Large prepatellar glomangioma: A case report

•Large glomangioma appearing inrare, anteroinferior aspect of knee in healthy 49 year old male.•MR imaging detected intermediate signal intensity on T1, mixed signal intensity on T2, and marked signal enhancement with gadolinium.•Histology demonstrated large, dilated vessels surrounded by normal endothelial cells and infiltrating glomus cells which stained positively for smooth muscle actin.

IntroductionGlomangiomas are rare, benign tumors derived from the glomus body, typically presenting with the classic triad of pain, tenderness to palpation, and hypersensitivity to cold. Most commonly they present as a solitary lesion in the extremities, especially subungual, but they may present elsewhere.Presentation of caseWe describe the case of a large (64 mm × 59 mm × 41 mm) glomangioma on the anteroinferior aspect of a healthy 49 year old male’s knee. Symptoms included constant throbbing pain with intermittent stabbing sensations localized to the mass. The mass was evaluated first by magnetic resonance (MR) imaging and then by histopathology following excision.DiscussionAlthough rare, clinical diagnosis of glomangiomas may be sufficient in typical cases, however in atypical cases, like the one discussed here, further evaluation is often necessary. Here MR findings were suggestive of a glomangioma with low to intermediate signal strength on T1 and mixed signal strength on T2. Intravenous gadolinium infusion demonstrated marked heterogeneous enhancement of the lesion, as well as serpiginous vascular malformations surrounding the lesion. Histopathology following excision confirmed a benign glomangioma depicting monomorphic small, round eosinophilic cells with minimal atypia which stained positive for smooth muscle actin, and negative for cytokeratin, S-100 and CK-34 via immunohistochemistry.ConclusionThe following case report details an atypical presentation of a benign glomangioma anterior to the knee in a patient experiencing chronic minor trauma to the area. Diagnosis was suggested by clinical presentation and MR imaging, and was confirmed histologically.