A 55 years old male presented with mild to moderate pain in the tip of little finger of right hand, which increased in cold temperature. Clinical examination showed point tenderness in fingertip predominantly at the pulp region. There was also bluish discolouration of fingertip (Fig.1). There was no history of trauma. Patient was referred for musculoskeletal ultrasonography (USG).
High-Resolution ultrasonography(HRUS) showed a well-defined, oval, hypoechoic lesion in the pulp of little finger of right hand. Color Doppler revealed marked internal and perilesional vascularity. Spectral Doppler demonstrated low resistance flow with peak systolic velocity (PSV) – 10.2 cm/sec. On elastography lesion had soft consistency compared to flexor tendons. Approximate size of lesion was 3 x 2 mm.
MRI was also performed. The lesion appeared hyperintense on PD fat sat (PDFS) images and hypointense on T1W images. On administration of contrast, the lesion showed intense homogeneous enhancement on arterial phase. No underlying bony erosion was seen. Adjacent tendons and their sheaths were unremarkable.
Based on these clinical and imaging findings, the diagnosis of glomus tumour was made.
Glomus tumour, also known as Glomangioma, is a benign tumour of glomus body. Histopathologically, it is a hamartoma that arises from neuromyoarterial apparatus (glomus body). Glomus bodies are responsible for thermoregulation. Glomus tumours can be seen in any area of the body; however up to 75% are found in the hand, more specifically in the fingertips. These are predominantly seen in subungual space but may also visualized in the finger pulp. Usual age of presentation is 3rd to 5th decades of life.
Literature has described the classic triad of pain, temperature sensitivity, and point tenderness. However, not all three may be present in same case. Overlying skin or nail may show discolouration.
Typical USG findings of glomus tumour include well defined solid and hypoechoic mass in fingertip, predominantly in the subungual space. On colour doppler, this lesion appears hypervascular secondary to the high-velocity flow in intratumoral shunt vessels. This finding is specific for diagnosis.  The intralesional vascularity is not seen in other fingertip lesions like mucous cyst and epidermoid inclusion cyst. Spectral doppler shows low-velocity flow with PSV ranges between 4.9 to 25.6 cm/s and resistive index ranges from 0.46 to 0.71.On MRI it usually appears hyperintense on T2 and hypointense on T1. On post-contrast images, it shows intense homogeneous enhancement. MR angiographic findings reveal areas of intense homogeneous arterial phase enhancement along with tumour blush, which increases in size in the delayed phase.
In the current scenario, MRI is most frequently recommended modality for imaging and preoperative assessment of glomus tumors. Although this has disadvantages like use of intravenous contrast and less accurate in detection of smaller tumours (<3 mm in diameter). Due to recent advances in HRUS, it is possible to identify small glomus tumors in real time without any need of intravenous contrast media. HRUS also provides decent idea about the intralesional vascularity. One of the biggest advantages of is that we can compare pathologic finger/limb with normal or contralateral one. Due to these advantages, HRUS may play a larger role in the preoperative planning of glomus tumours in near future.
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