Tip-148;
Myofibroblastoma is a purely mesenchymal, benign tumor of the mammary stroma, that presents as a slow-growing, painless, non-tender mass, in older patients. It is composed of fibroblasts and myofibroblasts consisting of bland, oval to spindle cells with pale to eosinophilic cytoplasm, arranged haphazardly or in short intersecting fascicles with interspersed variably hyalinized collagen bundles. It can exhibit storiform or even a neuronal-like appearance. The nuclei are bland-looking although focal pleomorphism is described. The tumor does not show features of malignancy including the lack of infiltrative growth pattern, high-mitosis, or necrosis. By immunostaining, the tumor cells typically show co-expression of CD34 and desmin. Other immunostains like STAT-6, Cytokeratins, and EMA are negative.
It occurs most commonly in the breast parenchyma. Still, it can also occur in extramammary sites, the so-called mammary-type myofibroblastoma, especially in the inguinal/groin area, vulva, perineum, and scrotum.