Objectives: Gastrointestinal infections by cytomegalovirus (CMV) and adenovirus may complicate hematopoietic stem cell transplantation (HSCT). Although CMV and adenovirus produce recognizable cytopathic changes, these changes may be subtle or focal. The value of viral immunohistochemistry in detecting infection in HSCT recipients when cytopathic changes are not identified has not been demonstrated.
Methods: H&E-stained sections from gastrointestinal biopsy specimens were reviewed by three pathologists. Cases were classified as negative, suspicious, or positive for CMV and/or adenovirus infection based on the presence or absence of viral inclusions. Viral immunohistochemistry was performed, and the results were compared with the interpretations of H&E-stained sections.
Results: Four of 104 cases contained viral inclusions confirmed by immunohistochemistry: two were infected with CMV, and two were positive for adenovirus. All three reviewers correctly classified both immunopositive CMV cases on H&E evaluation. However, all reviewers missed the diagnosis of adenovirus on H&E assessment in one case.
Conclusions: In HSCT recipients, cytopathic changes of adenovirus may be easily missed in H&E-stained sections of gastrointestinal biopsy specimens. Thus, the routine use of adenovirus immunohistochemistry in all cases is recommended. Both cases of CMV infection were apparent on H&E evaluation, so the judicious use of immunohistochemical stains for CMV in selected cases may be considered.