Differentiation of reactive and/or atypical mesothelial cells from malignant epithelial cells in serous effusions remains a frequent diagnostic problem. Since epithelial membrane antigen (EMA) positive malignant cells in serous effusions have been reported in almost all adenocarcinomas and most malignant mesotheliomas, immunoreactivity for EMA is felt to be less useful than other antibodies in the workup of problematic serous effusions. However, immunostaining of reactive and/or atypical benign mesothelial cells for EMA has not been well studied, with only a few series reporting either weak or negative staining for EMA. This study was undertaken to evaluate how often reactive and/or atypical appearing mesothelial cells stain positively for EMA. One hundred eighty serous effusions (115 pleural, 55 peritoneal, and 10 pericardial) from 123 females and 57 males ages 20 to 89 yr were evaluated in which an antibody panel including EMA was performed on cell blocks (141 cases), cytospins (36 cases), or both (3 cases). Of the 100 cytologically positive cases, EMA immunoreactivity was present in 97/100 (97%) cases. One EMA negative case suspicious for a metastatic renal cell carcinoma was lost to follow-up and not included in the analysis. The remaining three negative cases consisted of malignancies not expected to have EMA positive cells (small cell carcinoma, neuroblastoma, and synovial sarcoma). Therefore, EMA was positive in virtually 100% of the remaining malignant cases. In the 78 cytologically negative cases, EMA positivity was present in 3/78 (3.8%) cases. Clinical follow-up of up to 14 mo in these three cases revealed no evidence of malignancy.(ABSTRACT TRUNCATED AT 250 WORDS)

The cytologic results of 44 consecutive fine-needle aspiration (FNA) biopsies of the pancreas are reported. The series consisted of 27 women and 17 men with an age range of 31-89 yr (mean, 61.5). Excluding insufficient cases, the sensitivity of the procedure was 88%, specificity was 100%, positive predicative value (PV) was 100%, negative PV was 69%, and efficiency of the test was 90%. There were 29 true-positive, four false-negative, and nine true-negative diagnoses. Two specimens were insufficient for diagnosis. Giant cells of varying types were seen in both the malignant and benign cases. Two of the benign cases demonstrated rare multinucleated foreign body-type giant cells, most likely representing the changes seen in pancreatitis. In 13 malignant cases, multinucleated tumor cells were present, while six additional cases had multinucleated benign histiocytes reflecting the associated pancreatitis. Two malignant cases each had tumor giant cells and benign multinucleated histiocytes. Three of the malignant cases had numerous multinucleated tumor giant cells arranged in a dissociative fashion with evidence of cytophagocytosis consistent with a pleomorphic giant-cell carcinoma of the pancreas. One additional case demonstrated numerous multinucleated osteoclastic-like cells consistent with an osteoclastic tumor of the pancreas. This article documents the accuracy of FNA biopsy of the pancreas and notes that giant cells of varying types can be found in pancreatic FNA biopsies. Appreciation of the various types of giant cells in pancreatic FNA biopsy is important for diagnostic accuracy and prognosis.

"Negative images" of bacilli in mycobacterial infections have been recently described in air-dried, Romanovsky-stained cytologic material. We report a case of negative images due to crystalline deposition of clofazimine, a drug used to treat Mycobacterium avium-intracellulare complex infection in AIDS patients. The negative images of clofazimine crystals seen in bronchoalveolar lavage (BAL) macrophages resemble the negative images of mycobacterial infection due to the pseudogaucher appearance of the cells. Crystals are distinguished by their refractile reddish appearance in unfixed, unstained smears, and by their birefringence on polarization. Crystals were found in both Pap-stained and Diff-Quik-stained smears and were negative with Ziehl-Neelsen stains. Clofazimine crystals in BAL specimens must be distinguished from the pseudogaucher type cells of mycobacterial infection in this patient population. We believe that this is the first report of clofazimine crystal deposition diagnosed in a BAL specimen along with electron microscopic examination of the cytologic material.

We reviewed 51 serous effusions (50 peritoneal/one pleural) from 38 patients with uterine (30 cases) and ovarian (eight cases) malignant mixed Müllerian tumors (MMMT). There were 16 patients (42%) with positive effusion cytology specimens; 13 cases (81%) were diagnosed as adenocarcinoma with three cases (19%) interpreted as having a sarcomatous component. Eight of 16 positive effusion specimens had cell block material available for immunoperoxidase (IP) study that included cytokeratin (AE1/3), vimentin, muscle specific actin (HHF) and S-100 protein to determine if unsuspected mesenchymal components were present in the cases originally diagnosed as carcinoma (six cases), or sarcomas (two cases). In the six cases originally interpreted as carcinoma, three were diagnosed as adenocarcinoma and three as poorly differentiated carcinoma. All three of the cases considered adenocarcinoma and two of those diagnosed as poorly differentiated carcinoma reacted only with AE1/3 and vimentin. The remaining case, considered a poorly differentiated carcinoma, stained only with vimentin. In the two cases having cell blocks interpreted as having a sarcomatous component, only vimentin was positive in one while AE1/3, vimentin, HHF, and S-100 were positive in the other. The case where all immunohistochemical stains were reactive contained both carcinomatous and sarcomatous components. In the three cases considered sarcomatous, the cytomorphologic features helpful in the recognition of a mesenchymal component included a dissociated smear pattern of pleomorphic round to oval cells and/or spindle cells. In retrospect, the IP stains did not alter any of the original diagnoses.(ABSTRACT TRUNCATED AT 250 WORDS)