Age / Sex : 77 / F

Chief complaint: Right thigh growing swelling and tenderness for 8 months

Falled down on his right side in mountain 8 months ago

Surgery for stomach cancer 9 years ago

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

* Send Application Answers to Jae Hyuck Yi, MD ([email protected])
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Courtesy : Won-Hee Jee, MD, Seoul St. Mary’s Hospital

Primary lymphoma of the muscle

Discussion

Findings: A long segmental muscle mass is seen in the right hip and extends to medial and posterior compartment of right thigh. Involved muscles are markedly enlarged. It is relatively homogeneous on T1- and T2WI and contains septations and traversing vessels. It shows intermediate to hypointense T2 signal and diffuse enhancement. The lesion shows very low ADC values. Right sciatic nerve is encased by the mass and femoral neurovascular vessels are displaced anterolaterally. Adjacent subcutaneous fat shows streaky infiltrations with skin thickening.

Differential Diagnosis: MFH, leiomyosarcoma, liposarcoma, metastasis

Diagnosis: Primary muscle lymphoma

Discussion: Primary lymphoma of the muscle is rare among soft tissue tumors. Among lymphomas it is also infrequent representing 1.5% of cases of non-Hodgkin's lymphoma and 0.3% of Hodgkin's lymphoma. Involvement of muscle may be from systemic disease, be an extension of lymphomatous deposits in adjacent lymph nodes and bone, or, least commonly, be from a primary lesion as seen here. The usual clinical symptoms are local swelling and pain or systemic symptoms such as fever, sweating, and weight loss. The tumor can be indolent or rapidly progressive. Commonly present  locations include extremities such as the leg, thigh and arms but is also seen in the trunk. The inclusion of lymphoma in the differential diagnosis of soft tissue tumors is important in relevant cases as the pathologic diagnosis may be influenced by usage of special staining procedures. Skeletal muscle lymphoma responds well to chemotherapy with or without radiation therapy, unlike other malignant soft tissue tumors. Among treatment options, to avoid unnecessary surgery, the correct diagnosis is required. However, differentiation of skeletal muscle lymphoma from various neoplastic and inflammatory diseases is often difficult on the basis of clinical findings alone. On MR imaging the involvement of skeletal muscle by lymphoma may be suspected in cases of diffuse muscle enlargement with a long segmental, multicompartmental involvement, deep fascia involvement, traversing vessels in the lesion, subcutaneous stranding, skin thickening, and extension along neurovascular bundles. Skeletal muscle lymphoma can reveal peripheral thick band-like enhancement or marginal septal enhancement, in addition to a well-known diffuse homogeneous contrast enhancement. Most lesions show intermediate to hyperintenseT2 signal with intermediate to low T1 signal. Occasionally, lymphadenopathy may be seen which helps the diagnosis.

References

1. Chun CW,Jee WH, Park HJ, et al. MRI Features of Skeletal Muscle Lymphoma. AJR 2010;6:1355-1360

2. Suresh S, Saifuddin A, O'Donnell P. Lymphoma presenting as a musculoskeletal soft tissue mass: MRI findings in 24 cases. Eur Radiol 2008;18:2628 –2634

3. Eustace S, Winalski C, McGowen A. Skeletal muscle lymphoma: observations at MR imaging. Skeletal Radiol 2007;36:937-944

4. Lee VS, Martinez S, Coleman RE. Primary muscle lymphoma: clinical and imaging findings. Radiology 1997;203:237–244