Interstitial Cells of Cajal in Deep Esophageal Leiomyoma

Gastrointestinal stromal tumors (GISTs) are potentially aggressive mesenchymal neoplasms with spindle cell, epithelioid, or mixed morphology. They typically express CD117, DOG1, and CD34 and can be diffusely and strongly positive for h-caldesmon. Leiomyomas are benign smooth muscle neoplasms that can arise in a variety of visceral and soft tissue sites, including the gastrointestinal tract. We illustrate a case of a neoplasm of the gastroesophageal junction that was clinically suspected to be a GIST. Histology showed a tumor composed of ovoid and spindle cells arranged in short intersecting fascicles, which was positive for desmin, smooth muscle actin, and h-caldesmon, with a prominent interspersed subpopulation of CD117- and DOG1-positive elongated or dendritic-like cells. These features were of leiomyoma with entrapped interstitial cells of Cajal (ICC). The recognition of possible entrapment of ICC in leiomyomas as a potential mimic of GIST is important for correct treatment and prognostication.