Hyaline globules in mammary myofibroblastoma: a case report.

A 52-year-old otherwise healthy woman presented with a solitary firm mass in the right breast. Histopathological evaluation of the 1.5-cm mass showed a mammary myofibroblastoma of the conventional spindle-cell type. High-power examination of hematoxylin-eosin-stained sections showed round, eosinophilic, intracytoplasmic, as well as extracellular, hyaline globules. These 5- to 20-µm globules appeared gray with a pinkish rim on Masson's trichrome stain. Immunohistochemically, the hyaline globules were strongly reactive with smooth muscle myosin heavy chain, desmin, and caldesmon. Histologically similar inclusion bodies have been reported in phylloides tumors--including those with myoid differentiation. To our knowledge, this is the first description of hyaline globules, a peculiar histological curiosity with no known clinical significance, in mammary myofibroblastoma.