Primary Merkel cell carcinoma of the oral mucosa in a young adult male: Report of a rare case.

ABSTRACT

Merkel cell carcinoma (MCC) is a highly aggressive neoplasm of skin with neuroendocrine differentiation. Primary MCC of the oral mucosa is exceedingly rare and even more unresponsive to therapy. A 15-year-old male presents with gradually increasing painless swelling in right side of the fl oor of mouth for 6 weeks. Computed tomography of head and neck region showed globular mass (4.6 cm × 1.7 cm) involving right side of the fl oor of mouth. Fine-needle aspiration from the upper deep cervical node suggested small round cell tumor. A trucut biopsy showed mass composed of trabeculae and nests of tumor cells with high NC ratio, granular speckled chromatin, scanty to moderate amount of clear vacuolated cytoplasm. Cells were immunoreactive for cytokeratin-20, CD56, c-kit, CD99 and negative for p63, thyroid-transcription factor-1, CDX2, synaptophysin, neuron-specifi c enolase. Patient was started on chemotherapy with cyclophosphamide, doxorubicin and vincristine. The mass regressed in size and patient underwent wide local excision with pull-through approach. Patient is currently under combined chemoradiation regime and doing well.