Abstract

Adenosquamous carcinomas of the intestine are rare tumors, especially when they occur in the small bowel. We report a case of primary adenosquamous carcinoma of the proximal jejunum in a 66 year old woman with no underlying pathologic condition. The tumor mainly consisted of well differentiated squamous cell carcinoma showing keratin pearl and conspicuous intercellular bridges, and minor portion revealed well differentiated adenocarcinoma. The tumor seemed to have originated from the mucosal epithelium, invading the entire wall and metastasizing to the regional lymph nodes. Previous reports of adenosquamous carcinoma of the small intestine have been associated with metastatic disease from distant sites or intestinal duplication. In the colon, squamous cell differentiation have been seen in about 0.05% of adenocarcinomas and in 0.4% of adenomata. The pathogenesis of squamous cell carcinoma of the intestine is unknown, but some possible mechanisms are proposed. :1)malignant transformation of squamous cell epithelium in the submucosa, 2)aberrant differentiation of stem cells to squamous cell with subsequent malignant change, 3)squamous metaplasia of glandular cells with subsequent malignant change, 4)transformation of an adenosquamous into an epidermoid carcinoma.

• Keywords: Adenosquamous carcinoma;Jejunum