Primary fibromatosis of the breast in a patient with multiple desmoid tumors--report of a case with evaluation of estrogen and progesterone receptors.

Fibromatosis (or desmoid tumor) is an infiltrative fibroblastic/myofibroblastic lesion presenting a moderate risk for local recurrence and no metastatic potential. Classically, these lesions are classified whether in abdominal or extra-abdominal sites, and may be multicentric or familial. Primary fibromatosis of the breast (PFB) is an uncommon lesion that shows histological similarities with abdominal fibromatosis (AF), and frequently poses difficulties in the differential diagnosis with other spindle cell tumors of the breast. It has been demonstrated that AF usually shows immunoreactivity for estrogen (ER) and progesterone (PR) receptors; conversely, in most of the studies, the cells from PFB are consistently negative for both receptors. We report on a case of a 41-year-old female with two desmoid tumors, affecting the abdominal wall and the breast tissue. To the best of our knowledge, there is no previous report in which hormonal receptors were evaluated in abdominal and mammary desmoid tumors in the same patient. We assessed the immunohistochemical expression of ER and PR in both lesions; while the AF showed immunoreactivity for both receptors, the cells from PFB were all negative. Although we have considered just this case, we still believe that these findings could support a distinctive etiopathogenesis of abdominal and mammary fibromatosis.