Collision Tumor at the Gastroesophageal Junction; Coexistence of Basaloid Squamous Cell Carcinoma and Small Cell Neuroendocrine Carcinoma

Basaloid squamous cell carcinoma (BSC) is a poorly differentiated and rare variant of squamous cell carcinoma. It is frequently seen in the upper respiratory and gastrointestinal systems. Neuroendocrine tumors originate from the neuroendocrine system and may be seen at any site of the body. Small cell neuroendocrine carcinoma (NEC) belongs to the poorly differentiated neuroendocrine tumor group, and tumors can be located at various sites, most commonly occurring in the lungs. In light of the current literature on these carcinomas, this case study reports a 61-year-old male in whom these poorly differentiated tumors were found to coexist. To the best of our knowledge, coexistence of BSC and small cell NEC at the gastro-esophageal junction is quite a rare condition and the first case report in the literature. In this case report, coexistence of two poor-differentiated tumors has been discussed under the light of the current literature.