Infiltrating lobular breast carcinoma: detection of occult regional lymph node metastasis by immunohistochemistry.

Twenty-two patients primarily operated for infiltrating lobular breast carcinoma (ILC) stage T2 with negative axillary lymph nodes in routine histology were investigated in order to detect occult metastasis in the nodes by immunohistochemistry. After testing a panel of monoclonal antibodies against cytokeratins, AE1/AE3 as the most sensitive marker for ILC cells was selected for the study. The immunohistochemical investigation of the 226 regional lymph nodes showed one case of a tumor cell embolus in the subcapsular sinus. Despite the fact that our routine examination included serial sections of the lymph nodes, an occult micrometastasis could be detected by immunohistochemistry only. As so far no significant prognostic value of micrometastasis to axillary lymph nodes of ILC has been shown, at the moment the clinical impact of the detection of micrometastasis is limited. Immunohistochemical methods do not appear to be an improvement for clinical decisions if careful histological examination of serial sections of lymph nodes in ILC is carried out.