Primary Epithelioid Angiosarcoma of the Breast: A Rare and Challenging Biopsy Diagnosis.

BACKGROUND Primary angiosarcoma of the breast is a rare neoplasm, accounting for less than 0.04% of all breast cancers. Epithelioid angiosarcoma is even more unusual with only a handful of cases reported in literature. Differentiating this from other breast malignancy is a challenge. There have been conflicting reports regarding factors that affect prognosis. We present a case of primary epithelioid angiosarcoma of the breast, and also discuss the prognostic and differential diagnostic issues. CASE REPORT A 70-year old female presented with slowly enlarging fungating mass in the right breast with a necrotic center and serosanguineous discharge. Initial biopsy done at an outside institution reported the lesion as carcinosarcoma. Histologic sections showed cellular, infiltrative neoplasm with extensive necrosis and ectatic vascular proliferations lined by plump endothelial cells. Infiltrative cells were spindle-shaped with vacuolated cytoplasm and marked anisonucleosis in myxoid background. Mitotic activity was brisk. CAM5.2, AE1/AE3, and CD31 were positive. Proliferation index was high. Estrogen receptors (ER), progesterone receptors (PR), human epidermal growth factor receptor 2 (HER2)/neu were negative. CONCLUSIONS Primary epithelioid angiosarcoma of the breast can present as a diagnostic dilemma in needle biopsies. This malignancy may mimic carcinoma or benign endothelial lesions. This entity is important to be recognized because it carries poor prognostic risk and requires distinct treatment modalities different from the usual epithelial breast neoplasms.