Merkel Cell Carcinoma: A Case-Report of Rare Presentation of Merkel Cell Carcinoma, Non-Indolent Proliferative Type, Polyomavirus-Negative: Hypothesis of MolecularPathogenesis

Introduction: Merkel cell carcinoma (MCC) is a rare cutaneous indolent neuroendocrine cancer, arising from the Merkel cells of the stratum basalis, of the epidermis. This type of tumor commonly arises in sun-exposed areas, such as head, neck, and lower extremities. Here, we describe a rare presentation of non-indolent proliferative type Merkel cell carcinoma. Case Report: This is a case-report of a 70-year-old Caucasian man with no pertinent past medical history, presenting as a large painless violaceous necrotic irregular bordered rapidly growing lesion, reaching to 8x10x15 cm3, within one-year period, on the lower back region with surface ulceration. Pelvic MRI showed a multilobulated enhancing soft tissue mass measuring 8.7x10.4x15.1 cm3 at the left gluteal region with exophytic extension to the left paraspinal muscles. The patient was admitted, tangential surgical excision and debridement of left flank wound was performed with partial primary closure. Pathology showed features of Merkel cell, show diffuse dot-like positivity with CK20 and are negative for CK7, there is diffuse positivity with NSE, synaptophysin and CD56 with strong diffuse Ki-67 positivity noted in >65% of tumor cells. CD99 shows diffuse small faint dot-like paranuclear positivity. Discussion: Merkel cell carcinoma (MCC) is a rare, aggressive tumor that generally arises in sun-exposed regions. After an initial course of slow growth, starting as a painless violaceous non-pruritic domed-shaped lesion, the tumor becomes more aggressive, rapidly growing, with metastasis with local lymph nodes and regional tissue invasion. Sixty percent of tumors can rapidly grow within a three-month period after initial diagnosis. MCC is also clonally associated with is polyomavirus. MCC Contributing molecular pathogenesis is imperative to determining the causation of rare non-indolent MCC tumors, and its association with prognosis and treatment. In polyomavirus negative patients, consideration for molecular pathogenesis as etiology is imperative.