A Rare Case of a Metastatic Malignant Abrikossoff Tumor.

Abrikossoff tumor, also called granular cell tumor (GCT), is a neoplasm of the soft tissues which is most commonly a solitary, painless, and benign tumor. However, 2% of Abrikossoff tumors can be malignant. We report here the case of a 75-year-old male who presented a local recurrence of Abrikossoff tumor of the left thigh. The anatomopathological analysis concluded to a malignant GCT, and the F-18 fluorodeoxyglucose positron emission tomography showed multiple lesions in the lymph nodes and bones. The potential conversion to malignancy should alert practitioners because of the extremely poor prognosis. The diagnosis of malignant granular cell tumor should be based on a bundle of clinical and histological features and not solely on histologic features because of the challenging distinction between malignant and benign tumors due to the lack of well-defined criteria for the diagnosis of malignancy. Large size and recurrence are the most important clinical features predicting malignant behavior. Patients with a history of Abrikossoff tumor should be followed closely to monitor recurrence and malignant transformation. The apparent originality of our observation - which could lie in the evolution of a GCT tumor, initially considered as benign, to a malignant form - has to be challenged regarding the issue of classifying some cases according to the classical "benign" and "malignant" dichotomy.