Malignant Tenosynovial Giant Cell Tumor of the Foot

Abstract

Malignant tenosynovial giant cell tumors (T-GCT) or malignant pigmented villonodular synovitis (PVNS) is extremely rare, accounting for less than 50 reported cases worldwide [1–3]. Enzinger et al. first described malignant TGCT as uncontrolled growth within a benign lesion or as the recurrence of a previously benign lesion [4]. The feature characteristics that suggest malignancy are nodular and/or solid infiltrative growth pattern, large round or oval cells, cells with large nuclei and nucleoli, areas of necrosis, and atypical mitoses [3, 5]. Histology diagnostic criteria for malignant TGCT by the Armed Forces Institute of Pathology (AFIP), including five out of eight characteristics, are (1) diffuse pleomorphism, (2) prominent nucleoli, (3) high cytoplasmic to nuclear ratios, (4) mitotic ratio greater than 10 per 10 HPFs, (5) necrosis, (6) discohesion of tumor cells, (7) paucity of giant cells, and (8) diffuse growth pattern [6]. Molecular characteristics of malignant T-GCT involve deregulated CFS1 overexpression, aberrations of cyclin A, P53, and chromosome arm 15q [7]. Malignant T-GCT is a highly aggressive tumor with potential for local destruction, distant metastases to the regional lymph nodes and lung, and death from disease. Despite aggressive management, including surgical resection, chemotherapy, and radiation, studies showed a median survival of 22.5 months after diagnosis [2, 3]. A limited number of limb-salvage procedures have been reported for malignant T-GCT following wide resection.