# Atypical Spindle Cell Lipomatous Tumor: A Scoping Review of Current Insights Into Diagnosis, Pathogenesis, and Management

## TL;DR

This review explores the diagnosis and features of atypical spindle cell lipomatous tumors, highlighting the need for standardized protocols and updated understanding of their characteristics.

## Contribution

The study provides new insights into the diagnostic challenges and variable features of ASPLT, emphasizing the importance of Rb and MDM2 testing.

## Key findings

- CD34 was expressed in 90% of ASPLT cases, but desmin lacked diagnostic value.
- 44% of cases showed unexpected MDM2 positivity, suggesting overlap with ALT/WDL.
- ASPLT was found more frequently in axial locations like head, neck, and thoraco-lumbar regions.

## Abstract

Atypical spindle cell/pleomorphic lipomatous tumor (ASPLT) is a recently recognized benign adipocytic neoplasm, distinguished by specific histopathological and immunohistochemical features. Although traditionally classified as a tumor of the limbs and limb girdles, emerging evidence suggests a broader anatomic distribution. A systematic review of the literature was conducted using PubMed to identify ASPLT case reports published within the past decade. Cases were included if they had a confirmed ASPLT diagnosis, while reports describing unrelated neoplasms or limited by language barriers were excluded. Thirteen cases met the inclusion criteria. Data on patient demographics, tumor characteristics, immunohistochemical profiles, and diagnostic methodologies were extracted and analyzed.

CD34 expression was observed in 90% of cases, while desmin staining was inconsistently reported and lacked clear diagnostic value. Notably, 69% of cases omitted testing for Rb protein loss, a key marker in ASPLT classification. Unexpected MDM2 positivity was identified in 44% of tested cases, with one demonstrating gene amplification, suggesting potential overlap with atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL). Additionally, ASPLT occurred more frequently in axial locations than previously recognized, with eight cases located in the head, neck, and thoraco-lumbar regions. These findings emphasize the need for standardized diagnostic protocols, including routine Rb evaluation and MDM2 analysis, to ensure accurate classification. Future studies should explore the significance of MDM2 expression in ASPLT and reassess its anatomic predilection to refine diagnostic criteria and clinical management strategies.