Presentation
4-month history of left loin pain, occasional malaise, with no fever, weight loss, or dysuria. No palpable mass. CRP 11.4 mg/dL, ESR 23, and LDH 232. HIV and TB tests were negative.
Patient Data
Heterogeneously enhancing soft-tissue abnormality within the left psoas muscle causing its moderate bulkiness, extending to retroperitoneal and left paraaortic regions causing lateral displacement of the left kidney and mild hydronephrosis. No calcification. The adjacent vertebrae and discs were normal. No solid visceral lesions and hepatosplenic enlargement were seen.
Whole-body gallium-67 scan and SPECT/CT showed abnormal intense tracer uptake within bulky left psoas muscle.
Case Discussion
Biopsy of left psoas abnormality revealed Non-Hodgkin B-cell lymphoma. Development of non-Hodgkin lymphoma (NHL) within skeletal muscle is infrequent, although extra-nodal sites containing lymphoid tissue can develop NHL 1. Diffuse large B-cell lymphoma accounts for 50% of soft tissue NHL and is the most common skeletal muscle lymphoma 2.
The unilateral bulkiness of psoas muscle in a patient with no prior history of TB and anticoagulation should alert the radiologist to raise the possibility of lymphoma and advise further imaging workup and/ or biopsy.
We did not perform magnetic resonance imaging in our patient as there was no vertebral or disc abnormality on computed tomography, and also patient was claustrophobic. However, a few reports in the literature have described it is high T1 and T2 signal intensity on MR imaging with diffusion restriction due to high cellularity 3.
Spontaneous psoas hematoma is rare and is usually associated with anticoagulation therapy with a high mortality rate, with chronologic changes on MR imaging 4. Psoas abscess can be primary (due to hematogenous spread of infection from an occult source or direct extension from TB spondylitis) or secondary (Crohn’s disease is the commonest cause), common in young Asian populations 5. History of contact with TB, a raised ESR, bony or chest findings, and laboratory tests are usually sufficient.
Clinicians and radiologists should be aware of this entity and include it in their differential possibility of any muscle mass.
Acknowledgment: Special thanks to Dr. Arifa Jamal (Consultant Internal Medicine, KFMMC, Dhahran), Dr. Lina Abdul Samad (Consultant Nuclear Medicine, KFMMC, Dhahran), and Dr. Adeel Qamar (Specialist Radiologist, KFMMC, Dhahran) for contributing towards this case.