Metaplastic carcinoma in an ectopic breast.

We describe the case of an 81-year-old woman in whom a mass developed in the chest wall over 3 weeks. No previous mass in that area was reported. Physical examination was remarkable only for a 13 cm painless, purplish mass in the anterior chest wall. No masses were palpable in the anatomic breasts, and no lymphadenopathy was evident. Thoracoabdominal computed tomography showed a 3.5 x 7.0 cm necrotic mass; underlying muscle invasion could not be excluded. Wide excision of the tumor and underlying fascia was done, and margins were clear. Pathology showed a metaplastic carcinoma without continuity with either anatomic breast. Adjuvant radiotherapy was initiated because of the tumor's high-grade features. Twenty-six months after resection and adjuvant treatment, the patient continues to be free of disease. Metaplastic carcinoma is an unusual pathologic finding in the anatomic breast. This is the first report of its occurrence in ectopic breast tissue.