Fine needle aspiration biopsy of primary breast myxofibrosarcoma: a case report.

Background: Primary soft tissue sarcomas of the breast are extremely rare neoplasms, and the value of a fine needle aspiration biopsy (FNAB) in the preoperative or intraoperative diagnosis of soft tissue tumors in the breast is still controversial. Nevertheless, correct recognition of such lesions can avoid unnecessary sentinel and axillary lymph node dissection.

Case: We report a 45-year-old woman who presented with a 10-cm tumor in her right breast. FNAB showed spindle-shaped cells with nuclear pleomorphism, occasional intranuclear cytoplasmic inclusions, myxoid stroma and curvilinear vessels. Immunocytochemical staining for cytokeratins was negative. A diagnosis of a primary myxoid breast sarcoma was made, and the possibility of a myxofibrosarcoma vs. malignant phyllodes tumor was suggested. A right mastectomy was performed, and a primary myxofibrosarcoma of the breast was confirmed by histologic examination.

Conclusion: The key cytologic features of myxofibrosarcoma are spindle cell proliferation with a moderate degree of nuclear pleomorphism, myxoid stroma and curvilinear blood vessels. Although cytologic features of myxofibrosarcoma are not entirely specific, supplementary negative immunocytochemistry for different molecular weight cytokeratins indicates a soft tissue neoplasm.