Diagnostic imaging findings of subcutaneous mast cell tumor in a dog

A 5-year-old Labrador Retriever presented with a subcutaneous mass on the right scapular region with localized calor. On magnetic resonance imaging (MRI), a heterogeneously hypointense mass was seen on T1-weighted images (WI) and hyperintense on T2WI and fat-suppressed T2WI with marginal contrast enhancement on postcontrast T1WI and invasion into the surrounding tissue. Histopathological examination of the mass confirmed subcutaneous mast cell tumor (MCT) infiltrating to the adjacent subcutaneous fat. This is the first report to describe the MRI findings of subcutaneous MCT in veterinary medicine. This study suggests that MRI may help evaluate the extent of invasion of subcutaneous MCT.