Muscular metastasis of superficial esophageal squamous cell carcinoma: a rare case of recurrence after endoscopic submucosal dissection with additional chemoradiotherapy.

Esophageal cancer after endoscopic treatment may recur depending on the risk. We present a case of a rare T1b esophageal cancer after endoscopic treatment plus chemoradiotherapy (CRT) that recurred with metastasis of the dorsal muscles. A 70-year-old man was referred for treatment of early-stage esophageal carcinoma. Endoscopic submucosal dissection (ESD) was performed and histopathology showed a poorly differentiated squamous cell carcinoma with invasion to the submucosal layer (sm2) with INFc-type invasion and positive venous invasion. After subsequent CRT, the patient was monitored every 6 months, using computed tomography (CT) and endoscopy. Fifteen months after the treatment, contrast CT revealed a spherical mass with 9 cm ring enhancement within the right erector spinae, that had squamous cell carcinoma confirmed by CT-guided biopsy. Radiation and systemic chemotherapy were initiated for the metastasis of the esophageal carcinoma. However, he died of respiratory failure due to rapid pleural effusion 26 months after ESD. Pathological autopsy showed diffuse squamous cell carcinoma invasion of the cystic wall, forming a lumbar mass, and absence of cancer cell remnants or recurrences in the esophagus. This case report emphasizes the need for systemic observation of superficial esophageal cancer after treatment with a high risk of recurrence.