Endoscopic Ultrasound (EUS)-Based Multimodal Diagnosis of a Rare Intramural Esophageal Squamous Cell Carcinoma: Case Report and Literature Review.

Esophageal squamous cell carcinoma (ESCC) is the most prevalent histological subtype of esophageal cancer worldwide, typically manifesting as an endoluminal mass with overt mucosal involvement. Exceptionally, however, ESCC may present with an intramural growth pattern beneath an apparently intact mucosal surface, a presentation that is exceedingly rare and prone to misdiagnosis. In such cases, repeated endoscopic biopsies are frequently non-diagnostic, thereby delaying appropriate management. Endoscopic ultrasound (EUS) has emerged as the cornerstone for detecting and characterizing intramural lesions, enabling assessment of tumor infiltration depth and nodal status, while complementary imaging with CT and PET contributes to accurate staging. To date, only a handful of intramural ESCC cases have been described, and their clinical, endoscopic, and radiological features remain poorly delineated. This review appraises the existing literature on primary intramural ESCC with intact mucosa, with the dual aims of summarizing the diagnostic challenges and highlighting the value of a multimodal approach to avoid unnecessary surgical interventions. Furthermore, we report an additional case from our experience, which underscores the critical role of EUS and integrated imaging in achieving timely and accurate diagnosis of this unusual entity.