Myxoid spindle cell lipoma of the ileum: Clinicopathological features and diagnostic insights.

Objective: This study analyzes a rare myxoid spindle cell lipoma (SCL) around the ileum. It aims to systematically summarize the clinicopathological features of this tumor at an atypical location. This will improve understanding of this rare condition. Material and Methods: We conducted a detailed study of SCL around the ileum. This mass was incidentally found in a right hemicolectomy specimen. The analysis integrated multiple methods. These included histomorphological observation, immunohistochemical staining, and molecular testing. Results: The tumor showed a typical myxoid stromal background. It contained spindle cells and scattered mature adipocytes. The characteristic thick collagen bundles commonly seen in classic SCL were absent. A diagnosis of myxoid SCL was confirmed based on the following features: CD34-positive spindle cells, loss of retinoblastoma protein 1expression, a low Ki-67 index, and the absence of MDM2 amplification by both IHC and fluorescence in situ hybridization. This profile effectively excludes malignant differential diagnoses, such as liposarcoma. Conclusion: Myxoid SCL around the ileum is extremely rare. Its diagnosis relies on recognizing its characteristic morphological spectrum. Immunohistochemistry and molecular testing are essential to exclude malignant tumors. A comprehensive understanding of its unique presentation at atypical sites is crucial. This is important for achieving accurate diagnosis and preventing inappropriate treatment.