[Clinicopathological characteristics of pulmonary artery intimal sarcoma]

Objective: To describe the clinicopathological features of pulmonary artery intimal sarcoma (PAIS), and to understand its molecular alterations. Methods: Sixty cases of pulmonary artery endarterectomy performed at the China-Japan Friendship Hospital, Beijing, China from January 2017 to January 2020 were reviewed. Clinical data of 5 patients with pulmonary artery intimal sarcoma were collected. Hematoxylin-eosin staining, immunohistochemistry staining and fluorescence in situ hybridization (FISH) were performed to evaluate the pathological features. RNA sequencing was conducted to assess the fusion gene changes in PAIS. Results: The detection rate of PAIS was 8.3% (5/60), with the median age of 49 years and a female predominance. Their clinical manifestations were non-specific. Histopathological examination showed that the tumors were composed of malignant spindle or epithelioid cells, with various degrees of atypia. Focal heterologous osteosarcomatous or leiomyosarcomatous differentiation was noted. The tumor cells could express PDGFRA, CDK4 and MDM2 with co-amplification of MDM2, CDK4 and EGFR genes. RNA sequencing detected multiple in-frame fusions in the tumors. Conclusions: PAIS is a rare, highly heterogeneous, and poorly-or un-differentiated sarcoma accompanied by complex changes of multiple genes.It has no known effective treatments, and thus has a poor prognosis.