220 Adenovirus Immunohistochemistry in Hematopoietic Stem Cell Transplant Patients Undergoing Gastrointestinal Biopsy

Abstract Introduction Adenovirus infection in patients who have undergone hematopoietic stem cell transplant (HSCT) is associated with significant morbidity related to respiratory, genitourinary, and gastrointestinal (GI) involvement, as well as disseminated disease and death. HSCT patients with GI symptoms often have endoscopy with GI biopsies for evaluation. The differential diagnosis in these specimens includes graft-vs-host disease (GVHD), infection, and medication-related changes. As these entities may have overlapping histologic features, and cytopathic changes with adenovirus are often subtle, immunohistochemistry (IHC) should be considered as part of the surgical pathologic evaluation. Detection of adenovirus is critically important in the HSCT population as infection may be fatal and can be treated using agents such as cidofovir. Methods GI specimens with adenovirus IHC performed from adult and pediatric HSCT patients from 2015 to 2016 at a single institution were reviewed to identify the frequency and pattern of positive cases. Results were compared with H&E-stained sections, concurrent studies for adenovirus, and clinical history. Results Four specimens (3.4%) with positive adenovirus IHC were identified from 117 GI cases for which adenovirus IHC was performed over the two-year period. Two specimens were from the duodenum and two from the colon. All cases had concurrent GVHD. Three cases had positive adenovirus PCR; of these, one also had positive adenovirus shell vial culture. The fourth case had positive stool adenovirus enzyme immunoassay and was also positive for adenovirus by viral culture of the GI specimens. Review of H&E-stained sections in IHC-positive areas of these four cases identified subtle viral cytopathic changes such as enlarged or smooth nuclei. Conclusions Adenovirus-infected cells can be rare and may show no or subtle viral cytopathic changes by standard H&E-stained preparation of GI biopsies. In HSCT patients, a low threshold for ordering immunohistochemical stains for adenovirus is warranted due to the clinical importance of this infection.