# Unmasking Hidden Clues in Cutaneous Viral Infections: Histopathological Insights Into Keratinocytic Features of Herpes Simplex Virus, Varicella Zoster Virus, and Molluscum Contagiosum

## TL;DR

This case study examines keratinocyte changes in skin viral infections to help pathologists diagnose cases with atypical features.

## Contribution

The study identifies novel histopathological clues in keratinocytes for diagnosing HSV, VZV, and MC when typical features are absent.

## Key findings

- 71% of HSV/VZV cases showed nucleolar enlargement and atypical keratinocytic features.
- MC cases consistently displayed a 'pregnant seahorse appearance' in keratinocytes around molluscum bodies.
- Immunohistochemistry showed positive staining in cytopathic cells but not in adjacent atypical keratinocytes.

## Abstract

Objective: This case study aimed to explore primarily the keratinocytic changes of cutaneous viral infections caused by herpes simplex virus (HSV), varicella-zoster virus (VZV), and molluscum contagiosum (MC). The focus was on identifying features and diagnostic clues in cases without typical findings.

Methods: A retrospective analysis encompassing 14 HSV/VZV cases (January 2000 to October 2023) and 22 MC cases (January 2013 to December 2015) was conducted.

Results: In HSV/VZV cases, 71% (10 of 14) exhibited distinctive histopathological features in the adjacent keratinocytes, including nucleolar enlargement and atypical features. Immunohistochemical studies in 40% of the cases (4 of 10) revealed positive staining in cells with cytopathic changes and negative staining in adjacent atypical keratinocytes. Conversely, MC cases consistently demonstrate an enlarged, stuffed "pregnant seahorse appearance" of keratinocytes around molluscum bodies.

Conclusion: This study highlights the diagnostic significance of keratinocytic changes in these viral infections, allowing pathologists to perform additional studies to make the correct diagnosis in cases where typical viral changes are not readily apparent.