Primary Esophageal Intramural Squamous Cell Carcinoma Masquerading as a Submucosal Tumor: A Rare Presentation of a Common Disease.

Esophageal squamous cell carcinoma (ESCC) is the commonest primary malignant esophageal tumor, which typically presents as endoscopically visible surface mucosal ulcerations, irregularities, or polyploidal masses. We here report a rare case of primary ESCC with completely intramural growth under a normal looking intact nondysplastic surface squamous epithelium disguising as a submucosal tumor. Upper gastrointestinal endoscopy-guided mucosal biopsy was negative for malignancy. Endoscopic ultrasound (EUS) revealed a heteroechoic solid mass originating from the muscularis propria of the distal esophagus. Cytological study of EUS-guided fine needle aspiration from the mass was suggestive of squamous cell carcinoma, which was confirmed on immunohistochemistry. There was no evidence of metastatic origin of this tumor or continuous cancer involvement from the surrounding structures, including the head, neck, and lungs on bronchoscopy, computed tomography scan, and positron emission tomography scan. Exclusive intramural squamous cell carcinoma with normal overlying mucosa is an exceedingly rare presentation of primary ESCC with only four cases reported in the literature so far. A high index of suspicion is required by the gastroenterologists and pathologists in diagnosing these cases as these tumors closely mimic the mesenchymal submucosal tumors such as lipoma, leiomyoma, and gastrointestinal stromal tumors. EUS is an indispensable tool in making a preoperative diagnosis and therapeutic decision making.