The cytomorphologic spectrum of small-cell carcinoma and large-cell neuroendocrine carcinoma in body cavity effusions: A study of 68 cases

BACKGROUND: Small-cell carcinoma (SCC) and large-cell neuroendocrine carcinoma (LCNEC) are uncommon in serous body cavity effusions. The purpose of this study is to examine the cytomorphological spectrum of SCC and LCNEC in body cavity serous fluids. MATERIALS AND METHODS: We have 68 cases from 53 patients who had metastatic SCC or LCNEC diagnoses. All cytology slides and the available clinical data, histological follow-up, and ancillary studies were reviewed. RESULTS: A total of 68 cases (60 pleural, 5 peritoneal, and 3 pericardial effusions) from 53 patients with an average age of 73 years (age range 43-92 years) were reported as diagnostic or suspicious of SCC (52 cases) or LCNEC (16 cases). The primary site was lung in 56 cases, pancreas in 6 cases, and 2 cases each from cervix, colon, and the head and neck region. Of the 68 cases, 48 cases had no history of malignancy of the same type. Ancillary studies were used in 46 cases (68%) including flow cytometric studies in 5 cases. There were three predominant cytomorphological patterns observed including small-cell clusters with prominent nuclear molding (33 cases, 49%), large-cell clusters mimicking non-small-cell carcinoma (18 cases, 26%), and single-cell pattern mimicking lymphoma (17 cases, 25%). Significant apoptosis was seen in 22 cases (33%) and marked tumor cell cannibalism was seen in 11 cases (16%). Nucleoli were prominent in 16 cases (24%). The most frequent neuroendocrine markers performed were synaptophysin and chromogranin. CONCLUSIONS: The most common cytomorphologic patterns seen in body cavity effusions of SCC and LCNEC were small-cell clusters with nuclear molding. However, in 51% of the cases either a predominant single-cell pattern mimicking lymphoma or large-cell clusters mimicking non-small carcinoma were noted. In our experience, effusions were the first manifestation of disease in the majority of patients diagnosed with neuroendocrine carcinoma. Therefore, familiarity with the cytomorphological spectrum of neuroendocrine carcinomas in fluid cytology may help in rapidly establishing an accurate diagnosis and in directing appropriate management.