Answer: Angiosarcoma

Histology: Adjacent to the biopsy cavity, there is a proliferation of spindle cells lining well formed interanastomosing vascular channels and infiltrating the breast parenchyma and fat. The cells show mild to moderate atypia and rare mitotic activity. No solid areas or areas of necrosis are identified. There is no evidence of invasive or in situ breast carcinoma.

Discussion: The lesion represents a well to moderately differentiated angiosarcoma (AS) of the breast. Although overall it is a rare lesion 44% of AS occur in the breast. AS of the breast can be divided into two categories primary and secondary, the latter mostly related to radiation therapy. Primary angiosarcoma typically occurs in premenopausal women. The majority present as a painless mass of variable size. Microscopically, the lesion is composed of interanastomosing channels. Grade usually correlates with prognosis with high grade lesions occurring in young women and having a bad prognosis. Low grade lesions show minimal atypia and rare to absent mitosis, with no evidence of tufting or solid areas. At the other end of the spectrum high grade AS show papillary formations, endothelial tufting, solid areas, necrosis and high mitotic activity. The differential diagnosis of low grade lesions includes hemangioma, PASH or a hematoma mainly when diagnosed on needle core biopsy. High grade AS should be differentiated from metaplastic carcinoma. It is noteworthy that up to 35% of AS stain for keratin in the epithelioid areas and 2% of metaplastic carcinomas stain for CD31 and CD34 but the presence of a conventional invasive carcinoma component or DCIS helps in the diagnosis. Low grade primary AS can progress to high grade. Metastases can occur to lymph nodes (6-8%), the contralateral breast (21%), to bone, lungs, liver, brain, ovary and skin. Almost 70% of the patients are dead of disease.

Secondary AS occurs in 2 clinical settings, lymphoedema post mastectomy and more commonly post radiation therapy. The occurrence of AS is not related to the dose of radiation and it occurs 6 months to more than 15 years following radiation. In contrast to primary AS, secondary AS occurs in post menopausal women and arises in the dermis (not the breast parenchyma). Morphologically it is similar to secondary AS. It is a locally aggressive disease with multiple local recurrences even in cases treated with complete surgical excision. Metastases occur after frequent recurrences and the most common site of recurrence in these cases is the contralateral breast.

Reference(s):
– “Vascular proliferations of the breast”. C Brodie & E Provenzano, Histopathology 2008,52:30-44.