Imaging features of subcutaneous sarcoidosis

The skinny on skin: MRI features of cutaneous and subcutaneous lesions detected on body MRI studies

The skin and subcutaneous tissues are inevitably imaged as part of most body MRI studies. Incidental or even symptomatic skin lesions may, therefore, be detected and present a diagnostic challenge for the radiologist. We aim to provide a comprehensive review, with illustrative examples, of the skin abnormalities encountered on body MRI studies in our busy academic radiology department.

Solitary subcutaneous sarcoidosis with massive chronic prepatellar bursal involvement

A 56-year-old man presented with a painless prepatellar mass of the left knee. MR images demonstrated a large, well-defined mass with heterogeneous intermediate signal intensity on T1- and proton density-weighted images. Mild, heterogeneous enhancement was noted after the intravenous administration of gadolinium. Diagnostic imaging included atypical soft-tissue infection, fibrogranulomatous reaction, gouty tophus, rheumatoid nodule and xanthoma or possibly malignancy. The histopathological examination revealed sarcoidosis involving the prepatellar bursa.

Sarcoidosis presenting as prepatellar bursitis

A 61-year-old woman complained of a subcutaneous mass in her right knee. MR images revealed a well-defined subcutaneous mass in the prepatellar region, containing some fluid and foci of short T2. The lesion showed some marginal contrast uptake after an administration of meglumine gadopentetate (Gd-DTPA), consistent with prepatellar bursitis. The pathological specimen, however, revealed subcutaneous sarcoidosis involving the bursa.

FDG PET in the clinical evaluation of sarcoidosis with bone lesions

We report a case of sarcoidosis with osseous involvement. Whole-body fluorine-18-fluorodeoxyglucose (FDG) PET scanning demonstrated multiple sites of FDG uptake in the hilar lymph nodes, right ulna, bilateral feet, and subcutaneous tissue of the extremities. FDG PET scanning provides useful information for the detection of sarcoidosis with systemic distribution, even when osseous lesions are included.