Colonic Granular Cell Tumor: An Endoscopic and Histopathologic Review with Case Illustration.

Granular cell tumors (GCTs) are rare and benign tumors that can occur at any anatomical site. GCTs are thought to originate from nerve cells, particularly Schwann cells. Their name derives from the fact that an accumulation of cytoplasmic lysosomes imparts the tumor with a granular appearance. They are most commonly observed in the oral cavity, skin and subcutaneous tissue, breast, and respiratory tract. Granular cell tumors rarely affect the gastrointestinal tract. We report a 58-year-old female with a past medical history of hypertension, mitral valve prolapse, and depression who presented for surveillance colonoscopy. A single firm sessile polypoid lesion, with overlying pale tan color mucosa, measuring approximately 1 to 1.5 cm, was found in the ascending colon. Biopsy of the nodule followed by histopathology was positive for S100 and CD68, but negative for AE1/AE3, CD117, smooth muscle actin, and desmin, consistent with the diagnosis of GCT. We review the clinicopathologic features of GCTs.