Imaging description

The majority of cases of medial epitrochlear lymphadenopathy are reactive or benign in origin. One of the more common benign causes is cat scratch disease. It can occasionally be seen with radiography as a soft tissue mass in the medial epitrochlear area. It is much more commonly seen on MRI as a soft tissue space-occupying lesion in the medial epitrochlear region. On MRI, the lesion is typically round or ovoid in shape, has slightly hyperintense signal on T1-weighted images, has hyperintense signal on T2-weighted images, and shows homogeneous enhancement on postcontrast images (Figure 31.1). The lesion can contain areas of necrosis which are seen as areas of heterogeneous signal intensity and areas of no enhancement. The lesion in cat scratch disease is a reactive lymph node. The more common locations for reactive lymphadenopathy from cat scratch disease are the medial epitrochlear area, the axillary region, and the groin. Patients can have pustule formation in the wrist and distal forearm area as well. By US, the mass may have the appearance of a large reactive lymph node (Figure 31.2).

Importance

It is important to know that a medial epitrochlear mass is usually benign and most commonly is a manifestation of cat scratch disease so that unnecessary surgery does not occur. The lesion (reactive lymphadenopathy) does not need to be resected. Cat scratch disease is usually diagnosed clinically using the history, physical exam findings, and laboratory tests (serology for antibodies to Bartonellahenselae). A history of a cat scratch or physical exam findings of a cat scratch involving the hand, wrist, or distal forearm helps confirm the diagnosis; however, it is not mandatory to make the diagnosis. In one larger study, the age range for this disease was 6–63 years old. It is important to suspect this disease when imaging a medial epitrochlear mass so that unnecessary work-up or surgery for malignancy is not performed.