Basaloid squamous cell carcinoma of esophagus expressing KIT: A case report with immunohistochemical analysis

Basaloid squamous cell carcinoma of esophagus (BSCC-E) is rare. This case report is the first demonstrating KIT protein expression of BSCC-E. A 74-year-old man presented with dysphagia. Endoscopy revealed a polypoid tumor (2 × 2 × 2.5 cm) with a stalk in cervical esophagus. Biopsy showed squamous cell carcinoma with undifferentiated areas. An endoscopic submucosal dissection (ESD) was performed. Grossly, it was solid tumor with white cut surface. Histologically, the tumor was hypercellular carcinoma consisting of solid areas of island. The tumor cells were composed of basaloid malignant cells with hyperchromatic nuclei, scant cytoplasm, and basophilic cytoplasm. Many mitotic figures were recognized. Foci of comedonecrosis were scattered. Areas of squamous and glandular differentiations were scattered. Immunohistochemically, the tumor cells were positive for pancytokeratin (PCK) CAM5.2, PCK AE1/3, cytokeratin (CK) 7, KIT, CEA, CA19-9, EMA, Ki-67 (labeling index = 80%). The tumor cells were negative for CK20, PDGFRA, NSE, vimentin, estrogen receptor, p53 protein, chromogranin, synaptophysin, CD56, and TTF-1.