Metastatic Granular Cell Tumor: A Rare Entity

Granular cell tumor, which is thought to recapitulate a Schwann cell phenotype, is a very rare neoplasm that belongs to soft tissue tumors. It can be classified as benign, atypical or malignant, based on specific histological criteria, with the majority of cases exhibiting an indolent behavior. Its biology and clinical course are poorly understood and its optimal management is yet to be defined, given the rarity of cases. Here we describe an atypical granular cell tumor in the upper middle back skin that evolved after a thirty-year indolent period. Despite complete surgical removal, the patient experienced a recurrence, both local and in the lungs, following an aggressive clinical course. Data on management of metastatic disease are extremely scarce, comprised exclusively of case reports. Therefore, we administered to the patient systemic therapy according to soft tissue sarcoma guidelines, which led to disease progression, with fatal outcome. In conclusion, recurrent and/or metastatic granular cell tumor is a rare disease that can be life-threatening, for which response to different therapies is unknown. The biologic behavior of atypical and malignant granular cell tumor is quite different from its benign counterpart, evoking soft tissue sarcomas, and its diagnosis should alert clinicians. The role of adjuvant chemotherapy and radiation therapy in this setting should be explored, to limit disease recurrence.