Challenges and limitation of MTAP immunohistochemistry in diagnosing desmoplastic mesothelioma/sarcomatoid pleural mesothelioma with desmoplastic features

AimGenomic-based ancillary assays including immunohistochemistry (IHC) for BRCA-1 associated protein-1 (BAP1) and methylthioadenosine phosphorylase (MTAP), and fluorescence in situ hybridization (FISH) for CDKN2A are effective for differentiating pleural mesothelioma (PM) from reactive mesothelial proliferations. We previously reported a combination of MTAP and BAP1 IHC effectively distinguishes sarcomatoid PM from fibrous pleuritis (FP). Nevertheless, cases of sarcomatoid PM with desmoplastic features (desmoPM) are encountered where the IHC assessment is unclear.Methods and resultsWe evaluated assessment of MTAP IHC, BAP1 IHC, and CDKN2A FISH in 20 desmoPM compared to 24 FP. MTAP and BAP1 IHC could not be assessed in 11 (55 %) and 10 (50 %) cases, respectively, due to loss or faint immunoreactivity of internal positive control cells, while CDKN2A FISH could be evaluated in all cases. The sensitivities for MTAP loss, BAP1 loss, and CDKN2A homozygous deletion in desmoPM were 40 %, 10 %, and 100 %. A combination of MTAP loss and BAP1 loss yielded 45 % of sensitivity.ConclusionsMTAP IHC is a useful surrogate diagnostic marker in differentiating ordinary sarcomatoid PM from FP, but its effectiveness is limited in desmoPM. CDKN2A FISH is the most effective diagnostic assays with 100 % sensitivity and specificity in discriminating desmoPM from FP in the facilities where the FISH assay is available.     

Algorithm for cytological diagnosis of nonneoplastic lesions of the salivary glands

The aim of this study was to formulate an algorithm for the cytologic diagnosis of nonneoplastic enlargements of the salivary gland.Smear cellularity and cytological features such as presence of epithelial cells and types of inflammation were assessed in a retrospective study of 201 aspirates. One hundred and forty-six were inflammatory, 19 were noninflammatory nonneoplastic, and 36 were cystic lesions. Of the cystic lesions, cytological evidence of retention cyst was seen in seven, while two aspirates with only hemosiderin-laden macrophages were hematomas. The remaining 27 defied subclassification. Noninflammatorynonneoplastic lesions included 5 fatty infiltrations, 2 sialadenosis, and 12 normal salivary glands. Forty-two lesions were acute inflammations, 89 were chronic, and 15 were granulomatous. Cytomorphologic patterns identified in samples with acute inflammation were 9 abscesses, 29 acute obstructive sialadenitis, and 4 acute infective sialadenitis. Three aspirates with chronic inflammation were lymphoepithelial lesions, 82 chronic sialadenitis, and 4 lymph node in salivary gland. Fifteen granulomatous lesions were 10 tuberculosis, 3 sarcoidosis, and 2 foreign body granulomas. Using the proposed algorithmic approach, nonneoplastic salivary gland enlargement could be placed into distinct, clinically relevant diagnostic categories.     

Chordoma. Antibodies to epithelial membrane antigen and carcinoembryonic antigen in differential diagnosis

Seven chordomas, chondrosarcomas, and mucinous colorectal carcinomas, five liposarcomas, and five ependymomas were evaluated for the presence of epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA) by using an immunoperoxidase technique. All of the chordomas and mucinous carcinomas were cytoplasmic EMA positive, while the chondrosarcomas, liposarcomas, and ependymomas were negative. Among the tumors that were studied, only the mucinous carcinomas were positive for CEA. The EMA positivity of a chordoma reflects its epithelial nature and is a valuable aid in making the differential diagnosis between a chordoma and nonepithelial tumors, while the absence of CEA in a chordoma aids in making the distinction between a chordoma and a mucinous carcinoma.     

