Granular Cell Tumor of Rectum: A Very Rare Entity

Abstract

Granular cell tumor (GCT), also called as Abrikossoff tumor is a rare neoplastic process which is mostly benign. Granular cell tumors can develop in any part of the body, though oral cavity and subcutaneous tissue are the most common sites. Only about 10% of the tumors develop in the gastrointestinal tract with esophagus being the most common site and rectum being the rarest. We here present one such rare case of rectal granular cell tumor. A 61-year-old man with medical comorbidities of coronary artery disease, congestive heart failure, hypertension, dyslipidemia presented to the GI clinic for screening colonoscopy. The patient denied any gastrointestinal related complaints. Screening colonoscopy revealed good bowel preparation with a score of 8 on Boston Bowel Preparation Scale, a 1cm serrated adenomatous polyp in the transverse colon that was removed with hot snare polypectomy and a firm 4mm nodule in the rectum that was removed with biopsy forceps (Figure - 1). Biopsy of the rectal nodule revealed a granular cell tumor with positive periodic acid-Schiff (PAS) staining (Figure - 2). Immunohistochemical staining for S100 protein was positive as well (Figure - 3). A subsequent rectal endoscopic ultrasound (EUS) confirmed complete removal of the tumor. Granular cell tumors (GCTs) are mostly benign and very rarely malignant with tumors >4cm in size having metastatic potential. Patients with GCTs are mostly asymptomatic and GCTs are usually incidental findings. However, large tumors are known to present with hematochezia and/or pain. GCTs are more common in women than in men. Patients with GCTs are usually between the 4th and the 6th decades of life. The tumor can present as a painless, non-ulcerated nodule or a yellowish-gray sessile polyp with firm consistency. Endoscopic ultrasound can be used to evaluate the tumor invasion into the wall of the gastrointestinal tract. Diagnosis is made with histology. Fanburg-Smith et al. proposed six histological criteria to differentiate benign tumors from malignant ones. The six criteria include- cellular necrosis, pleomorphism, increased nuclear-cytoplasmic ratio, enlarged nucleoli, increased mitotic activity and cell elongation. A tumor is considered malignant if 3 or more criteria are fulfilled. Benign tumor can be removed with endoscopic resection as was the case with our patient. Surgical resection should be reserved for large and multifocal tumors.Figure 1Figure 2Figure 3