Bilateral infiltrating lobular carcinoma of the breast with osteoclast-like giant cells.

A case of bilateral infiltrating lobular carcinoma of the breast containing osteoclast-like giant cells is presented. Notable pathologic features include prominent tumor-associated angiogenesis and the presence of osteoclast-like giant cells in axillary lymph node metastases. Immunohistologic and ultrastructural examination support a nonepithelial, histiocytic origin for the giant cells, and results are similar to previous reports of osteoclast-like giant cells associated with breast carcinoma. This is the first report of bilateral pure infiltrating lobular carcinoma of the breast with osteoclast-like giant cells and the first case of pure lobular carcinoma with osteoclast-like giant cells present in lymph node metastases.