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Int J Clin Exp Pathol 2013;6(4):780-787

Case Report
Small cell carcinoma of the oral cavity (cheek mucosa): a case report with an
immunohistochemical and molecular genetic analysis

Tadashi Terada

Department of Pathology, Shizuoka City Shimizu Hospital, Shizuoka, Japan

Received December 11, 2012; Accepted February 15, 2013; Epub March 15, 2013; Published April 1, 2013

Abstract: 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, plate-let-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. (IJCEP1212016).

Keywords: Oral cavity, cheek mucosa, small cell carcinoma, histopathology, immunohistochemistry, molecular biopsy of KIT and PDGFRA

Address correspondence to: Dr. Tadashi Terada, Department of Pathology, Shizuoka City Shimizu Hospital, Miyakami 1231 Shimizu-Ku, Shi-
zuoka 424-8636, Japan. Tel: 81-54-336-1111; Fax: 81-54-336-1315; E-mail: piyo0111jp@yahoo.co.jp