Distribution of epithelial membrane antigen in benign and malignant lesions of the salivary glands

Summary An antiserum against epithelial membrane antigen has been used to stain a variety of lesions arising in the salivary glands. In normal major and minor glands staining was localised to the ductal systems. There was no evidence of myoepithelial cell staining. The mucous elements of the submandibular and sublingual glands were negative, but in the mucous elements of the minor glands there was focal cytoplasmic positivity. There was no cytoplasmic staining of serous elements in major or minor salivary glands. In pleomorphic adenomas the luminal membrane of ductal elements was strongly positive, with focal cytoplasmic positivity in some myxoid areas. In mucoepidermoid tumours both adjacent cell membranes and cytoplasm were strongly positive. The ductal structure of adenoid cystic carcinomas were clearly delineated while the pseudoducts produced by enclosed areas of stroma were negative. All mesenchymally derived tumours were negative and a tumour previously considered as a chondroma was strongly positive. The results are discussed in relation to phenotypic heterogeneity and the histogenesis of salivary gland tumours.     

Identification of novel markers for the diagnosis of malignant pleural mesothelioma

The diagnosis of malignant pleural mesothelioma is difficult, with the most common differential diagnoses being benign pleural diseases and metastatic adenocarcinomas (ADCA). To identify novel markers that would be able to improve diagnostic accuracy, we performed a genome-wide gene expression analysis on tumor cell lines established from pleural effusions (malignant pleural mesothelioma and lung ADCA). This analysis led to the identification of genes encoding novel and pertinent cellular and soluble markers, for which the expression was validated by real-time RT-PCR. Immunohistochemical staining of tumor biopsy specimens with anti-type III collagen antibodies showed positive labeling for mesothelioma cells but not for ADCA cells. Using enzyme-linked immunosorbent assay, we showed that the C-C motif chemokine 2 (CCL2) concentration was significantly higher in pleural effusions from patients with mesothelioma (n = 61) than in subjects with ADCA (n = 25) or with benign pleural effusions (n = 15): median (interquartile range) = 2.99 ng/ml (1.76 to 6.01) vs 0.99 ng/ml (0.51 to 1.83) and 1.47 ng/ml (0.80 to 1.56), respectively, P < 0.0001. Conversely, the galectin-3 concentration was lower in mesothelioma: 11.50 ng/ml (6.73 to 23.53) vs 24.74 ng/ml (20.42 to 70.35) and 17.64 ng/ml (14.81 to 24.68), respectively, P < 0.0001. The areas under the curve for CCL2 were 0.8030 and 0.7716 for the differentiation of mesothelioma from ADCA or benign pleural effusions, respectively. Similarly, the areas under the curve obtained for galectin-3 were 0.7980 and 0.6923, respectively. In conclusion, type III collagen, CCL2, and galectin-3 are promising new diagnostic markers for mesothelioma.     

Effusion cytology in the diagnosis of malignant epithelioid and biphasic pleural mesothelioma

We reviewed the cytologic findings in pleural effusions of 36 patients in whom a diffuse epithelioid or biphasic malignant mesothelioma of the pleura developed between 1978 and 1988. Malignant neoplasms were diagnosed in 26 (72%) of the 36 patients. A specific diagnosis of a mesothelioma was rendered or suspected in 64% (23/36 patients). Mesothelioma was favored over adenocarcinoma in 81% (29/36) of patients with positive fluid cytologic findings. The contribution of effusion cytology to the final diagnosis and patient treatment was assessed. These data suggested that a cytologic diagnosis contributed useful information in most patients with malignant epithelioid and biphasic pleural mesotheliomas.     

