# Stage IV SMARCA4‐Deficient Undifferentiated Malignant Neoplasm With Primary Cutaneous Origin and Early Distant Metastases

## TL;DR

This paper reports a rare case of a skin cancer called SD-UMN that was already advanced at diagnosis and spread to other parts of the body.

## Contribution

The paper presents a new case of primary cutaneous SD-UMN with early distant metastases, expanding the clinical understanding of this rare cancer.

## Key findings

- The patient was diagnosed with Stage IV SD-UMN upon presentation, with metastases to lymph nodes and liver.
- This case adds to the limited knowledge of SD-UMN's clinical and histopathological features.
- The case emphasizes the need to distinguish SD-UMN from other similar skin cancers due to its aggressive behavior.

## Abstract

SMARCA4‐deficient undifferentiated malignant neoplasms (SD‐UMNs) are a recently recognized group of malignant epithelioid tumors, associated with mutations in the SWItch/Sucrose nonfermentable chromatin remodeling complex. To our knowledge, there have been only three cases of SD‐UMNs primary to the skin. We report a rare case of primary cutaneous SD‐UMN in an 85‐year‐old male with a former 25‐pack‐year smoking history. Unlike previous cases, he notably was diagnosed as Stage IV upon presentation, with metastatic involvement of lymph nodes and liver. Our case highlights the importance of recognizing SD‐UMN from other types of poorly differentiated cutaneous epithelioid malignant neoplasms, given its aggressive nature and potential for targeted therapies. It also adds to the growing but still limited understanding of the clinical and histopathological features of this rare malignancy.