Concomitant primary angiosarcoma and invasive carcinoma of the breast: a case report.

Collision tumor is a rare entity composed of two different tumors that occur in close to one another and maintain distinct borders. Only few cases have been reported in the breast. We report the first case of concomitant and adjacent primary angiosarcoma (PBAS) and invasive carcinoma of the breast (IBC), in a 45-year-old patient which presented with a lump in her right breast. Biopsy revealed PBAS. She underwent mastectomy. Gross examination showed a hemorrhagic and spongy tumor in contact with a second small grayish-white mass. Histologically, the hemorrhagic tumor was consistent with a high grade (HG) PBAS; the second mass was consistent with an IBC with no images of histological admixture. The diagnosis of a collision tumor composed of HG PBAS and IBC was established. During follow-up, the patient developed ovarian angiosarcomatous metastasis. The diagnosis of breast collision tumor is very uncommon and hence is challenging for pathologist. Careful gross and microscopic examinations help in establishing the appropriate diagnosis.