The immunohistochemical profile of granular cell (Abrikossoff) tumor suggests an endomesenchymal origin

Granular cell tumor (GCT) is an uncommon soft tissue neoplasm which has an unclear histogenesis. The aim of this study was to analyze its immunophenotype and hypothesize on the histogenesis of GCT. A database of 2,250 soft tissue tumors was examined to identify and characterize the particularities of GCTs. A large panel of antibodies was used. Of the 2,250 tumors, only 15 were GCTs (0.66 %); these were diagnosed in patients whose average age was 37 years. Among them, 5 had malignant potential, the remaining 10 were benign. One of these benign tumors was associated with a metachronous chondrosarcoma with metastases in the lungs. No recurrences were reported in these cases. The benign tumors displayed positivity for S-100, neuron-specific enolase (NSE), CD56, epithelial membrane antigen (EMA), and inhibin. In the atypical GCTs, NSE, S-100 protein, c-KIT, RET and EMA were positive, while inhibin and CD56 were negative; rare osteoclastic-like histiocytes, marked by CD68, were seen. All cases were negative for CD31, CD34, smooth muscle actin, desmin, maspin, and calretinin. Ovoid bodies expressed CD105, synaptophysin, and HER-2. All the cases were microsatellite-stable tumors. The immunoprofile suggests that the GCT seems to have an endomesenchymal origin. The c-KIT and RET positivity, associated with microsatellite stability, and the immunoprofile of the ovoid bodies have never reported before in GCTs.