Sonographic appearance of a carcinoma developed in ectopic axillary breast tissue.

Primary breast cancer of ectopic axillary breast tissue is almost never diagnosed preoperatively. When not accompanied by nipple-areolar complex, the mass is often believed to be a lipoma, an enlarged lymph node, or a skin lesion such as a sebaceous cyst or hydradenitis suppurativa. When an axillary mass is found, a percutaneous needle biopsy is mandatory to rule out the diagnosis of cancer in ectopic breast tissue. We describe the sonographic findings of a case of ductal carcinoma in axillary ectopic breast tissue.