Case Report: The leiomyoma-leiomyosarcoma sequence exists in the esophagus: first case of malignant transformation treated with endoscopic submucosal dissection.

OBJECTIVES: Esophageal leiomyosarcoma (ELMS) is an extremely rare malignant tumor, and the possibility of malignant transformation from benign esophageal leiomyoma has historically been dismissed. This report presents, to our knowledge, the first documented case of malignant transformation within an esophageal leiomyoma and its successful treatment via endoscopic submucosal dissection (ESD), challenging the conventional belief regarding the absolute benignity of esophageal leiomyomas.

CASE SUMMARY: A 52-year-old female presented with non-specific symptoms and was found to have a small (0.8 cm) esophageal submucosal nodule during gastroscopy. Endoscopic ultrasound (EUS) showed a well-defined hypoechoic lesion originating from the submucosal layer. The lesion was completely resected via ESD. Histopathological examination demonstrated a conventional leiomyoma with a focal area of malignant transformation to leiomyosarcoma, characterized by high cellularity, nuclear atypia, increased mitotic activity [5 per 2 high-power fields (HPF)], elevated Ki-67 index (40%), and loss of smooth muscle markers (SMA, desmin) in the malignant region. Surgical margins were tumor-free. The patient recovered well with no recurrence at 60-day follow-up.