Abstract
Merkel cell carcinoma (MCC) is a rare cutaneous malignancy. Excessive exposure to sunlight and ultraviolet (UV) radiation, immune suppression and advanced age are the major risk factors for MCC. It typically presents in the head and neck region (50%), followed by extremities (40%) and rarely at other sites (<10%).
In 2008, Merkel cell polyomavirus (MCV) was linked to the development of Merkel cell carcinoma (MCC).
MCC is included in the differential diagnosis of small blue cell neoplasms, composed of monomorphous population of cells with round-to-oval nucleus and scant cytoplasm. The tumor cells co-express epithelial and neuroendocrine markers. ALK (Anaplastic lymphoma kinase) expression is frequently seen in MCC and correlates with the etiopathology of Merkel cell polyomavirus (MCV).
On a retrospective search through our database, we found ten cases of MCC over a period of three years from 2016 to 2019.
Three of the ten cases were at sites of chronic sun exposure. Eight of the ten patients were male. Two of the ten patients had recurrences; one within a year. Five of the ten patients had metastatic disease. All ten cases showed immunoexpression of CK20, Synaptophysin and Chromogranin. ALK-1 expression could be ascertained in six of the cases and was positive in all of them.This case series highlights a relatively uncommon Polyoma virus associated carcinoma. The significance of ALK immunopositivity in MCC, its implied correlation with Merkel cell polyomavirus (MCV) etiopathogenesis and the possibility to use it as a novel therapeutic target needs further exploration.

Key words: Merkel cell carcinoma (MCC), Merkel cell polyoma virus (MCV), ALK (Anaplastic lymphoma kinase)