The Significance of So-Called Equivocal Immunohistochemical Staining for Cytomegalovirus in Colorectal Biopsies

Apoptosis, Crypt Dropout, and Equivocal Immunohistochemical Staining May Indicate Cytomegalovirus Infection in Inflammatory Bowel Disease Patients

Cytomegalovirus (CMV) colitis superimposed on inflammatory bowel disease (IBD) can be challenging to diagnose. This study aimed to determine what histologic clues and immunohistochemistry (IHC) utilization practices, if any, can help diagnose CMV superinfection in IBD. Colon biopsies were reviewed from all patients with CMV colitis with and without IBD between 2010 and 2021 at one institution, along with a separate cohort of IBD patients with negative CMV IHC. Biopsies were assessed for histologic features of activity and chronicity, phlebitis, fibrin thrombi, basal crypt apoptosis, CMV viral cytopathic effect (VCE), and CMV IHC positivity. Features between groups were compared, with statistical significance set at P-value <0.05. The study included 251 biopsies from 143 cases (21 CMV-only, 44 CMV+IBD, 78 IBD-only). Compared with the IBD-only group, the CMV+IBD group was more likely to show apoptotic bodies (83% vs. 64%, P=0.035) and crypt dropout (75% vs. 55%, P=0.045). CMV was detected by IHC in 18 CMV+IBD cases without VCE on hematoxylin and eosin (41%). In the 23 CMV+IBD cases where IHC was performed on all concurrent biopsies, IHC was positive in at least 1 biopsy in 22 cases. Six individual CMV+IBD biopsies with no VCE on hematoxylin and eosin demonstrated equivocal IHC staining. Of these, 5 had evidence of CMV infection. IBD patients with superimposed CMV infection are more likely to demonstrate apoptotic bodies and crypt dropout compared with their noninfected counterparts. Equivocal IHC staining for CMV may indicate true infection in IBD patients, and staining multiple biopsies from the same accession can improve CMV detection.

The Trends of Immunohistochemistry for Tissue-Invasive Cytomegalovirus in Gastrointestinal Mucosal Biopsies: A Large Single Academic Center Study

CONTEXT.—

Cytomegalovirus (CMV) immunohistochemistry (IHC) is the most widely used method to diagnose CMV infection/reactivation in tissues in a pathology laboratory.

OBJECTIVE.—

To improve the efficiency of CMV IHC testing by evaluating immunopositive staining trends of tissue-invasive CMV in the gastrointestinal system.

DESIGN.—

A total of 1479 individual orders for CMV IHC on gastrointestinal biopsy specimens from 2016 to 2018 were included. The analysis was performed to identify the significant factors contributory to CMV-positive test results.

RESULTS.—

The overall positivity rate of CMV IHC in our institution is 4.73% (70 of 1479). The positivity rate from physician-requested and pathologist-initiated tests was significantly different (7.54% versus 3.83%, P = .004). Cases with severe inflammation showed a higher positive CMV rate than those with mild inflammation (5.37% versus 2.60%, P = .04). Cytomegalovirus positivity in biopsies from posttransplant patients, inflammatory bowel disease, human immunodeficiency virus (HIV)/common variable immunodeficiency (CVID), cancer, and others was 19.69%, 3.84%, 23.33%, 9.00%, and 2.84%, respectively. The positivity rate among posttransplant, HIV/CVID, or cancer patients was significantly higher than in other populations. Cases tested with multiple tissue blocks generated a higher positivity rate than those with a single block (7.77% versus 3.23%, P < .001). Testing 3 to 4 blocks per case almost tripled the positive CMV detection rate (9.04%). Interestingly, using 5 or more blocks did not further ameliorate the positive CMV detection rate.

CONCLUSIONS.—

The data revealed that physician request, immunosuppression, multiple blocks, and severe inflammation were strongly related to positive CMV IHC detection rate. These findings might provide value in helping pathologists manage CMV IHC testing more efficiently.

Infectious diseases of the upper gastrointestinal tract

A broad spectrum of pathogens produce gastrointestinal disease. The ongoing spread of human immunodeficiency virus/acquired immune deficiency syndrome, the increased use of immunosuppressive therapy and the persistence of overcrowding and suboptimal sanitation in underdeveloped areas facilitate both disease transmission from environmental and foodborne sources and person-to-person transmission. Clinicians increasingly rely on endoscopic biopsy sample interpretation to diagnose gastrointestinal infections. Thus, pathologists must be aware of diagnostic features of a variety of microbial pathogens. Detection with molecular techniques also allows for correlation between infectious agents and their histopathological features, which has expanded our knowledge of the inflammatory changes produced by infectious agents. This review covers infectious disorders of the upper gastrointestinal tract encountered in surgical pathology. Clinical, endoscopic and pathological features are presented. The review emphasises morphological features of viruses, bacteria, fungi and parasites that may be found in tissue samples, and the inflammatory patterns that they produce. Differential diagnoses and useful ancillary techniques are discussed.