BACKGROUND: Mammary myofibroblastoma is a rare and benign neoplasm of the
breast stroma, showing features of fibroblasts and myofibroblasts. It has
also been noted to exhibit smooth muscle cell characteristics.
OBJECTIVE: The aim of this study was to describe the clinical and
pathological features of mammary myofibroblastoma reported at our
institution.
METHODS: Cases of mammary myofibroblastoma reported in our laboratory were
retrieved by electronic search. H&E slides were reviewed and
clinico-pathologic features were noted. Immunohistochemistery was performed
by Envision method. Only CD34 and CKAE1/AE3 were performed in all 6 cases.
ASMA, desmin and S-100 were performed in 5, 4 and 2 cases, respectively.
Vimentin and Bcl-2 were performed in one case.
RESULTS: A total of 6 cases were identified. Five were female and one was
male. The mean age of patients was 45.5 years. The mean size of tumors was
7.7 cm in the largest dimension. Histologically, four cases showed clusters
of uniform bipolar spindle shaped cells separated by broad bands of
hyalinized collagen. Mitotic figures ranged from none to 3 mitoses/10 HPFs.
One case showed combined features of cellular and fibrous areas. Another
case was epithelioid-cell type. On immunohistochemistry, CD34 stain was
positive in 5/6 cases, ASMA in 3/5 cases, desmin in 2/4 cases, S-100 in none
and vimentin and Bcl-2 in 1/6 cases. None of the cases stained positive for
CKAE1/AE3.
CONCLUSIONS: Due to the varying degree of fibro-myofibroblastic
differentiation, myofibroblastoma shows multiple morphologies and several
intratumoral and intertumoral types. It is essential to distinguish each
variant from the other to avoid inaccurate diagnosis of other benign or
malignant breast conditions, becoming a noteworthy diagnostic dilemma for
histopathologists.
