Granular cell tumor is relatively rare soft tissue tumor that can present anywhere in the body. It commonly occurs in oral cavities and subcutaneous tissues, but is uncommon in the colon and rectum.[1, 2] This usually benign tumor appears as a submucosal nodule, measuring less than 2 cm in diameter, and is often found incidentally during colorectal examinations.[2, 3]

Case report

We report a healthy 52 years old African American patient who had a screening colonoscopy. He has a strong family history of colon cancer in his mother and two of his siblings. Colonoscopy revealed evidence of a 3 cm submucosal caecal mass that was not amenable to endoscopic resection due to subserosal involvement.

CT scan of abdomen and pelvis showed no evidence of any other associated mass or metastasis. The patient underwent a laparoscopic right hemicolectomy with robotic assistance. His postoperative course was uneventful and the patient was discharged home after three days. Histological examination of the resected mass revealed a poorly circumscribed collection of pale eosinophilic cells extensively infiltrating throughout the muscularis propria as well as focal areas of the submucosa. The cells varied in shape from round to spindled and had marked cytoplasmic granularity. The nuclei had varied appearances, ranging from small and dark to slightly larger and vesicular.No mitosis was noted. Periodic acid-Schiff staining accentuated the cytoplasmic granules (Figure 1). Immunohistochemistry demonstrated marked positivity with S-100 protein, CD68, and neuron-specific enolase and negativity with neurofilament (Figure 2). This was consistent with the characteristic staining profile of a granular cell tumor.

Discussion

The gastrointestinal tract is an unusual location for granular cell tumor.[4] In contrast to the present case, it usually involves submucosal area and measures less than two cm.[2,3] It is uncommonly detected in the muscle layer and in subserosal areas.[2, 5, 6] Granular cell tumor has a benign clinical course and an incidence of local recurrence in 5-10% cases after surgical resection.[1,7] It could seldom be diagnosed based on macroscopic and endoscopic examination due to both its small size and its shape resembling a diminutive polyp.[1]

People with two first-degree relatives who have, respectively, a colorectal cancer and a colonic adenoma should be offered screening colonoscopy every three to five years beginning at the age of 40.8 Granular cell tumor rarely gives rise to diagnostic problems because of its characteristic histologic picture.[4] These tumors seem to derive from Schwann cells, even if the earlier reports considered them to be of muscular origin.[9] Patients who are diagnosed with a granular cell tumor of uncertain malignant potential may benefit from preoperative radiologic evaluation because occult metastatic disease when identified, alters the surgical approach and possibly affect the long-term outcome.[10] The final diagnosis of granular cell tumor depends upon histo-pathological findings.[11]Since this tumor is considered to be usually benign, endoscopic removal has been recommended for management of colonic granular cell tumor[2,9,12,13] especially when endoscopic ultrasonography shows that the tumor is smaller than 2 cm and is well separated from the muscularis propria.[2,13,14] However, as in the present case, surgical resection should be considered for those cases in which endoscopic removal is not feasible and a limited surgical resection is indicated in order to obtain a clear diagnosis.9 In addition, surgical resection may become the treatment for a benign granular cell tumor because of the misinterpretation of the biopsied lesion.[15]

References