Clinically, it presents as a palpable, hard, non-painful mass, often of a considerable inhibitor licensed size. It is often indistinguishable from a breast fibroadenoma (19, 20). It has never been associated with clinical signs of lymph node metastasis. Its appearance on mammography can vary considerably. In most cases, it appears as a large mass with relatively well-defined margins and lobulated edges, often containing focal or diffuse calcifications, that are generally coarse and dense (21�C23). However, cases with irregular margins are not uncommon. The presence of osteoid tissue in a breast tumor is not in itself indicative of osteosarcoma, as it may also be found in both benign and malignant epithelial or mesenchymal growths such as fibroadenoma, phyllodes tumor and metaplastic carcinoma.

However, scintigraphy will reveal an intense focal hotspot of the radionuclide 99mTc-diphosphonate, a specific marker for osteoid tissue, and therefore may strongly indicate a soft tissue bone cancer. It is thus useful in the instrumental diagnosis of breast osteosarcoma (24, 25). Given the low sensitivity of diagnostic tests, the exact identification of a primary breast sarcoma is possible only through histological examination, enabling the exclusion of osteogenic sarcoma deriving from the underlying bone structures (20). On immunohistochemistry, the tumor cells are generally positive on vimentin staining but negative for the epithelial markers MNF116 and CAM5.2 (cytokeratin), for the markers S-100, AE1/AE3, HER-2, desmin and actin and for progesterone and estrogen receptors (PGR and ER).

This is generally an aggressive tumor which often spreads through the circulation. For this reason, axillary dissection may not be indicated. Furthermore, due to the high risk of recurrence removal of the entire breast is recommended, with regular follow-up to enable early detection of any locoregional recurrences. Conclusion Rare tumors, while individually having a low incidence, collectively account for a considerable fraction of all breast tumors. ��Rare�� is used to describe tumors whose frequency ranges from 1 to 10%. These should be distinguished from unusual tumors, with a frequency of less than 1%, and exceptional tumors, of which there are only a few literature reports. Although these forms can be very complex, it should be stressed that rare does not mean incurable. On the whole, rare tumors are a major problem for both clinicians and, above all, pathologists, given the difficulty in forming a precise diagnosis GSK-3 from the possible classifications and the not uncommon impossibility of arriving at a clear prognosis. Pathologic classification is even more problematic in the exceptional cases in which two or more forms are found in the same breast.