Age / Sex : 68 / F

Chief complaint : Palpable mass (History of breast cancer)

What is your impression?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Soo-Jung Choi, Gangneung Asan Hospital

Discussion

Answer:  Muscular sarcoidosis

Findings: There is a well enhancing tubular mass like lesion with T1 high SI in the medial gastrocnemius muscle. Central star shaped scar (T1 low SI portion) is noted on axial images and three stripe sign is noted on coronal images.

Differential Diagnosis:

muscular sarcoidosis

intramuscular metastasis/lymphoma

fibromatosis (desmoid tumor)

Discussion: Muscular sarcoidosis

Muscular involvement of sarcoidosis is rare and occurs in two forms: nodular and myopathic. In the nodular variety, patients have single or multiple nodules in the skeletal muscles.

In the nodular type of muscular sarcoidosis, the lesions were long and extended along muscle fibers. Axial MR images showed a star-shaped central structure of decreased signal intensity. Coronal and sagittal MR images showed three stripes, including an inner stripe of decreased signal intensity and outer stripes of increased signal intensity. After IV injection of gadopentetate dimeglumine, contrast-enhanced MR images showed enhancement in the peripheral area of the lesions of the nodular type. On sonograms, the central structure was hyperechoic and the peripheral area was hypoechoic relative to surrounding tissue.

References:

S Otake. Sarcoidosis involving skeletal muscle: imaging findings and relative value of imaging procedures. AJR 1994;162:369-375.