Age / Sex : 67 / F

Chief complaint : Right lower leg mass (onset: 3MA)


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


Courtesy : 강유선, Yusuhn Kang 분당서울대학교병원, Seoul National University Bundang Hospital

Muscular sarcoidosis

Discussion

Findings:

An ill-defined mass lesion is noted within the medial head of the gastrocnemius muscle. The mass shows an

umbilicated appearance, with hyperintensity in the periphery and low signal intensity centrally on T2-weighted and T1

contrast-enhanced images (“dark star” sign). On coronal image, the lesions shows an elongated appearance with an

inner stripe of decreased signal intensity and outer stripes of increased signal intensity (“three stripe” sign).

Differential Diagnosis:

Desmoid-type fibromatosis.

Intramuscular lymphoma

Discussion:

 Muscular involvement of sarcoidosis is rare; reported in 1.4% of known sarcoidosis cases. It occurs in two forms:

nodular form which manifest as sigle or multiple nodules within the skeletal muscle, and a myopathic form which

shows diffuse muscle signal changes resembling polymyositis.

Axial MR images showed a central star-shaped area of decreased signal intensity and peripheral hyperintensity on T2-

weighted and T1 contrast-enhanced images (“dark star” sign).. Coronal and sagittal MR images shows three stripes,

including an inner stripe of decreased signal intensity and outer stripes of increased signal intensity. Histologically, the

lesions show central fibrotic tissue, corresponding to the dark signal intensity noted at the center of the lesion on T2

and T1 contrast enhanced images. Active inflammatory granuloma containing epitheloid cells are noted in the

periphery of the lesion, which corresponds to the hyperintensity on T2-weighted images and contrast enhancing areas

on T1 contrast-enhanced images.

References:

1. Moore, Sandra L., and Alvin E. Teirstein. "Musculoskeletal sarcoidosis: spectrum of appearances at MR imaging." Radiographics23.6 (2003): 1389-1399.


2. Tsujimoto, Naoki, et al. "Three stripes sign: muscle involvement with internal fibrosis in a patient with sarcoidosis." Case Reports2014 (2014): bcr2014204691.


3. Moore, Sandra L., Alvin Teirstein, and Cornelia Golimbu. "MRI of sarcoidosis patients with musculoskeletal symptoms." American Journal of Roentgenology185.1 (2005): 154-159.