[A case of lobular carcinoma of the breast containing endocrine granules]

A case of lobular carcinoma containing many endocrine granules in the breast of a 76-year-old woman is reported. Histologically, tumor cells proliferated in solid or nest-like patterns featuring lobular carcinoma. Although argyrophilic and immunohistochemical reactions for peptide hormones were negative, electron microscopic observation revealed endocrine granules, 200-400 nm in diameter, associated with a limiting membrane and a halo in every tumor cell examined. It was suggested that this case might be considered a variant of lobular carcinoma and that breast cancer showing lobular patterns should be searched for the possibility of endocrine differentiation.