Granular Cell Tumor at the Appendiceal Orifice: A Rare Case Treated With Right Hemicolectomy

Introduction: Granular cell tumor (GCT) is a rare mostly benign soft-tissue tumor that can occur anywhere in the body, with a mean age of diagnosis of 45 years. It is uncommon in the GI tract (8%), with the colon being an extremely uncommon location. There have been less than 100 cases of colonic granular cell tumor reported in the literature thus far. Here, we present a case of malignant GCT at the appendiceal orifice treated with right hemicolectomy. Case Description/Methods: A 37-year-old Hispanic woman underwent screening colonoscopy due to a history of colon cancer in a first-degree relative. The colonoscopy demonstrated a single erosion in the terminal ileum and a submucosal nodule at the appendiceal orifice. The nodule was resected and biopsy showed proliferation of round to ovoid eosinophilic cells with granular cytoplasm in the mucosa, submucosa and lamina propria that stained positive for S100. Patient underwent right hemicolectomy with the resection specimen showing a residual 2 mm focus of granular cell tumor with negative margins. There was no definitive morphologic evidence of malignant transformation and multiple additional sections were reviewed to confirm this. Reactive hyperplasia of mucosa-associated lymphoid tissue and focal acute ileitis with ulceration were also evident on tissue analysis (Figure 1). Discussion: Granular cell tumors (GCTs) are often found incidentally during colonoscopies and appear as yellowish-white nodules or polyps with normal overlying mucosa. Diagnosis is made through histopathology and Franburg-Smith criteria is used to differentiate benign from malignant GCTs. Although uncommon, malignant GCTs have a 40% mortality rate and a high recurrence risk. Small lesions (< 1cm) can be monitored, while larger lesions, especially those >4cm, have a significant malignant potential and require resection. Endoscopic removal is preferred and has been successful for lesions up to 2.6 cm.Figure 1.: A: GCT as a submucosal nodule on colonoscopy; B: Biopsy shows proliferation of round to ovoid cells with prominent eosinophilic, granular cytoplasm; C: Immunostaining shows the cells to be diffusely positive for S100.