Features of MRI honeycomb edema signals in cancer-associated dermatomyositis patients: a brief report.

Dermatomyositis (DM) is an autoimmune inflammatory disease that is a possible paraneoplastic phenomenon. The aim of this study was to explore the difference in thigh MRI findings between DM patients with and without cancer to further assist clinicians in the early discovery of underlying malignancy. Thigh muscle MRI with T2 fs/STIR images obtained from 47 patients diagnosed with DM at a single center were retrospectively assessed for the involvement of muscle compartments, as well as the pattern and distribution of the edema signal. Among 47 patients, 14 had cancer within three years of DM diagnosis. Honeycomb edema signals were more frequently observed in cancer patients (10 in the cancer group, 11 in the noncancer group, p = 0.020), while foggy signals were not found in cancer patients. Among patients with honeycomb signals, we found that cancer patients had a relatively longer disease duration (p = 0.012), lower creatine kinase levels (p = 0.011), and barely showed adductor involvement (p = 0.016). Logistic regression analysis identified honeycomb edema signals in the quadriceps without adductor involvement as an independent risk factor for having cancer in DM patients. Honeycomb pattern edema signals showed in quadriceps but not adductors on thigh muscle MRI STIR/T2 fs sequence were more frequently found in cancer-associated DM patients. Key points • MRI honeycomb edema signals in the quadriceps without adductor involvement may be a predictor for underlying cancer in DM patients.