Atypical retiform hemangioendothelioma arising in a patient with Milroy disease: a case report and review of the literature.

Retiform hemangioendothelioma (RH) is a rare vascular neoplasm with a high rate of local recurrence and low metastatic potential. We describe an unusual case of RH in a 45-year-old patient with Milroy disease, with a prominent solid component diffusely involving a chronic lymphedematous leg. This case is consistent with the postulated relationship between lymphedema and vascular neoplasms developing as a result of local immune dysfunction, and highlights the need to closely monitor patients with Milroy disease for pathologic changes. Our case highlights a unique example of RH with atypical features. There are several noteworthy unusual clinical and histologic findings including diffuse involvement of an entire limb, solid component with cytologic atypia, D2-40 expression, and first-time-reported association with Milroy disease. Given the atypical histologic presentation of cytologic atypia, solid areas and atypical immunohistochemical profile with D2-40 positivity, this case could cause diagnostic difficulty, especially in the setting of such a broad clinical differential.