Two cases of solid papillary carcinoma of the breast were pathologically studied. Subjects included two female patients: a 76-year-old (Case 1) and a 43-year-old (Case 2). Both cases showed solid and papillary proliferation of spindle cells in expanded ducts, perivascular pseudorosettes, eosinophilic fine granules in an abundant cytoplasm, intracellular mucin production, and positivity for chromogranin A. Case 1 showed an aggregation form involving multiple ducts, admixture of signet-ring like cells, mucin pools, and small and large electron-dense granules and flocculent granules in electron microscopy. Case 2 showed a solitary and compact form in a dilated duct and an interlacing bundle pattern.