Cytological study of 20 cases of solid-papillary carcinoma of the breast.

Solid-papillary carcinoma (SPC) of the breast is a rare variant of low-grade intraductal carcinoma but there are few cytological studies. We examined 20 cases of SPC of the breast, aged 31-80 (mean age 66.0 yr), to define the cytological features. In each of the cytological specimens, we could find both malignant and benign cytological features; the former were characterized by hypercellularity, highly discohesive clusters, numerous isolated cells, and severe overcrowding cells, while the latter were marked by small and bland nuclei, a low nuclear-cytoplasmic ratio, and inconspicuous nucleoli. Neither abnormal naked nuclei of tumor cell origin nor oval naked nuclei of myoepithelial cell origin were seen. We also reviewed the cytological findings of SPC as well as neuroendocrine carcinomas with intraductal components that had been reported and we concluded that the coexistence of malignant and benign features was the most characteristic cytological feature of SPC.