Keratin protein immunoreactivity of sarcomatoid and mixed types of diffuse malignant mesothelioma: an immunoperoxidase study of 30 cases

To define the role of keratin protein immunohistochemistry in the pathologic diagnosis of the sarcomatoid type of diffuse malignant mesothelioma (DMM), we examined 30 DMM (16 pure sarcomatoid type and 14 mixed sarcomatoid-epithelial type) by an indirect immunoperoxidase technique using three commercially available antibodies to keratin proteins. The sarcomatoid (spindle-cell) areas of all 30 cases of sarcomatoid DMM were immunoreactive for keratin proteins. In 14 of 16 cases of sarcomatoid DMM, 50% or more of the tumor cells were reactive with one or more antibodies; however, polyclonal bovine muzzle and monoclonal AE1/AE3 antibodies were distinctly superior to polyclonal human callus keratin antibody in the detection of spindle tumor cells. In contrast with the staining patterns observed for DMM, 39 spindle-cell malignancies and tumor-like processes of 10 histogenetic types were unreactive with the three antibodies. Those spindle-cell tumors and reactive mesothelial proliferations that may enter into the differential diagnosis of sarcomatoid DMM are discussed. We conclude that keratin protein immunohistochemistry is a sensitive and highly useful method for the pathologic diagnosis of the sarcomatoid type of DMM and its distinction from other spindle-cell neoplasms.     

The concept of mesothelioma in situ: implications for diagnosis and histogenesis.

The concept of mesothelioma in situ is explored by a detailed examination of seven patients, subsequently proven to have pleural malignant mesothelioma, who initially had no evidence of gross tumor and for whom biopsy material was available at this early presentation. The tissue was assessed by routine microscopy, the immunoperoxidase technique for epithelial membrane antigen and silver staining for nucleolar organizer regions. Tiny lesions of the pleura that merged with or were adjacent to microscopically flat monolayered or folded mesothelium with cytological atypia were observed. The atypical cells reacted positively to epithelial membrane antigen, and the nucleolar organizer region counts were elevated. These observations are considered to support the possibility of the presence of mesothelioma in situ. These findings are discussed in the light of the proposed concept of mesothelioma in situ, its histogenesis, and its possible clinical relevance.     

Immunoreactivity for cytokeratin and epithelial membrane antigen in leiomyosarcoma

Thirty-three leiomyosarcomas (LMS), which were verified by electron microscopy and by desmin and muscle actin immunoreactivity, were immunohistochemically evaluated for the presence of cytokeratin and epithelial membrane antigen (EMA) with monoclonal antibodies. None of the tumors showed any epithelial component by structure; all were homogeneous spindle cell neoplasms. Cytokeratin immunoreactivity was found in 14 of 33, and EMA in 20 of 33 LMS, usually in a large number of tumor cells. One case was confirmed as cytokeratin-positive in frozen sections with four different monoclonal antibodies. These results show that immunoreactivity for epithelial markers can be present in pure smooth-muscle sarcomas. Thus, such immunoreactivity cannot be regarded as a specific feature of carcinomas, synovial sarcoma, or epithelioid sarcoma, which are already known to be cytokeratin- and EMA-positive.     

The value of epithelial membrane antigen expression in separating benign mesothelial proliferation from malignant mesothelioma: a comparative study

Differentiating reactive mesothelial (RM) proliferation from malignant mesothelioma (MM) can be cytologically challenging. There have been discordant studies reporting the value of epithelial membrane antigen (EMA) in differentiating RM from MM. In this study, we investigated the expression of two different clones of EMA in RM and MM. Twenty cases of pleural effusion smears of RM and 20 cases of MM with their corresponding cell blocks were retrieved from the hospital computer system. Diagnosis of MM was confirmed by surgical decortication or pneumonectomy with immunostaining studies and/or electron microscopy. Cases of RM were confirmed by clinical history and histology. Cell blocks were formalin-fixed, paraffin-embedded, and immunostained for EMA clone Mc5 and EMA clone E29. The positive rates for clone Mc5 were 14/20 (70%) for MM and 12/20 (60%) for RM and EMA clone E29 were 15/20 (75%) for MM and 0/20 (0%) for RM. The sensitivity and specificity for EMA clone Mc5 were 70 and 40%, respectively. For EMA clone E29, the sensitivity and specificity were 75 and 100%, respectively. In conclusion, both RM and MM immunostained for EMA clone Mc5, indicating that it is not a reliable immunocytochemical marker for differentiating RM from MM. EMA clone E29 was negative in all cases of RM and positive in 75% of MM and therefore is a reliable immunocytochemical marker for differentiating RM from MM.     

