Spindle cell and cartilaginous metaplasia in a breast carcinoma with osteoclastlike stromal cells. A difficult fine needle aspiration diagnosis.

The cytologic picture in fine needle aspirates from a unique type of breast tumor, with stromal proliferation of osteoclastlike giant cells, cartilaginous metaplasia and metaplastic spindle-shaped carcinomatous cells, is described. In this case, an erroneous cytologic diagnosis of fat necrosis associated with a rich component of reactive fibroblasts was made. This false-negative report, which was mainly due to lack of an obvious carcinomatous component in the aspirated material, is discussed with emphasis placed on the need to exclude spindle cell metaplasia in a breast carcinoma whose aspirates are characterized by a rich component of spindle-shaped cells.