Background: Myofibroblastoma is a benign stromal tumor of the breast that occurs mainly in males. There are few reports on the cytologic aspects of breast myofibroblastoma, all of them corresponding to the classic type. Recently, some variants of myofibroblastoma were histologically described as: collagenized, epithelioid, cellular and infiltrant. Presently, the variant forms of myofibroblastoma have not been well characterized pathologically or clinically.
Case: A case of a cellular variant of myofibroblastoma was diagnosed by fine needle aspiration in a 68-year-old male. The aspirates consisted of highly cellular, cohesive groups of randomly arranged, plump oval and spindle cells. The nuclei had fine, uniformly distributed chromatin with inconspicuous nucleoli, and mild pleomorphism was observed. The cytoplasm was scant, with ill-defined borders. We did not observe epithelial components, inflammatory cells or collagenous stroma. Histologic examination showed a dense proliferation of interlacing, spindle-shaped neoplastic cells, with some nuclear atypia. Conspicuous collagen bands were present only focally in the tumor. The margins of the specimen were free, but the tumor had infiltrative borders microscopically. The spindle cells showed immunoreactivity for vimentin, desmin, muscle-specific action and CD 34.
Conclusion: Our case of a cellular variant of myofibroblastoma of the breast with expression of CD 34 adds more one benign spindle cell lesion of the breast that should be considered among the diagnostic possibilities for aspirates from this group of lesions.