Granular cell tumor of the appendix: a new case and review of the literature.

Granular cell tumor (GCT) is a rare and usually benign lesion of neural / schwannian origin, most frequently found in middle-age women. The appendicular involvement is extremely rare: in over half a century only twelve cases have been reported in the literature, the patients living in America and Europe. Hitherto, no cases are documented from Africa, Asia and Oceania and no cases of malignant GCTs of the appendix have been reported. Most patients were diagnosed preoperatively as having acute appendicitis, whereas in three patients the tumor was incidentally detected during major abdominal surgery. The GCTs were equally distributed between mid-appendix and tip, where lymphoid tissue is more abundant and the anatomical nerve supply is progressively reduced. Moreover, the appendix surrounding the GCTs is characterized by the presence of chronic inflammatory cells (histiocytes, plasmocytes, eosinophils, mastocytes) and, therefore, a chronic inflammation of the appendix may be an antecedent condition favouring the appearance of GCTs. The GCT of the appendix appears so to be a lesion that reflects local reactive changes in the neural / schwannian cells, rather than being a genuine neoplasm. We describe the smallest GCT of the appendix ever reported, with a detailed literature review supporting its reactive origin in the lymphatic tissue-rich sites, such as ileo cecal appendix.