Metaplastic carcinoma of the breast-A rare neoplasm with transitional cell differentiation: An exceptional feature.

Metaplastic carcinomas of the breast are malignant breast neoplasms composed of a mixture of both epithelial and mesenchymal elements. The rarity of this tumor is exemplified by the fact that it accounts for only about 0.2% of all breast carcinomas. It can present histologically with diverse differentiation and the exact histogenesis of these tumors is unknown. The present case is reported for its rarity and for the presence of transitional cell differentiation along with the other usual components of metaplastic carcinoma. Transitional cell differentiation in a metaplastic carcinoma has not been documented in the literature. Besides this, it highlights the importance of special stains and immunohistochemistry in evaluating these carcinomas and the need for early diagnosis and excision of these tumors as these carcinomas generally have a poorer prognosis as compared to breast carcinomas without metaplasia, with the tumor size having an important bearing on the outcome of this condition.