Glomus tumour eroding the medial facet of the patella: a case report.

Glomus tumours are benign lesions occurring essentially in the hand, with a predilection for the subungueal area. Even though they have been reported in literature, extradigital localisations of glomus tumours are frequently misdiagnosed; they never lead to bone osteolysis. We report the case of a patient who presented with a typical patellofemoral syndrome due to a glomus tumour that eroded the medial facet of the patella. MRI, which is the gold standard for the diagnosis, showed a well-delineated spherical tumour with enhancement after Gadolinium injection. CT Scan excluded an osteoid osteoma and showed the erosion of the patella. The lesion was surgically resected and the histological examination established the definitive diagnosis.