INTRODUCTIONMerkel Cell Carcinoma (MCC) is a rare, life-threatening tumor with neuroendocrine features. Due of its extremely low occurrence worldwide, epidemiological data on the disease is limited. (1). Commonly recognized risk factors include fair skin, history of skin cancer, old age, chronic immunosuppression, chronic ultraviolet (UV) light exposure, and Merkel cell polyomavirus (MCPyV) infection (2). Amongst these factors, MCPyV and UV exposure play a fundamental role with synergistic effects in the pathophysiology of MCC (3). Despite being a part of normal skin flora in most individuals, MCPyV DNA can clonally combine with the genome of neoplastic cell precursors at the initial phases of carcinogenesis (4, 5). Concurrently, UV exposure elicits antigen-presenting dendritic cells to produce inflammatory cytokines, leading to local immunosuppression and creating an ideal environment for tumoral growth (6). Moreover, immune hypersensitivity from UV exposure facilitates the viral tumorigenic process (2).Merkel cells cannot be derived from the MCC because they lack the ability to proliferate. Merkel cell precursors (perhaps generated from epidermal stem cells or hair follicle stem cells) and pre- and pro-B cells appear to have histopathology, genetics, and molecular characteristics with malignant cells instead (7).MCC often presents as a single, asymptomatic erythematous or violaceous nodule, often mistaken for cysts or abscesses. It usually originates from the head or neck and generally spares the extremities (8). Immunohistochemical (IHC) staining is required to validate histopathological findings of small round cells that infiltrate cutaneous or subcutaneous area. (7). Although MCC responds to the combination of excisional surgery, radiotherapy, and chemotherapy, it requires continuous follow-ups within the first year of diagnosis due to the high recurrence rate (9).Here, we present a 32-year-old Iranian (non-Caucasian) immunocompetent female with a small nodule on her left arm at the disease onset finally diagnosed as MCC. In this report, we aim to emphasize the significance of early diagnosis and management of this cancer and highlight the complications that a late diagnosis would entail for these patients.