A Case of Colonic Granular Cell Tumor Treated by EMR 339 Table 1. Granular cell tumors occurring in the colon and rectum, as reported in the English literature Ac, ascending colon; Tc, transverse colon; Sc, sigmoid colon; Dc, descending colon; FOBT, fecal occult blood test; EMR, endoscopic mucosal resection. Author (Ref No.) Age/sex Year 1991 1992 1995 1996 2000 2000 2000 2001 2003 2003 2003 2003 2004 2006 2006 Current case Choi (8) Joshi (5) Yamada (9) Kulaylat (2) Nakachi (10) Rossi (11) Kim (12) Irisawa (13) Endo (14) Kim (15) Lee (16) Ryu (17) Sohn Mori Park 39/F 52/F 62/M 49/F 47/F 38/M 40/M 64/F 56/M 36/F 49/M 40/F 48/M 55/M 41/M Location Ac Tc Ac Ac Rectum Cecum Appendix Ac Sc Ac Ac Ac Tc Cecum Cecum Dc may be located anywhere between the rectum and the cecum, with a preferential location in the ascending colon and cecum based on the results of our literature review (Table 1). How- ever, the most common locations for colorectal GCTs are the rectum and cecum in the literature including approximate- ly 100 cases of colorectal GCTs (6, 11, 21). Colorectal GCTs occurred multiply in 10 to 20% of all reported cases (5, 22). Endoscopic findings of colorectal GCTs are yellow or yel- low-white submucosal nodules covered by normal mucosa or sessile polyps, or less frequently, pedunculated polyps (1- 3, 13). Thus, colonoscopists should generally consider the possibility of a GCT in the differential diagnosis of a yellow- ish submucosal tumor of the colon. Nonetheless, Palazzo et al. (23) reported that the correct diagnosis of GCT is seldom made based on macroscopic and endoscopic examinations, even if a diagnosis is made based on the results of endoscop- ic biopsy, and that these techniques yield a definite diagnosis in only 50% of all patients with GCTs. In some cases, endo- scopic biopsy finding was misinterpreted as an other diagno- sis (10). To obtain a definite diagnosis of a submucosal tumor by endoscopic biopsy, it is necessary to sample such tumors either by boring or by performing a jumbo biopsy, and/or if feasible, by carrying out a polypectomy or a mucosal resec- tion. Actually, 12 (75%) of 16 patients with colonic GCTs in our analysis were diagnosed by polypectomy or EMR. Endoscopic ultrasonography has recently been applied for evaluating gastrointestinal submucosal tumors, but it may not sufficiently distinguish a benign submucosal tumor, such as a GCT, from malignant neoplasia, such as a carcinoid (10, 14). However, it can contribute to planning the endoscopic resection by determining the depth of tumor invasion (23). Histologically, a GCT is composed of a nested growth com- prising large tumor cells with ample granular cytoplasm and small round nuclei. The histological findings consist of plump Symptoms Loose stool None Rectal bleeding Abdominal pain None None None, anal fistula None FOBT positive None Constipation Abdominal pain None None None None Size (mm) 9×8 25×15 5×3 4 8 10 7 15×10 6 15×6 7 15×15 4 9×6 15×12 12 Therapy Polypectomy Surgery Polypectomy Polypectomy Surgery Surgery Polypectomy Surgery EMR Polypectomy Polypectomy Polypectomy Polypectomy Polypectomy Polypectomy EMR neoplastic cells with abundant granular eosinophilic cyto- plasm containing acidophilic, p-aminosalicylic-acid-positive, diastase-resistant granules; small, uniform nuclei in which mitotic figures are absent; and neural markers, including S- 100 proteins or neuron-specific enolase. Granules either arise from autophagocytosis of the cell membrane or represent derivatives of the Golgi apparatus (24). The histological fea- tures of GCTs are uniformly expressed and should be ade- quate to establish the diagnosis (1, 6-9, 19). In our patient, the endoscopic and histological findings of the resected speci- men were indeed compatible with GCT. Few data exist, however, regarding the malignant potential and thus the appropriate management of colonic GCT. No evidence of malignant GCT in our reviewed 16 patients were noted. Johnston et al. (6) also found no evidence of malignant GCT in 78 cases of GCTs in the gastrointestinal tract and perianal lesions. Nonetheless, a malignant variety of GCT has been reported (25, 26). The malignant GCT seems to be correlated with the size of the tumor since most malignant forms are larger than 4 cm. Rapid growth and invasion of adjacent tissue as well as large size were reported to be more indicative of malignant behavior than the histological fea- tures. Other reported features associated with malignancy include cell necrosis, spindling of tumor cells, cytologic aty- pia and high mitotic activity, vescicular nuclei with large nucleoli, a high nuclear-to-cytoplasm ratio, and high expres- sion of p53 and Ki-67 (25-27). In our patient, any evidence of malignancy was not seen in the resected tumor. It is usually accepted that endoscopic resection is the best treatment for colonic GCTs, since colonic GCTs are consid- ered to be usually benign. Actually, 12 (75%) of 16 patients in our analysis and 26 (79%) of 33 patients in other report (14) were successfully treated with polypectomy or EMR without complications. Although there are no guidelines for