PNET of the psoas

Case contributed by Dr Ian Bickle


30 year old female. Fall and hospital admission 7 weeks prior. MRI suggested intra-muscular haematoma. Readmitted with ongoing pain and swelling in the left flank. Haemoglobin drop of 1 unit. Psoas haematoma re-bleed?

Patient Data

Age: 30 years
Gender: Female

Initial presentation

High T2 and T1 mildly hyerintense signal in an expanded left fibers iliacus, psoas and iliopsoas muscles.

Edema in the adductor longus, obturator externus, tensor fascia lata muscle as well as medial part of the hamstrings and lateral part of the gluteal muscles. Similar appearances of the sartorius and quadratus femoris muscle as well as in the anterior abdominal wall muscles on the left side.

There is extensive edema with dilated lymphatics involving the subcutaneous fat in the upper thigh and lower abdomen.

A few mildly enlarged nodes in the groin .

Visible hip joint appears normal.

No bony abnormality.


7 weeks later.

Large well defined high atteunation mass in the left psoas/iliopsoas extending caudally lateral to the femoral artery into the muscle groups of the medial aspect of the thigh.

This abuts the acetabulum, but without cortical irregularity.

The bladder and uterus are displaced medially.

A few reactive left groin nodes.

Upper abdomen normal.

Comment: Left iliopsoas mass. This may well represent an organized hematoma, however in view of this being evident for more than a month without resolution and the manner in which it extends into the upper thigh an alternative diagnosis such as a sarcoma merits thought.

It is amenable to ultrasound guided biopsy should this wish to be considered.


Ultrasound guided biopsy performed.

The percutaneous biopsy specimen report for the psoas mass.

Case Discussion

Peripheral primitive neuroectodermal tumors (pPNET) are one of several of tumors with similar histology, composed of relatively uniform primitive small round blue cellsThey tend to be large and aggressive retroperitoneal tumors and share many demographic, radiographic and clinical similarities.

This case is also about the importance of clinico-radiological correlation and not being distracted by 'red herrings'.  In this case the nature of the trauma in a young patient not correlating with the extent of what was a presumed hematoma on the initial MRI.

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Case information

rID: 48497
Published: 20th Oct 2016
Last edited: 20th Oct 2016
Inclusion in quiz mode: Included

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