Fine-needle aspiration cytology of recurrent Merkel cell carcinoma of eye-brow

Merkel cell polyomavirus is implicated in a subset of Merkel cell carcinomas, in the Indian subcontinent

Merkel cell carcinoma is a rare, lethal cancer histopathologically composed of cells showing similarity with mechanoreceptor Merkel cells. Merkel cell tumors manifest in two distinct forms. While a virus called Merkel cell polyomavirus is involved in the pathogenesis of one form of Merkel tumors, the other is driven by ultraviolet (UV)-linked mutations. In this study we investigated 18 cases, from the Indian population, of Merkel cell carcinoma for immunohistochemical (IHC) expression of Merkel cell polyomavirus (MCV) T antigen, including 12 cases tested by PCR, to identify viral etiopathology. We tested the tumors with two sensitive antibodies (CM2B4 and Ab3), targeting the viral large T antigen protein and with PCR primers targeting the N terminus of T antigen. Overall, we observed 38.8% (7/18) tumors displaying positive IHC expression of Merkel cell polyomavirus T antigen and 25% (3/12) tumors showing positive results, by both, immunohistochemistry and PCR. This constitutes the first report from India showing implication of MCV in Merkel cell carcinomas. Moreover, this is one of the larger series of Merkel cell carcinomas, tested for MCV, by both immunohistochemistry and PCR, in this part of the world. These results further indicate that a slightly more number of such cases in India are likely to be caused by UV-linked damage, as opposed to Merkel cell polyomavirus mediated tumorigenesis, which is definitely implicated in a subset of cases.

Cytological and Immunocytochemical Features of Merkel Cell Carcinoma on Fine Needle Cytology Samples: A Study of 22 Cases

Merkel cell carcinoma (MCC) is an uncommon neuroendocrine small cell tumor derived from the transformation of the homonymous cells in the basal layer of the epidermis. MCC has a generally aggressive course, with a high tendency for local recurrence, lymph node involvement, and distant metastasis. Fine needle cytology (FNC) and immunocytochemistry were used as diagnostic procedures for 22 cases of MCC presented at our institute. All cases of MCC were successfully diagnosed on FNC. Among all of the monoclonal antisera used (CD56, CK20, CK MNF116, neuron-specific enolase (NSE), synaptophysin, and chromogranin), NSE and CD56 showed the highest frequency of positivity. The accuracy of the cytological diagnosis was 100% compared to the corresponding previous or subsequent pathological diagnoses. FNC and immunocytochemistry represent excellent and accurate diagnostic methods to distinguish MCC from other small-cell malignant entities.