Related Experiment Video
Updated: Jun 21, 2026
Identifying, Diagnosing, and Grading Malignant Peripheral Nerve Sheath Tumors in Genetically Engineered Mouse Models
Published on: May 17, 2024
Muscle fibers inside a fat tumor: a non-specific imaging finding of benignancy
M Donato1, D Vanel, M Alberghini
1Department of Anatomical Pathology Hospital Dr. R.A Calderón Guardia, Universidad De Costa Rica, P.O. Box 6098-1000, San José, Costa Rica.
Introduction:
The differential diagnosis between benign and low-grade well-differentiated malignant lipomatous tumors might be very difficult for both the radiologist and the pathologist, although it has practical consequences. Among the criteria, muscular fibers detected inside the lesion are considered radiologically and histologically as a reliable sign of a benign intramuscular lipoma. New genetic criteria are now available. We report two cases of fat tumors containing muscular fibers both radiologically and histologically, but which are definitely malignant, considering genetic criteria.
Material And Methods:
Two cases of soft tissue fat tumors, containing muscular fibers on imaging examinations as well as histologically, had an aggressive behaviour, suggesting malignancy. Genetic criteria were therefore used to confirm the clinical impression.
Results:
MDM2 and CDK4 confirmed the malignancy in the two cases.
Conclusion:
Intra lesional muscular fibers detected on imaging or histological examinations should not be considered as a completely reliable sign of a benign intramuscular lipoma. In case of atypical clinical behaviour, genetic criteria should be used to prove the aggressiveness of the tumor.
Related Concept Videos
01:48Classification of Skeletal Muscle Fibers
Slow-Twitch Muscle Fibers
Slow oxidative, muscle fibers appear red due to large numbers of capillaries and high levels of...
01:13Microscopic Anatomy of Skeletal Muscles
The muscle sarcolemma is a plasma membrane enclosing each muscle cell that conducts electrical signals called action potentials. The sarcolemma extends into the cell to form T-tubules, ensuring the neural impulses are uniformly distributed across the entire muscle...