The utility of epithelial membrane antigen and vimentin in the diagnosis of chromophobe renal cell carcinoma

We evaluated the immunohistochemical expression of epithelial membrane antigen (EMA) and vimentin (VMT) in chromophobe renal cell carcinoma (CHRCC). We also studied the utility of EMA and VMT immunostains in helping differentiate CHRCC from renal oncocytoma and conventional (clear cell) renal cell carcinoma with granular morphology (GCRCC). Immunohistochemical staining for EMA and VMT was performed on 21 cases of CHRCC, 16 cases of renal oncocytoma, and 28 cases of GCRCC. The diagnosis in all cases was by concurrence of all pathologists involved in the study and was based entirely on examination of routinely stained slides. All cases were classic examples of these tumor types and presented no diagnostic difficulties. The intensity of immunohistochemical staining was graded on a scale of 0 to 3 (0 = no staining; 1 = equivocal; 2 = unequivocal, moderate intensity; and 3 = unequivocal, high intensity). Positive immunohistochemical staining was defined as unequivocal staining of at least 20% of the neoplastic cells. All cases of CHRCC were positive for EMA and negative for VMT. The same immunophenotype was observed in 75% of renal oncocytoma and 21% of GCRCC. In summary, all CHRCC cases in our study demonstrated immunohistochemical staining for EMA and not VMT. However, we also found that the same immunophenotype is observed in 75% of renal oncocytoma and in 21% of GCRCC, precluding its utility for positive identification of CHRCC. Nevertheless, the lack of such an immunophenotype is a reliable indication that a neoplasm under consideration is not CHRCC.     

D2-40: a reliable marker in the diagnosis of pleural mesothelioma.

OBJECTIVE: Malignant mesotheliomas of the pleura, peritoneum and pericardium can easily be confused with either metastatic adenocarcinomas or reactive pleural lesions. D2-40, a monoclonal antibody used as a marker for seminomatous germ cell tumours and lymphatic endothelial cells, was recently described in mesothelial cells and type I but not type II pneumocytes. METHOD: The immunoreactivities of D2-40 in 76 lung carcinomas of different histological types (adenocarcinomas, squamous cell, small cell, and bronchioloalveolar carcinomas) were compared with those of 36 pleural epithelioid and sarcomatoid mesotheliomas and 5 specimens of chronic pleuritis. RESULTS: While all 18 analysed epithelioid mesotheliomas displayed a strong membranous immunostaining, 18 sarcomatoid mesotheliomas showed no, or a merely faint, cytoplasmic signal, comparable with fibroblasts in chronic pleuritis. Out of all analysed lung carcinomas, 49 showed no immunoreactivity for D2-40 (64%), while the other 27 (36%) showed a focal weak to moderate and only cytoplasmic signal. CONCLUSIONS: We regard D2-40 as a valid marker in the differential diagnosis of epithelioid mesotheliomas versus pulmonary adenocarcinomas. However, this marker may not properly label sarcomatoid mesotheliomas or distinguish them from reactive pleural lesions.     

Keratin, luminal epithelial antigen and carcinoembryonic antigen in human urinary bladder carcinomas. An immunohistochemical study

14 urinary bladder carcinomas of all main types were investigated with antisera to "broad spectrum keratin" (aK), "luminal epithelial antigen" (aLEA) and carcinoembryonic antigen (aCEA), using an indirect immunoperoxidase method on formalin fixed paraffin embedded sections. Keratin and LEA were both present in normal transitional epithelium, papilloma and carcinoma in situ whereas CEA was absent. Transitional cell carcinomas reacted with both aK and aLEA whereas CEA was seen only in a few foci. In squamous metaplasia and squamous carcinoma reaction with aK was particularly strong, while LEA was almost lacking and CEA was present in necrotic centres. In adenocarcinomas aK and aLEA reacted equally while aCEA reacted only on the surface.