Cytological study of 44 cases with solid papillary carcinoma and a systemic review of solid papillary carcinoma and neuroendocrine tumor of the breast.

BACKGROUND: Solid-papillary carcinoma (SPC) of the breast is a rare variant of low-grade in situ and invasive carcinoma but there are only a few of the cytologic studies. METHODS: We examined 44 cases of SPC of the breast to define the cytologic features. We also made a systemic review of reported cases of SPC and neuroendocrine tumor (NET) of the breast. RESULTS: Both of our and the reviewed cases with SPC were very similar in the cytologic finding. It included hypercellularity, highly discohesive clusters, numerous isolated cells, small nuclei, finely granular chromatin of salt-and-pepper appearance, inconspicuous nucleoli, low nuclear-cytoplasmic ratio, and a plasmacytoid appearance. Moreover, SPC and NET had frequently all of these features in common. Capillary vessels structures and mucinous substance were not frequently seen in our and the reviewed cases with SPC. Rosette and pseudorosette were very rare in the cytologic specimen. The immunocytochemistry with our 9 cases with SPC indicated diffuse positivity for chromogranin A and/or synaptophysin. CONCLUSION: Many cytologic features are frequently shared by SPC and NET of the breast. However, the vascular structure may not be a precise criterion for SPC. Rosette and pseudorosette are rarely helpful for the cytologic diagnosis.