Utility of Microtubule Associated Protein-2 (MAP-2) Immunohistochemistry for Identification of Ganglion Cells in Paraffin-Embedded Rectal Suction Biopsies

Abstract

Identification of rare ganglion cells in rectal suction biopsies can be difficult for surgical pathologists who only occasionally encounter rectal suction biopsies for the diagnosis of Hirschsprung disease. We evaluated the utility of a monoclonal antibody directed against microtubule associated protein-2 (MAP-2), a marker of neuronal differentiation, to detect ganglion cells in formalin-fixed, paraffin-embedded tissue sections. The presence of ganglion cells was evaluated retrospectively by immunohistochemical staining for MAP-2 in 78 biopsies from 56 patients with ganglion cells present on hematoxylin and eosin (H&E) stain and 91 biopsies from 46 patients with no ganglion cells present on H&E stain. A total of 78 biopsies from 49 patients diagnosed as equivocal or suboptimal for ganglion cells on H&E stain were also examined. MAP-2 antibody clearly highlighted ganglion cell bodies in all 78 biopsies with ganglion cells present on H&E stain, including immature forms, and was negative in 88 biopsies with no ganglion cells present on H&E stain. In 3 biopsies from 2 patients with no ganglion cells present on H&E stain, MAP-2 antibody highlighted rare ganglion cells and in each case, the patient was confirmed not to have Hirschsprung disease on follow-up biopsy. MAP-2 immunoreactive cells were also identified in 14 biopsies from 12 patients diagnosed as equivocal for identification of ganglion cells on H&E stain. Three of these patients were found not to have Hirschsprung disease on repeat rectal suction biopsy and 6 additional patients in this group showed no evidence of Hirschsprung disease by clinical follow-up. This study indicates that MAP-2 antibody is a sensitive and specific immunohistochemical marker that can confirm ganglion cells in paraffin-embedded rectal suction biopsies and may eliminate the need for repeat biopsy in select cases.