Malignant Diffuse Tenosynovial Giant Cell Tumor: Case Report and Review of the Literature

Abstract

Diffuse-type tenosynovial giant cell tumor (TGCT) is a neoplasm that exhibits infiltrative growth, tends to recur locally, and is often located within a joint. We describe a challenging diagnosis and clinical course of a 14-year-old girl with malignant diffuse TGCT, highlighting the difficulty of acquiring a representative biopsy. The patient presented with a painful foot mass, which was diagnosed initially through open biopsy as chronic osteomyelitis. Because her pain persisted, additional open biopsies were performed 1 and 2.5 years after the initial biopsy, which also showed features of benign TGCT. At age 16 years, she underwent marginal resection but developed local recurrence with metastatic disease 1 year later. Core needle biopsy of the foot mass again confirmed diffuse TGCT and showed no evidence of atypical or malignant features. Malignant features were confirmed only through excisional biopsy of chest wall metastasis. The patient started chemotherapy and underwent below-the-knee amputation at age 17 years. Amputation specimen showed malignant diffuse TGCT. She died of disease progression approximately 1 year later. Metastasis of diffuse TGCT with benign histology is challenging to diagnose. Previous studies have also found that benign diffuse TGCT can transform into an aggressive, malignant tumor. This case highlights that biopsy sampling can be challenging in histologically heterogeneous tumors. Initial evaluation by a multidisciplinary team, as well as image-guided biopsy techniques, may increase diagnostic accuracy of the biopsy.