144 Clinical epidemiology of Masson tumor

Intravascular papillary endothelial hyperplasia (IPEH), also known as Masson tumor–a rare, benign vascular lesion typically presenting in the skin a subcutaneous nodule – may be clinically mistaken for other neoplasms such hemangiomas and lipomas. IPEH is classically categorized into three types:1) pure type arising dilated endovascular spaces; 2) mixed developing from preexisting abnormalities; 3) extravascular type. While prognosis of excellent, it must differentiated malignant tumors angiosarcomas, which require intensive treatments. Because literature on limited, we sought to characterize clinical pathological features IPEH. Subjects were identified using Mass General Brigham (MGB) Research Patient Data Registry included individuals with pathologically proven diagnosis 1/1980 8/2021 at Massachusetts Hospital, Women’s Hospital (BWH), BWH Faulkner Hospital. Demographic information, documentation, pathology reports reviewed data extraction. 261 diagnosed IPEH, majority being women (60%) white (74%). The average age was 53 years old [4-98 old]. most frequently involved anatomic sites upper (29%) lower (24%) extremities. Common initial diagnoses lesions cysts, hemangiomas, subtype common (50%), followed by (46%) subtypes (4%). Extravascular occurred more (5%) compared men (1%). We found that clinicians’ impressions prior biopsy did not include final -- often vague terms “soft tissue mass” indicating potential need greater awareness this condition. Given differential includes conditions melanoma or angiosarcoma, clinicopathologic correlation utmost importance uncommon lesion.