Tubular Cast Tutorial

There is a histopathologic spectrum to the casts that can be seen in light chain cast nephropathy. A portion of this spectrum is shown in these photomicrographs of renal biopsies stained with PAS. All three of these cases had casts with light chain restriction by immunofluorescence. Photomicrograph A shows the classic PAS-negative cast with a cellular reaction. The casts in Photomicrograph B have an elongated crystalline appearance. The casts in Photomicrograph C stain weak by PAS and have more of a granular appearance. It is important for the renal pathologist to be aware of this histopathologic spectrum though there is no known clinical significance to the variation in appearance by light microscopy.