ARRS 2022 Abstracts

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E1316. Glomus Tumor: A Rare Cause of Knee Pain
Authors
  1. Pui Yang Carol Chien; Queen Mary Hospital
  2. Kam Ho Victor Lee; Department of Diagnostic Radiology, LKS Faculty of Medicine, HKU; Imaging and Interventional Radiology Centre, CUHK Medical Centre
Background
A glomus tumor is a rare benign neoplasm arising from the glomus body of the skin. It occurs most frequently at the subungual region of fingers and toes. Patients usually present with disturbing symptoms including severe pain and hypersensitivity to cold. Atypical extradigital locations are extremely uncommon, which makes diagnosis challenging. Identifying the typical clinical and radiological presentation aids accurate diagnosis. Early surgical excision gives promising results. We report a rare case of a glomus tumor at the anterior aspect of the knee joint with radiological and pathological correlation.

Educational Goals / Teaching Points
The goals of this exhibit are to review the clinical presentation and pathophysiology of a glomus tumor, with radiological and pathological correlation; review the ultrasound and MRI imaging appearance of a glomus tumor; highlight the pathognomonic features of this rare tumor that differentiate it from other differentials (in particular, hemangioma and vascular malformation); highlight special ultrasound techniques and MRI sequence in assessment of soft tissue tumor, with special focus on glomus tumors; and discuss the treatment options for a glomus tumor.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
A glomus tumor is a rare benign vascular tumor arising from the dermal neuromyoarterial glomus body, which is a specialized arteriovenous anastomosis responsible for blood flow and thermoregulation of the skin. It consists of variable amount of glomus cells, prominent branching vascular channels, and smooth muscle cells. It only accounts for 1.6% of all soft tissue tumors, with typical location at the subungual region of the extremities. Extradigital glomus tumors are rare and represent about 30% of all glomus tumors. The classic triad of symptoms is paroxysmal pain, cold intolerance, and extreme tenderness to touch, which is noted in 63–100% of cases. Only less than 20% of cases were diagnosed correctly preoperatively, with the most common misdiagnoses reported as hemangioma, neuroma, and neurofibroma. On ultrasound, a glomus tumor presents as a hypervascular well circumscribed hypoechoic subcutaneous nodule. In contrast to haemangioma, glomus tumors are not as compressible. Calcifications are typically absent. The classic “vascular stalk” sign was found in 67% of glomus tumors and was also present in our case. On MRI, glomus tumor is a circumscribed homogenously vividly enhancing T2W hyperintense mass. MRA was shown to be a useful noninvasive technique in additional to conventional MRI for establishing the diagnosis and detection of recurrence. Typical findings include early and marked enhancement in arterial phase and tumor blush in venous and delayed phase. Good ultrasound technique including gentle pressure and optimal Doppler settings are essential for diagnosis, which will be discussed in the presentation.

Conclusion
Extradigital glomus tumors are rare benign neoplasms. Understanding the pathophysiology, clinical presentations, and typical imaging findings aids early diagnosis. Surgical excision of the tumor gives promising results.