Lost in preservation: failure of kappa and lambda detection by in situ hybridization in kidney biopsy specimens fixed in Michel transport medium

Abstract Context: In situ hybridization (ISH) for kappa and lambda immunoglobulin light chains is an important ancillary tool for identifying monoclonal plasma cell or B-cell infiltrates in kidney biopsies. We observed that kidney biopsy cores transported in Michel transport medium (MTM) showed markedly diminished or absent kappa and lambda ISH signals compared with their formalin-fixed counterparts. Objective: To evaluate the effect of MTM fixation on kappa and lambda ISH signal intensity in ki