Glomus tumor: around the knee

Case contributed by Dr Bruno Di Muzio


Painful subcutaneous nodule at the medial aspect of the knee.

Patient Data

Age: 49 years
Gender: Male

MRI left knee

Within the superficial subcutaneous fat lying immediately superficial to the medial patellofemoral retinaculum is a 7 x 9 mm ovoid lesion that is isointense to muscle on T1, hyperintense on T2 and demonstrates homogeneous contrast enhancement. This lesion lies just inferior to the placed skin marker. The underlying medial patellofemoral retinaculum has a normal appearance. This lesion was present on the previous MRI from one year ago although has increased in size, previously measuring 4 x 6 mm. No other soft tissue masses.

The cruciate ligaments, menisci and collateral ligaments are intact. Focal cartilage fissuring with minimal subchondral cystic change within the midline of the femoral trochlea. Articular cartilage elsewhere is relatively unremarkable. Extensor mechanism is intact. Imaged popliteal neurovascular bundle is within normal limits.


US-guided core biopsy

The previously demonstrated lesion is characterized on ultrasound as a well defined hypoechoic nodule, measuring 7.9 mm in diameter, and showing prominent internal vascularity. Procedure: With the patient in supine position, the target nodule was identified by ultrasound. The skin was prepped and draped in usual sterile fashion. Local anesthesia was performed using 1% lignocaine. Under ultrasound guidance the core-biopsy procedure using a co-axial 14/13G true- cut needle was performed, and three fragments were obtained.

Case Discussion

Glomus tumors, also referred as glomangioma, typically are found in the fingers and toes (subungual) and account for less than 2% of all soft tissue tumors 1. Atypical locations, as in this case, may pose some difficulties for its clinical and imaging diagnosis. Atypical locations, as in this case, may pose some difficulties for its clinical and imaging diagnosis. 

Differentials for these lesions would include angioleiomyomas, neuromas, hemangiomas and other hamartomatous lesions of the subcutaneous tissue 1.

Complete surgical excision is the treatment of choice. 


MICROSCOPIC DESCRIPTION: Sections show multiple pieces of mildly inflamed amorphous acellular eosinophilic material within which are sheets of cells with scattered small blood vessels. The cells are polygonal and uniform, with round nuclei, powdery chromatin, and distinct cell outlines. There is no necrosis or mitoses, and no evidence of malignancy

IIMMUNOHISTOCHEMISTRY: The lesional cells stain diffusely and strongly with smooth muscle actin. They are negative for cytokeratins.

DIAGNOSIS: Left knee biopsy: Glomus tumor.

Special thanks to Dr Amy Ting and Dr Beng Lim, radiology consultants at the RMH.


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Case information

rID: 53754
Published: 10th Jun 2017
Last edited: 14th Aug 2019
Tag: rmh
Inclusion in quiz mode: Included

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