Abdomen Malignant Myxoid Leiomyosarcoma with PDGFRA and TP53 Missense Mutation: A Case Report

Background: Malignant myxoid leiomyosarcoma (MMLS) is most commonly found in the uterus but can also occur in other areas, such as the extremities, vulva, chest wall, and abdominal cavity. This cancer is more prevalent in women and has a poor prognosis with a high rate of recurrence and a significant percentage of metastasis. Case Representation: Herein, we report the case of a 64-year-old female patient who presented with 3-month history of left lower abdominal mass. The patient underwent abdominal malignancy resection and was subsequently diagnosed with myxoid leiomyosarcoma. The patient experienced a recurrence and metastasis with significant ascites after the initial surgery and did not respond to treatment with oral Anrotinib in combination with Tislelizumab immunotherapy. Further genetic testing using next-generation sequencing (NGS) identified missense mutations in the PDGFRA and TP53 genes in the patient's plasma, but no mutations in the KIT gene were detected. Immunohistochemical analysis of the tumor tissue also revealed a negative expression of PD-L1. As a result, we altered her targeted therapy to Avapritinib, which resulted in significant improvement in her symptoms, including abdominal distension and pain, a decrease in ascites, and the KPS score increased from 60 points before treatment to 90 points after treatment SD (stable disease) was achieved for three months after treatment. Conclusion: In this case report, we present the instance of a patient with malignant myxoid leiomyosarcoma with a missense mutation in both the PDGFRA and TP53 genes. We found that targeted therapy with Avapritinib was effective in achieving a positive outcome in this patient. Our findings suggest that genetic detection is possible to better understand the biological behavior, genetic characteristics, and patient's response and tolerance to certain drugs, thus selecting the best treatment plan for the patient. Avapritinib may be a promising new treatment option for leiomyosarcoma patients with similar genetic mutations.