Larotrectinib in a Patient With Advanced Pleomorphic Liposarcoma of the Uterus

Pleomorphic liposarcoma of the uterus (PLU) is an extremely rare disease with poor prognosis. Limited treatment options exist for these patients, and disease recurrence usually occurs rapidly within months of initial diagnosis. Few case reports of metastatic PLU are available in the literature. We describe a 70-year-old woman who presented with a large uterus and ovarian mass on imaging and negative serum tumor markers and endometrial biopsy. Staging revealed localized disease. Surgical resection revealed PLU on pathology. Immunohistochemistry was negative for smooth muscle actin (SMA), S100, and MDM2, and positive for CD10 and cyclin-D1. She was treated with adjuvant therapy and experienced disease recurrence in the liver at 15 months from surgery. Genetic testing of the metastasis showed IQGAP-NTRK3 gene fusion. She was given entrectinib but continued to show progression in the liver. Right partial hepatectomy was performed, showing positivity for CD10, BCL-1, MDM2, and SMA on tumor staining. Treatment was switched to pazopanib with disease progression in the neck. She was treated with larotrectinib last, showing no disease progression and adequate tolerance of therapy after 18 months of this treatment. This is the first case in the literature of metastatic PLU with NRTK3 fusion treated with sequential first-generation NRTK inhibitors. More case reports are needed to identify commonalities and therapeutic options. Genetic testing in all PLU cases is needed for targeted therapy approaches.