# Sequential Dermoscopic, Histopathologic, and Immunopathologic Documentation of Regressing Seborrheic Keratosis: A Multimodal, Time‐Resolved Visual Case Study

## TL;DR

This case study documents the rare spontaneous regression of a seborrheic keratosis over 8 weeks using multiple imaging and analysis techniques.

## Contribution

The study provides the first fully time-resolved clinicodermoscopic-immunopathologic sequence of cytotoxic regression in seborrheic keratosis.

## Key findings

- Sequential imaging showed structural changes in seborrheic keratosis during regression.
- Immunohistochemistry revealed CD8+/TIA-1+ cytotoxic T-cell activation and keratinocyte apoptosis.
- Keratinocyte-derived amyloid deposition was observed during the regression process.

## Abstract

Seborrheic keratosis (SK) typically shows stable behavior, and spontaneous regression is rarely documented. We report a unique case of SK that underwent complete involution within 8 weeks. Sequential clinical and dermoscopic imaging demonstrated a transition from classical SK structures to red‐blue homogeneous areas and, ultimately, to whitish regression zones. Histopathology revealed interface inflammation, keratinocyte degeneration, and epidermal remodeling. Immunohistochemistry confirmed a stepwise regression mechanism involving CD8+/TIA‐1+ cytotoxic T‐cell activation, cleaved caspase‐3–mediated apoptosis, and keratinocyte‐derived amyloid deposition. To our knowledge, this is the first case to demonstrate a fully time‐resolved clinicodermoscopic‐immunopathologic sequence of cytotoxic regression in SK.

Seborrheic keratosis may undergo rapid spontaneous regression driven by cytotoxic T‐cell activation. Sequential dermoscopy and immunopathology revealed a stepwise process involving keratinocyte apoptosis and keratinocyte‐derived amyloid deposition.