or even clear, when compared with the deeply eosinophilic cytoplasm of the normal spindly smooth muscle cells and those of leiomyomas. Their nuclei were round to oval and pale rather than elongated and dark. Cells with bizarre nuclei were commoner in angiomyolipoma (18/20 cases) than lymphangiomyomatosis (1/5). In 12 cases of angiomyolipoma there were foci indistinguishable from lymphangiomyomatosis, i.e. plump spindle cells arranged in short fascicles around ramifying endothelium-lined spaces. All five cases of lymphangiomyomatosis stained for muscle-specific actin, desmin and HMB-45. For angiomyolipomas, the positivity rates for these markers were: 20/20, 17/20 and 18/20, respectively, including one case that was negative for both desmin and HMB-45. The various smooth muscle proliferations and tumours selected as controls were uniformly HMB-45 negative. The distinctive cytological features, morphological overlap and immunophenotypic profile all support a close relationship between lymphangiomyomatosis and angiomyolipoma, which probably represent different morphological manifestations of hamartomatous proliferation of a peculiar form of HMB-45-positive smooth muscle.