Imaging Findings of Atypical Spindle Cell/Pleomorphic Lipomatous Tumors: A Case Series and Systematic Review

This study aimed to examine the CT and MRI features of atypical spindle cell/pleomorphic lipomatous tumors (ASCPLTs) through a case series and systematic review. A literature search was conducted using MEDLINE and Scopus databases, covering the period from January 1, 2017, to June 9, 2025. The following keywords were used: ("atypical spindle cell lipomatous tumor") OR ("atypical pleomorphic lipomatous tumor") OR ("atypical spindle cell/pleomorphic lipomatous tumor"). The study included five patients from our institution with histopathologically and immunohistochemically confirmed ASCPLTs, along with 18 additional cases identified from 18 published articles. Imaging findings were reviewed retrospectively. A total of 23 patients with ASCPLTs were analyzed (14 male patients and nine female patients; median age, 60 years; age range, 13-87 years). The median lesion size was 115 mm. Fourteen lesions (61%) were superficial, and nine (39%) were deep. Tumor margins appeared well-defined in 20 (87%) cases and ill-defined in three (13%) cases. A capsule was identified on T2-weighted images in 9/12 (75%) cases. Fatty and non-fatty components were observed in 14/18 (78%) and 15/18 (83%) cases, respectively, with non-fatty components predominating in 13/18 (72%) cases. Imaging patterns were classified as follows: atypical lipomatous tumors in 3/17 (18%) cases, spindle cell lipoma in 3/17 (18%), myxoid liposarcoma in 5/17 (30%), dedifferentiated liposarcoma in 4/17 (22%), and undifferentiated pleomorphic sarcoma in 2/17 (12%). Key imaging characteristics of ASCPLTs included large size (>100 mm), superficial location, well-defined margins, presence of a capsule, and predominance of non-fatty components. While ASCPLTs frequently contained fat, their imaging presentations varied widely.