[Primary pulmonary epithelioid hemangioendothelioma: a clinicopathological analysis of 40 cases]

Objective: To investigate the clinicopathological features of primary pulmonary epithelioid hemangioendothelioma (PEHE). Method: Forty cases of PEHE were diagnosed from October 2010 to June 2024 at the First Affiliated Hospital of Zhengzhou University, Zhengzhou, China. A retrospective analysis was conducted on their histological features, imaging findings, immunohistochemical characteristics and molecular phenotypes. Subsequently, the clinicopathological features were summarized. The patients were followed up. Result: Of the 40 cases, there were 19 males and 21 females, age 52.5 (43.0, 62.0) years old. Most patients were admitted for respiratory symptoms, mainly cough (25/40) and expectoration (14/40). Computed tomography findings mainly showed multiple intrapulmonary nodules (33/40) and solitary nodules in 7 cases (7/40). Tumor maximum diameters ranged from 3 to 70 mm, with a median of 19 (12, 35) mm. Grossly, all lesions appeared as grayish-white nodules with ill-defined margins and mucoid cut surfaces. Microscopically, tumor cells showed centrifugal distribution around blood vessels, arranged in irregular nests; local mucoid degeneration and chondroid matrix were noted. Intracytoplasmic vacuoles with red blood cells were noted in some tumor cells, indicating primitive vascular lumen differentiation. At the molecular level, WWTR1-CAMTA1 gene fusion was identified in 36 cases and YAP1-TFE3 fusion in 4 cases. Immunohistochemical results showed diffuse positivity for CD31 (38/38), CD34 (36/40), ERG (40/40) and Fli-1 (40/40), and focal positivity for TFE-3 (4/34). Therapeutic responses of 40 patients were assessed using the Response Evaluation Criteria in Solid Tumors criteria: complete response in 4 cases (10.0%), partial response in 5 (12.5%), stable disease in 7 (17.5%), and progressive disease in 24 (60.0%). Conclusions: PEHE is a rare vascular-derived tumor, radiologically characterized by multiple bilateral pulmonary nodules. It has non-specific clinical manifestations; combined use of highly sensitive and specific endothelial markers and genetic testing helps reach the definitive diagnosis. PEHE has an overall indolent course, with long-term survival in some patients. However, multiple lesions, pleural invasion, and distant metastasis may be linked to worse prognoses.