[P365] A case of CK20 negative Merkel cell carcinoma = [P365] A case of CK20 negative Merkel cell carcinoma

다국어 초록 (Multilingual Abstract)

Merkel cell carcinoma is a rare neuroendocrine tumor that is highly aggressive in nature and indolent in progression. The common risk factors for Merkel cell carcinoma are senility, prolonged exposure to sunlight, immune deficient states and recently, Merkel cell polyomavirus has been characterized to be significantly associated with the pathogenesis of the disease including the expression of CK20. The diagnosis is often difficult since histopathological results require a number of differential diagnosis through immunohistochemical stains with other cutaneous malignancies. A 67-year-old male presented with a solitary dome-shaped erythematous round mass on left upper arm for two months. Initially the lesion was grain-sized but eventually enlarged over two months. Biopsy revealed sheets of lymphoid cells with grouped clusters of darkly stained nuclei and intermittently trabecular projections. immunohistochemical stains revealed positive findings to Ki-67, pan-cytokeratin, synaptophysin, chromogranin, CD 56 and negative results to CK 20, leukocyte common antigen, S-100, HMB45 and thyroid transcription factor-1 and CK 20 negative Merkel cell carcinoma was diagnosed based on the adjuvant immunohistochemical findings. Herein, we present a CK20 negative Merkel cell carcinoma in light of expanding the knowledge of unusally stained immunohistochemial results in Merkel cell carcinoma.