“Giants in a Microcosm”

On examination of a breast mass surgically excised in a 69-years-old woman, a pure invasive micropapillary carcinoma (MPC) was diagnosed (Figure 1). At close examination, intensely eosinophilic syncytial-multinucleated giant cells (CD68+) percolating the stromal bands were identified (Figure 1). The breast carcinoma illustrated here shows therefore a combination of 2 rarities, namely, an invasive micropapillary growth pattern and an osteoclast-like giant cell (OGC) component. The World Health Organization blue book classifies the “carcinoma with osteoclast-like stromal giant cells” among rare variants of invasive carcinomas of no special type (IC-NSTs)1; however, OGCs can also accompany a variety of breast cancer special types (cribriform, tubular, mucinous, papillary, lobular, squamous and other metaplastic patterns1,2). Identification of giant cells populating MPCs can be challenging as they feature the same size as the micropapillae and only differ in staining (more eosinophilic cytoplasm) (Figure 1).