Extramammary Myofibroblastoma in the Axilla of a Male Patient: A Case Report and Literature Review
Keywords:
myofibroblastoma, extramammary, spindle cell, desmin, estrogen receptor (ER), Bcl-2Abstract
Mammary type myofibroblastoma in an extramammary location is an extremely rare benign lesion. The site involved is usually along the embryonic milk line with the inguinal/groin region as a common location. Here we report a case of such lesion in an old man who presented with a painless mass in the right axilla. Histologically the lesion was comprised of loosely distributed bland spindle cells in a pseudoangiomatous background. No cellular atypia or mitosis was identified. Immunohistochemistry showed the spindle cells were immunoreactive to CD34, ER, and Bcl-2, but negative for desmin, cytokeratin, S-100, CD99, PR, CD21, and CD23. Ki-67 proliferative index for the spindle cells are very low. A diagnosis of extramammary myofibroblastoma was rendered after multiple extramural expert consultations. The uniqueness of this case includes: 1) pseudo-angiomatous and loose stroma background with on obvious interspersed collagen bundles; 2) negative for desmin, which is usually positive for this type of tumor; and 3) positive for Bcl-2, which has never been reported. Comparison of this entity with spindle cell lipoma at genetic level and a literature review were also conducted.
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