Abstract

Immunohistochemical staining for cytokeratins can detect false negative nodes in patients with breast carcinoma. We report on a patient with breast carcinoma and pseudometastasis detected by immunohistochemical staining within a negative sentinel lymph node. A 66-year-old woman underwent a simple mastectomy and sentinel lymph node biopsy. Immunohistochemical staining of the sentinel nodes for cytokeratin in permanent sections showed cells with intense cytoplasmic staining in the subcapsular sinus. The cells were negative for epithelial membrane antigen staining, but positive for CD68. In combination with morphologic findings and immunohistochemistry, cytokeratin-positive cells were confirmed as histiocytes with phagocytized cytokeratin debris. Careful correlation with histology and additional IHC could help avoid a misinterpretation of this type of pseudometastasis.

• Keywords: Breast;Sentinel lymph node biopsy;Cytokeratin;Histiocytes;Pseudometastasis