Cystic degeneration in phyllodes tumor. A source of error in cytologic interpretation

To examine problems encountered in the cytologic interpretation of phyllodes tumor (PT) with cystic degeneration and solutions thereof.

Cystic degeneration was found in seven PTs (five benign, one low grade and one high grade). Aspirates from these yielded fluid and were usually labelled fibrocystic change on the original cytology. Smears were retrospectively analyzed, with special attention to the background, presence and nature of the epithelial and stromal fragments, foam cells and naked nuclei in the background.

PTs with cystic degeneration on cytology showed thick fluid in the background, foamy macrophages (100%), apocrine cells (28%) and epithelial fragments, which showed nuclear atypia in two cases. On reviewing the smears, five of seven PTs had stromal fragments, albeit in small numbers. Most important, even in the absence of stromal fragments, all cases showed 5-50% naked nuclei of the fibroblastic type dispersed within the fluid background.

In cases of fluid aspirates from well-defined lumps, one must search for fibroblastlike naked nuclei or stromal fragments within the fluid to clinch the diagnosis of phyllodes tumor.