Popliteal glomangioma mimicking Baker's cyst in a 9-year-old child: an unusual location of a glomus tumor.

Popliteal cysts (Baker's cyst) are very common conditions in children. However, in the differential diagnosis of popliteal cysts in childhood, glomus tumor is the most infrequent diagnosis. This is a relatively uncommon soft tissue tumor that can occur at any age and any anatomic site, with a predilection for the subungual region. In the reported series, extradigital glomangiomas involving the knee are located in the patellar ligament, quadriceps tendon, patellar fat pad, and popliteal fossa. In this study, I present a second case of glomus tumor located in the popliteal fossa and misdiagnosed as a Baker's cyst. I also review the "around-the-knee glomus tumors" that have been discussed in the literature to date.