- To review and illustrate imaging findings of common and uncommon lesions that may mimic malignant mesenchymal tumors. - To review imaging features that should warrant further investigation.

Pseudosarcomas are one of the most important pitfalls in soft-tissue pathology. They are a vast group of nonneoplastic lesions that can be mistaken for malignant mesenchymal tumors. Ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) have a key role in the initial evaluation. An interdisciplinary approach with pathology and correlation with clinical history is also often necessary for a definitive diagnosis.

In this work, we present a pictorial review of lesions mimicking soft-tissue malignant tumors and review imaging findings that may help guiding the differential diagnosis, using relevant examples of the daily practice in our institution. Soft-tissue Pseudosarcomas are benignsoft-tissue lesionsthat canbe mistaken formalignancies and should be in the differential diagnosis whenconsidering asarcomatous etiology–. Someofthese entities have acharacteristic appearence or location that the radiologist must be aware of.– They mayhaveaneoplastic (e.g.myxoma)ornon-neoplastic origin(e.g. hematomas). Soft-tissue tumors arise–from the mesenchyme,which differentiates tobecome fat,skeletal muscle,peripheral nerves,blood vessels and fibrous...

–It is important for the radiologist to be familiar with soft-tissue pathologies that may mimic malignant mesenchymaltumors like thepseudosarcomasof this work. They are a diagnostic challenge but should be in consideration in differential diagnosis, although in many cases only the pathology study will reveal the correct diagnosis.

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Gisela Andrade, Radiology resident (3rd year) [email protected]