Mesenchymal tumors and tumor-like lesions of the breast: a contemporary approach review.

The classification of the breast tumors has been revised and recently published in 2012 in the WHO blue book. Contrary to the epithelial tumors in the breast, mesenchymal tumors are rare and the classification for benign and malignant tumors is based on the same criteria in both categories, since no other specific diagnostic criteria, which would have an impact on prognosis, exist to date. The present review deals with minor changes mirroring the recent developments in the benign mesenchymal tumors (new additions are nodular fasciitis and atypical vascular lesions, while the haemangiopericytoma is removed) focusing especially on criteria to diagnose sarcomas, which represent a wide spectrum including very difficult lesions. The majority of sarcomas of the breast arise as a component of a malignant phyllodes tumor, while the pure forms are very rare. When a pure primary sarcoma of the breast is diagnosed, pathologists are encouraged to categorize the lesion according to the type of differentiation and to provide to the clinicians all the important prognostic parameters for the best treatment choice.