Glomus tumor is a benign vascular neoplasm arising from modified smooth muscle cells (glomus cells) of the normal glomus body (arteriovenous anastomosis). It is most commonly located subungually (beneath the nail bed) and is characterized by the classic triad of paroxysmal pain, point tenderness, and cold intolerance. It is usually small (<1cm). US is the primary diagnostic modality and appears as a small, well-defined, hypoechoic solid mass in the subungual region. Markedly intense vascularity (hypervascular) disproportionate to lesion size on Doppler is a pathognomonic finding.
Age Range
20-60
Peak Age
40
Gender
Female predominant
Prevalence
Rare
Glomus tumor arises from neoplastic proliferation of modified smooth muscle cells (glomus cells) in glomus bodies involved in thermoregulation. Glomus bodies are normally arteriovenous anastomosis structures that function in skin temperature regulation — they are particularly dense in fingertips and nail beds. This dense vascular network is the fundamental reason for the hypervascular appearance of glomus tumor on US: tumor cells preserve arteriovenous connections and create low-resistance vascular pathways. Prominent arterial flow and low resistive index on Doppler reflect this arteriovenous shunting. The pain mechanism relates to the density of mast cells and nerve fibers within the tumor — glomus cells compress nerve endings and secrete vasoactive substances. Cold intolerance results from disruption of the thermoregulatory function of the glomus body — vasospasm of vessels within the tumor during normal cold-induced vasoconstriction provokes pain. The hypoechoic appearance on US results from dense and compact packing of glomus cells — the homogeneous cell population creates a uniform tissue with low acoustic impedance.
Intense arterial-venous flow filling the entire tumor in a small subungual mass is the pathognomonic Doppler finding of glomus tumor, reflecting preservation of the arteriovenous structure of the normal glomus body.
On B-mode US, glomus tumor appears in the subungual region (beneath the nail bed) as a small (<1cm, usually 3-8mm), well-defined, oval or round, homogeneous hypoechoic solid mass. The mass is adherent to or very close to the ventral surface of the nail plate. Pressure erosion may be seen in the dorsal cortex of the distal phalanx.
Report Sentence
A small, well-defined, homogeneous hypoechoic solid mass is seen beneath the nail bed in the subungual region, consistent with glomus tumor.
On color and power Doppler, glomus tumor demonstrates markedly intense hypervascularity disproportionate to lesion size — even in a 5mm mass, arterial and venous flow filling the entire tumor is seen. This disproportionate vascularity is the pathognomonic Doppler finding of glomus tumor. Low-resistance arterial flow pattern and low RI (<0.5) on spectral Doppler reflect arteriovenous shunting.
Report Sentence
Markedly intense vascularity disproportionate to lesion size with low RI is identified within the subungual mass on power Doppler, the pathognomonic finding of glomus tumor.
On high-resolution US, nail plate deformity or thinning due to glomus tumor may be seen. Saucer-shaped erosion in the dorsal cortex of the distal phalanx reflects chronic pressure effect. Bone erosion indicates the lesion has been present for a long time. These bony changes can also be confirmed with radiography and CT.
Report Sentence
Focal erosion of the distal phalanx dorsal cortex is noted, related to glomus tumor.
On MRI T2, glomus tumor appears as a markedly hyperintense, well-defined small mass. T2 hyperintensity reflects the tumor's high vascularity and cellular water content. Subungual location and bone erosion are optimally evaluated on T2.
Report Sentence
A markedly hyperintense small mass is seen in the subungual region on T2, consistent with glomus tumor.
On contrast-enhanced MRI, glomus tumor shows intense homogeneous enhancement — reflecting the hypervascular structure. Enhancement distinctly separates the tumor from surrounding normal tissue and is helpful for surgical planning.
Report Sentence
The subungual mass shows intense homogeneous enhancement on post-contrast sequences, consistent with glomus tumor.
On spectral Doppler, arterial flow within glomus tumor shows low RI (<0.5) — direct indicator of arteriovenous shunting. Continuous forward flow throughout diastole is present. This low RI pattern is distinctly different from the high-resistance flow (RI >0.7) in normal digital arteries.
Report Sentence
Arterial flow within the lesion shows low resistive index (RI <0.5) on spectral Doppler, supporting arteriovenous shunting and glomus tumor.
Criteria
Solid, well-defined, homogeneous glomus cell proliferation, most common subungual
Distinct Features
Most common type (75%). Usually solitary, small (<1cm), painful. Surgical excision is curative.
Criteria
Glomus cells + prominent vascular component (cavernous hemangioma-like), may be multiple
Distinct Features
20% of all glomus tumors. Larger, less painful, may be multifocal. More heterogeneous on US.
Criteria
Glomus cells + prominent smooth muscle component, larger size
Distinct Features
Rare (5%). More common in deep location. More heterogeneous and less vascular on US. Less painful than classic glomus tumor.
Distinguishing Feature
Giant cell tumor is peritendinous, low vascularity, larger and painless. Glomus tumor is subungual, hypervascular, small and painful.
Distinguishing Feature
Foreign body granuloma shows hyperechoic foreign body + shadowing. Glomus tumor is homogeneously hypoechoic and hypervascular.
Distinguishing Feature
Hemangioma occurs in infants and shows involution. Glomus tumor typically occurs in adults (30-50 years) and does not show spontaneous regression.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
12-monthTreatment of glomus tumor is surgical excision and is curative. Preoperative localization with US increases surgical success rate. Recurrence rate after surgical excision is 5-10%, usually due to incomplete resection. Malignant glomus tumor (glomangiosarcoma) is extremely rare.
Glomus tumors are benign and surgical excision is curative. Classic triad: localized pain, cold sensitivity, point tenderness (Love test). Preoperative US and MRI are important for surgical planning. Multiple glomus tumors are rare and should not be confused with glomuvenous malformation.