Microscopic examination showed a large tumor composed of poorly differentiated, small, round, blue cells that were arranged in a rosette pattern in some areas. Numerous mitotic figures were present. Individual cells had scanty cytoplasm and powdery chromatin. The tumor was thought to be of neuroendocrine origin. Two diagnoses were considered: metastatic or primary oat cell carcinoma and MCC. Special stains were negative for neuron-specific enolase, chromogranin, and synaptophysin. Immunohistochemical studies were positive for cytokeratin 20 and negative for cytokeratin 7, thus confirming the diagnosis of MCC.
A Large Friable Tumor Overlying the Left Side of the Mandible—Diagnosis. Arch Dermatol. 2004;140(5):609-614. doi:10.1001/archderm.140.5.609-b