Detection of occult tumor cells (OTC) and micrometastases (MM) in axillary lymph node by microscopic ultrastaging

Purpose: Early breast cancer presents with a remarkable heterogeneity of outcomes. Undetected, microscopic lymph node tumor deposits may account for a significant fraction of this prognostic diversity. About 10% of nodal negative patients may represent OTC/MM in axillary nodes (Querlozi et al. 2006). So, axillary nodes were investigated immunohistochemically. OTC were defined as tumor cell deposits within the nodes measuring <0.2mm and MM measuring >0.2mm, but <0.2cm (Hermanek et al. 1999).

Methods: On routine workup, three step sections were performed for each node. Consecutively, 359 LN's from 68 nodal negative BC at different tumor stage and histology were examined using two commercially available pan-cytokeratine antibodies (MNF 116 and AE 1/3; dilution 1:100). Antigen retrieval was performed by cooking with traget retrieval solution (DakoCytomation) for 20min for each antibody at pH 9.0 for MNF 116 and at pH 6.0 for AE 1/3.

Results: Six out of the examined nodes showed OTCD (=1.7%) and occurred in five out of 68 (7.3%) BC studied. The median size of the OTC was 906.7µm (range: 60–1.480µm). MM were not observed.

Conclusions: Despite of the use of step sectioning in routine workup of axillary nodes in BC, immunohistochemical ultrastaging is capable to detect OTC in about 7%, but the rate of the detection of MM is not improved. The prognostic significance of OTC is questionable at time.