Osteosarcoma arising in the breast.

We report on a 49-year-old woman with osteosarcoma arising in the breast. She had undergone two consecutive excision biopsies for right breast tumors at ages 40 and 42 years. The tumors were diagnosed as a fibroadenoma and a benign phyllodes tumor, respectively. At age 46 years, she noticed a gradually enlarging mass in the same breast. After 3 years, at age 49 years, total mastectomy was performed. The tumor occupied the entire breast and measured 12x9x8.5 cm. The tumor cells were spindle-shaped and pleomorphic, with large, irregular nuclei and distinct nucleoli. Many tumor cells had characteristics of osteoblastic and chondroblastic elements producing osteoid, osseous, and cartilaginous intracellular substances. Pathologic mitoses and apoptotic cells were frequent. Neoplastic cells had infiltrated the skin. Blood and lymph vessel invasion was present. Tumor cells expressed vimentin, osteopontin, vascular endothelial growth factor, CD10, and alkaline phosphatase, but did not express keratin. Chemotherapy was not effective. The patient died of multiple pulmonary metastases 9 months after mastectomy.

Primary breast mucosa-associated lymphoid tissue (MALT) lymphoma with high-grade transformation evidenced by prominent lymphoepithelial lesions.

Primary breast lymphoma, particularly primary mucosa-associated lymphoid tissue (MALT) lymphoma, is a rare disease. We report here a case of a MALT lymphoma of the breast with high-grade transformation. An 84-year-old woman presented with a Pagetoid mass in her right breast. After a clinical diagnosis of breast cancer, T2N1M0, stage II B, she underwent mastectomy with axillary lymph node dissection. She had no history of autoimmune disease such as Hashimoto thyroiditis or Sjögren disease. Pathologically the tumor tissue was composed of small to large lymphoid cells. The large cells contained a considerable number of centroblasts, forming a sheet-like proliferation centrally. Among the small cells many small cleaved cells were present, which were more predominant in the peripheral areas. Immunohistochemistry revealed that these cells were positive for CD20 and CD79a. The tumor cells infiltrated the ductular epithelial cells, distorting the duct structures, to form lymphoepithelial lesions. Immunohistochemistry for cytokeratin and CD20 was helpful for identification. No germinal centers were formed. MALT lymphoma with high-grade transformation was diagnosed. Rituximab (anti-CD20 antibody) was prescribed as systemic treatment without chemotherapy or irradiation. After 18 months, no tumor recurrence was observed. We emphasize the importance of lymphoepithelial lesions for the diagnosis of MALT lymphoma of the breast.