Measurement of lymph node function from the extraction of immunoglobulin in lymph

Background. We aimed to measure the extraction fraction of human immunoglobulin G (HIG) by the 1st echelon lymph node (sentinel node) following intradermal injection in patients with breast cancer undergoing axillary lymph node dissection (ALND) and examine its association with node size and presence and extent of nodal metastatic disease. Materials and methods. HIG labelled with either In-111 (n = 21) or Tc-99m (n = 9) was injected intradermally at the areolar. ALND was performed 2-4 h later. All lymph nodes were isolated and individually counted in a well-counter. The counts in the 'hottest' (1st echelon) node were expressed as a fraction of total counts in all the resected nodes. Since counts in the least hot nodes barely exceeded background, this fraction represents extraction fraction for the 1st echelon node. Presence of disease was noted in each 1st echelon node and the extent quantified as percentage replacement with disease. Results. Median extraction fraction in 1st echelon nodes with no or low (< 1%) disease burden (n = 21) was 68 (range 23-93)%, significantly higher (p < 0.05) than in diseased 1st echelon nodes (n = 9), in which it was 44 (21-66)%. There was, however, no association between extraction fraction in diseased nodes and disease extent. In nodes with no/low disease, extraction fraction was similar for the two radiolabels. There was no association between extraction fraction and node size. Conclusion. Nodal extraction fraction of HIG is a novel physiological measurement. It is reduced as a result of metastatic invasion. In the absence of disease, it shows no correlation with node size.