Atypical fractured cast that is pale on PAS stain is suggestive of light chain cast nephropathy (LCCN). Immunofluorescence examination for kappa and lambda light chains is required for diagnosis. LCCN is most often due to a monoclonal kappa rather than lambda clone (~3:1) that is filtered by the glomeruli but accumulates in distal portions of the nephron.  In combination with Tamm-Horsfall protein, they are cytotoxic and obstructive.