Glomus tumor

Tumor biology and incidence

Rare (~1.5% of soft tissue tumors of the hand), generally benign neoplasms
- In isolated cases, may be locally aggressive and even metastasize (then called glomangiosarcoma)
Characterized by proliferation of glomus cells (specialized smooth muscle cells that surround small vessels and play a role in regulation of peripheral blood flow); etiology unknown
Arise from arterial part of glomus body -- specifically, Sucquet-Hoyer canal (arteriovenous shunt in dermis that helps regulate temperature)
Primarily solitary tumors, although multiple tumor variant (inherited in an autosomal-dominant pattern with invariable penetrance) occurs in 10% to 25% of cases
- Multiple tumor variant subdivided into three types: regional (localized to specific area), disseminated (multiple lesions widely distributed throughout body), congenital (very rare; coalesce into plaques)

Age

Most common between 30 and 50
Multiple tumor variant tends to present in second or third decade of life

Gender

Solitary tumor: F > M
Multiple tumor variant: F = M, or slight male predominance

Presentation

Classic triad of paroxysmal pain, tenderness to palpation, and cold sensitivity
Pain often excruciating, though less severe in multiple tumor variant
Can have nailbed ridging and bluish discoloration at base of nail

Physical findings

Solitary tumors usually bluish or purplish in color, smaller than 1 cm, and located in acral areas (especially subungual)
Highly tender to palpation
Range from nodular to faintly papular
Rare malignant tumor tends to be larger, deeper, and more rapidly growing

Plain films

May show bony erosion in up to half of subungual lesions

Site

Can present in various locations but most commonly found in hand (75%), particularly in subungual region

Size

<1 cm

Tumor effect on bone / bone response to tumor

Bone eroded by tumor in some cases
Osteolytic appearance, usually with sclerotic, well-defined border due to slow growth

Matrix

None

Cortex

Cortical erosion in 20-50% of cases

Soft tissue mass

Often see increased distance between nailplate and dorsal soft tissue, indicating presence of mass

CT scan

Shows non-specific subungual mass
Delineates bony erosion if present

MRI

Appear as dark, well-delineated lesions on T1 images
Very high and homogeneous signal on intensity on T2-weighted images
Useful in detecting small fingertip lesions
High-resolution MRI better for delineating extent of lesion

Differential diagnosis

Blue nevi
Hemangioma
Neuroma
AVM
Angiolipoma
Tufted angioma
Angioleiomyoma
Melanoma
Epidermal inclusion cyst
Metastatic carcinoma
Osteoid osteoma
Enchondroma
Chronic osteomyelitis.

Natural history

Exquisitely painful until treated
Excision usually cures solitary lesion, with very low recurrence rate
Malignant tumors extremely rare, locally aggressive, prone to recur, and can metastasize (few case reports)

Pathology

Solitary lesion

Gross: Well-circumscribed nodules surrounded by fibrous tissue
Micro: Clusters of glomus cells, which have rounded, regular shape with sharply punched-out, rounded nucleus and scant eosinophilic cytoplasm
- Glomus cells and fine, nonmyelinated nerve endings located between endothelial-lined vascular spaces.

Multiple lesions

Grossly and histologically appear more like hemangiomas, with larger vascular channels and smaller aggregates of glomus cells, compared to solitary lesions

Malignant glomus tumor

Similar to benign glomus tumor, but tends to show mild atypia, shorter and more spindly nuclei, various rate of mitosis, and more invasive growth pattern

Diagnosis and treatment

Hildreth sign: Disappearance of pain after application of tourniquet proximally; reported sensitivity of 77.4% and specificity near 100%.
Love test: Pain elicited by applying pressure to precise area with pin or tip of a sharp pencil; sensitivity 100% according to some sources
Cold sensitivity: Jighly sensitive and specific as well
Excision is treatment of choice for solitary glomus tumor
- Tumor fairly well encapsulated and can be shelled out
- Can be approached via lateral approach or directly under nailbed
- Pain relief typically immediate following surgery
For multiple glomus tumors, surgical treatment usually limited to most symptomatic lesion(s)
- Other methods -- including sclerotherapy, electron beam radiation, argon lasers, and carbon dioxide lasers -- have been used to treat multiple lesions, with good results reported in literature

Complications

Recurrence (as high as 20%)
If symptoms continue longer than 3 months post-op, re-exploration indicated to look for missed/recurrent lesion