Pazopanib For The Treatment of Malignant Granular Cell Tumors: Case Report and Review of The Literature

Granular Cell Tumors (GCT) represent 0.5% of all the Soft Tissue Sarcomas (STS), and when metastatic, they exhibit an aggressive behavior and limited survival. Metastatic GCTs are relatively chemoresistant; however, there is growing evidence on the benefit of using pazopanib and other target therapies in this histology. A literature review was performed for the available cases of malignant GCT treated with systemic therapies, excluding chemotherapy. Moreover, a patient with metastatic GCT treated with pazopanib in our center is reported here. Of the 254 articles found in our search, 9 articles met the inclusion criteria. Pazopanib was the most employed systemic therapy, accounting for 10 patients, including our case report. The mean reported time on therapy with pazopanib was 13.4 months. Nine of the patients experienced disease control with pazopanib and five patients achieved an objective response (Overall Response Rate: 62.5%). Molecular studies suggested that pazopanib antitumor effects may be due to a loss-of-function of ATP6AP1/2 genes which consequently enhance signaling trough several molecular pathways, such as SFKs, STAT5a/b and PDGFR-β. Other reported therapies for malignant GCTs included pazopanib in combination with crizotinib, which showed disease control for 4 months in one patient, and a PI3K inhibitor which achieved disease control for 9 months in another patient. Dasatinib and megestrol, were ineffective in two other different patients. Pazopanib demonstrates to be active in advanced GCTs and may be considered as a treatment option, based on the current available data founded on case reports.