Abstract
The atypical spindle cell/pleomorphic lipomatous tumor (ASPLT) was classified as a new tumor by the World Health Organization (WHO) in 2020. The tumor is benign and commonly occurs in the limbs. Paraspinal presentations are rare. A 38-year-old man presented at our clinic complaining of sudden onset back pain. No neurological deficit was found. The magnetic resonance imaging (MRI) revealed a well-defined heterogeneous mass in the left psoas muscle, from L1 to L3 extending over the L1 and L2 neuroforamen. The tumor was totally excised. Pathology led to an ASPLT diagnosis. Clinical symptoms improved and there was no postsurgical neurological deficit. This case of ASPLT, located in an uncommon location and present an unusual cluster of symptoms, could be treated by surgical excision, usually the first-treatment strategy. Totally, removal was achieved because there was a clear morphological margin. The risk of metastatic dissemination was minimal, though there remains a nonnegligible risk of local recurrence.