Presentation
Low back and left leg pain. L4/L5 distribution weakness. Absent left knee and ankle jerk.
Patient Data
15 x11 cm left intramuscular mass within the psoas/iliopsoas muscle, abutting the ilium. No cortical bone destruction.
The mass compresses the distal left L5 nerve root.
Minor L4/L5 degenerative change.
L1 conus. Normal cauda equina.
12.5 x 10 cm mass arising from the left iliopsoas muscle. No bony destruction.
Fatty liver. The remainder of the solid organs are normal.
No adrenal or peritoneal nodules. No infradiaphragmatic lymphadenopathy. No sinister bone lesion.
2 cm simple right ovarian cyst. Minor sigmoid diverticulosis.
Comment: Left pelvic mass - most likely a sarcoma
The mass is amenable to ultrasound guided biopsy if required.
SPECIMEN: Biopsy of left retroperitoneal mass
CLINICAL DETAILS: Large mass in iliopsoas fascia.
MACROSCOPY: Two cores of cream tissue measuring 6 and 3 mm, plus blood clot, plus fragments. Image guided biopsy undertaken
Block key: A1 = larger core.
MICROSCOPY: These are needle cores of tissue from a tumor consisting of a uniform population of medium-sized spindle cells with a high nuclear to cytoplasmic ratio arranged in a clustered and vesiculated pattern with some areas of nuclear palisading. Initial immunohistochemistry shows the following findings: CD99 - weakly expressed. Broad spectrum cytokeratins (using the AE1/AE3 antibody), EMA, CD34, S100, smooth muscle actin, desmin, STAT6 - not expressed. The morphological appearances are consistent with this being a sarcoma with synovial sarcoma, malignant peripheral nerve sheath tumor and Ewing family tumors being possible diagnoses. Further testing (fluorescence in situ hybridization for EWSR-1 and SS18 rearrangements and immunohistochemistry for H3K27me3) is awaited and a supplementary report will be issued when the results are available.
CONCLUSION: Needle core biopsy, left retroperitoneal mass - poorly differentiated malignancy, probably sarcoma, awaiting further tests.
Large soft tissue mass overlying the left paravertebral region.
Case Discussion
One of the less common causes for a patient presenting with an L4/L5 compressive radiculopathy from a physiotherapy referral.
Make sure you look at the localizer and image edges of MR studies of the lumbar spine.
I don't think many would get that soft tissue mass on the pelvic x-ray, but once you know it's there is very visible!
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