Inflammatory myofibroblastic tumor of the breast.

Three patients developed firm, mobile, nontender masses in their breasts. Two were discovered by the patients and one after mammography. Macroscopically, the nodules were firm, circumscribed, yellow on cut sections, and composed of interlacing cytologically bland spindle cells admixed with chronic inflammatory cells, the latter predominantly of lymphocytes and plasma cells. Immunohistochemistry yielded strong smooth-muscle actin reactivity within the spindle cells; 2 lesions were negative for pankeratin, 1 was focally and weakly positive. No lesions were positive for anaplastic lymphoma kinase-1, desmin, S-100, CD34, CD21, or CD35. In each case, a diagnosis of inflammatory myofibroblastic tumor was made (aka, inflammatory pseudotumor). After conservative excision with apparently negative margins, there have been no recurrences, except in one patient who developed a recurrence after 3 months. The latter recurrence was managed successfully with a second excision. We report these patients to emphasize the diagnostic features of inflammatory myofibroblastic tumor of the breast and discuss how they can be distinguished from other spindle-cell breast lesions with which they can be confused, especially spindle-cell carcinoma.