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Int J Clin Exp Pathol 2013;6(6):1164-1168

Case Report
Primary cutaneous small cell carcinoma; a case report with differential diagnosis

Tadashi Terada

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

Received March 2, 2013; Accepted March 29, 2013; Epub May 15, 2013; Published June 1, 2013

Abstract: Primary cutaneous small cell carcinoma (PC-SmCC) is extremely rare; only two cases have been reported in the world literatures. A
79-year-old woman presented a small cutaneous tumor in the face. Physical examination showed a tumor measuring 1.0x.08x0.6 cm in the
shallow skin of the face. Excisional skin biopsy was performed. The biopsy showed complete excision of the tumor. The tumor was located in
the shallow dermis and no connections to epidermis were seen. The tumor was invasive into subcutaneous tissue and surrounding dermis.
The tumor was very hypercellular tumor composed of small cells with scant cytoplasm, hyperchromatic nu lei, negative nucleoli, and molded
nuclei. The shapes of tumor cells are round, ovoid or spindle. The histological appearances fulfilled the criteria of SmCC of WHO.
Immunohistochemically, the tumor cells were positive for cytokeratin (CK) AE1/3, CK CAM5.2, CK34BE12, CD5, CD6, CK8, p63, NSE, NCAM,
synaptophysin (focal), chromogranin (focal), p53, KIT, PDGFRA and Ki-67 (labeling index (LI)=86%). They were negative for CK7, CK19, CK20,
EMA, vimentin, CEA, S100 protein, CA19-9, TTF-1, MUC1, MUC2, MUC5AC and MUC6. Mucin histochemistry revealed no mucins. A molecular
genetic analysis of PCR-direct sequencing identified no mutations of KIT (exons 9, 11, 13, and 17) and PDGFRA (exons 12 and 18) genes. The
author diagnosed this cutaneous tumor as SmCC. Post-diagnosis whole body examination using various imaging and endoscopic techniques
revealed no tumors. This may confirm that the skin tumor was primary. The cutaneous tumor was completely resected with wide margins. The
patient is now followed up without therapy 8 months after the diagnosis. No recurrence or metastasis is seen. The differential diagnosis from
Merkel cell carcinoma and basal cell carcinoma is very difficult and herein discussed. (IJCEP1303004).

Keywords: Skin, small cell carcinoma, basal cell carcinoma, Merkel cell carcinoma

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