Masson's tumor of the reconstructed breast.

Intravascular papillary endothelial hyperplasia (Masson's Tumor) is a rare benign endothelial vascular lesion that can mimic angiosarcoma if not properly recognized. It represents less than 2% of all vascular tumors, but has been seen in the postradiation setting, which also makes differentiating it from angiosarcoma crucial. It is classically characterized as a circumscribed, intravascular mass that is hypoechoic on ultrasound, and T1 isointense and T2 heterogenous on MRI with variable enhancement. Histologically, it demonstrates papillary architecture without significant atypia, and associated vascular thrombus. Although it typically occurs in the soft tissues of the trunk and neck, a very small percentage of cases have been found in the breast. The following case will involve a 64-year-old female with a Masson's tumor involving the capsule of her left breast implant, in the setting of previously treated ductal carcinoma in situ, which was surgically excised and irradiated over 20 years prior.