Small cell carcinoma (SCC) of the oral cavity is extremely rare; only one case has been reported in the English Literature. The author herein reports the second case of SCC of the oral cavity. A 59-year-old man presented with oral
tumor (5 cm) in the right cheek mucosa. A biopsy was taken. The HE histology was typical SCC consisting of small epithelial cells with hyperchromatic nuclei, molded nuclei, scant nucleocytoplasmic ratio, and negative nucleoli. Immunohistochemically, the
tumor cells are positive for pancytokeratin (PCK) WSS, PCK MNF-116,
cytokeratin (CK) 34BE12, CK5/6, CK14,
vimentin, KIT (CD117), CD56,
synaptophysin, p53
protein, and
Ki67 antigen (Ki-67 labeling = 70%). The
tumor cells are negative for PCK AE1/3, PSK
CAM5.2, CK7, CK8, CK18, CK19, CK20, EMA, NSE,
chromogranin,
platelet-derived growth factor-α (PDGFRA), CD45, CD45RO, CD3, CD20, CD30, CD79a, and bcl-2. A retrospective genetic analysis using PCR-direct sequencing method in
paraffin sections identified no mutations of KIT (exons 9, 11, 13 and 17) and PDGFRA (exons 12 and 18) genes. Various imaging modalities including CT and MRI and upper and lower gastrointestinal endoscopy did not identified no
tumors other than the oral
tumor. Thus, the oral
tumor was thought primary. The oral
tumor rapidly enlarged, and distant
metastases to cervical lymph nodes, ribs and iliac bones emerged. The patient is now treated by
cisplatin-based
chemotherapy 16 months after the first manifestation.