[A rare autopsy involving primary squamous cell carcinoma of the breast showing a very rapid and aggressive clinical course].

A rare autopsy case of a primary squamous cell carcinoma of the breast is reported. A 74-year-old Japanese woman, suffering from a left axillary nodule, underwent a radical mastectomy in May, 1986. The histopathological diagnosis had revealed a primary squamous cell carcinoma of the breast with a small area that indicated a solid tubular carcinoma. The patient, however, died four months later after a very rapid and aggressive metastasis of the tumor cells to her various organs. The autopsy revealed the presence of metastatic tumor cells in the systemic organs including the heart, lungs, liver, spleen, kidneys, pancreas, the bone marrow, and in the whole gastrointestinal tract. Histopathologically, the metastatic tumor cells in these organs were composed of squamous cell carcinoma solely, without tubular formation, showing a remarkable keratinization and mitotic activity. The histogenesis and the nature of the squamous cell carcinoma of the breast are briefly discussed.