Ultrastructural and immunohistochemical features of lobular carcinoma of the breast

Abstract

Twenty cases of infiltrating lobular carcinoma (12 of classical type, five of trabecular type and three of alveolar type) and one case of lobular carcinoma in situ were studied by transmission electron microscopy. The in situ component in three of the infiltrating carcinomas was also studied. The ultrastructure of the tumour cells in the alveolar variant of infiltrating lobular carcinoma was the same as seen in the tumour cells of lobular carcinoma in situ. The tumour cells in infiltrating lobular carcinoma of the classical and trabecular types had more irregular nuclei and were more organelle- and filament-rich. Immunohistochemical staining for the presence of α-lactalbumin, casein, prekeratin and carcinoembryonic antigen (CEA) was done. The presence of α-lactalbumin was proved in 19 per cent of the cases, casein 81 per cent, CEA in 65 per cent and prekeratin in 90 per cent. The light microscopic separation of some subgroups of infiltrating lobular carcinoma may be difficult, in particular the distinction between the classical and the trabecular variants. Unfortunately, our study shows that these distinctions cannot easily be made either by electron microscopy or by light microscopic immunohistochemistry with antibodies against prekeratin, CEA, casein and α-lactalbumin.