SPR Unknown Case #33 -- Final
SPR unknown 33
Publication Date: 2010-07-09
MRI (images 2-5, Sag T1, Sag post gad, Axial T2 fat sat, and Axial post gad): Broad, irregular area of increased T2 signal of the anterior subcutaneous tissues of the mid tibia with nodular areas of avid post-contrast enhancement. Normal underlying bone and marrow.
Subcutaneous granuloma annulare (SGA) is an uncommon benign, inflammatory lesion typically seen in the subcutaneous tissues of children between 2 to 5 years of age. Patents usually present with complaints of a growing, painless mass. Although there are four clinically distinct forms of granuloma annulare, the subcutaneous form occurs exclusively in children. The remaining subtypes are primarily clinical, dermatologic diagnoses and thus not seen radiologically (1-2). It is histologically indistinguishable from a rheumatoid nodule and has been previously been termed subcutaneous palisading granuloma, benign rheumatoid nodule, palisading granuloma nodosum, and pseudo-rheumatoid nodule (3).
SGA is most often seen in the pretibial location but has been reported elsewhere such as the buttocks, scalp, and upper extremity. It represents approximately 2% of benign masses and is reportedly one of the most commonly biopsied, benign lesions in childhood (2). Although uncertain, post traumatic, infectious and cell-mediated etiologies are theorized (1,3).
Radiographs reveal focal soft tissue swelling or superficial, soft tissue mass without calcification. At MR imaging, SGA is classically described as a localized, subcutaneous, nodular lesion that demonstrates low T1 and high T2 signal with avid post gad enhancement. There is also variable, surrounding T2 hyperintensity possibly representing perilesional edema. The MRI appearance has classical findings that, when coupled with the appropriate history, strongly suggest SGA (1,3,4).
- Kransdorf MJ, Murphey MD, Temple HT. Subcutaneous granuloma annulare: radiologic appearance. Skeletal Radiol 1998;27:266-270.
- Kransdorf MJ. Benign soft tissue tumors in a large referral population: Distribution of specific diagnoses by age, sex, and location. AJR 1995;164:395-402.
- Laor T. MR imaging of soft tissue tumors and tumor-like lesions. Pedatr Radiol 2004;34:24-37.
- Vandevenne JE, Colpaert CG, De Schepper AM. Subcutaneous granuloma annulare: MR imaging and literature review. Eur Radiol 1998;8:1363-65.