Argyrophil carcinoma of the breast: a cytologic, histochemical, and ultrastructural study of a case.

Aspirate from an argyrophil carcinoma ("carcinoid") of the breast showed malignant dispersed epithelial cells. With Diff-Quik, the cytoplasm was seen to be abundant, with prominent eosinophilic granularity. The nuclei were fairly uniform, round or oval, and eccentric and had a finely stippled chromatin pattern. On histology, the tumor appeared typical for argyrophil carcinoma, and staining with Grimelius for argyrophilic granules was positive. Membrane-bound neurosecretory granules were seen on electron microscopy.