Glomus tumor overview

# Overview
Glomus body was first discovered by Wood, a Scottish surgeon, in 1812 in the Edinburgh Medical Journal. However, Glomus tumor was first correctly described in 1924 by Barre and Masson. Glomus tumor arises from modified smooth muscle cells (or pericytes) of the glomus body (previously called as glomus cells). Glomus tumors may be classified into solitary and multiple variants.  On gross pathology, they are small (usually less than 1 cm), bluish or whitish, well circumscribed, solitary nodules are characteristic findings of glomus tumor. On microscopic histopathological analysis, branching vascular channels and aggregates of specialized glomus cells are characteristic findings of glomus tumor. Multiple glomus tumors are caused by a mutation in the GLMN (glomulin) gene. Solitary glomus tumors must be differentiated from other diseases that cause pain such as leiomyoma and eccrine spiradenoma. Multiple glomus tumors must be differentiated from other diseases such as cavernous hemangioma and blue rubber bleb nevus syndrome. Solitary glomus tumors commonly affect young to middle aged individuals. Multiple glomus tumors commonly affect children. Females are more commonly affected with solitary glomus tumors (particularly subungual lesions) than males. Males are more commonly affected with multiple glomus tumors than females. Common risk factors in the development of glomus tumors are age and gender. If left untreated, patients with glomus tumors may progress to develop pain and nail discoloration. Common complication of the glomus tumor includes malignant change in multiple tumors. Common complications of glomus tumors post operatively include nail deformities and recurrence. Findings on x rays suggestive of glomus tumor may include a marginated bone erosion or thinning of the adjacent cortical bone. MRI and ultrasound may be helpful in the diagnosis of glomus tumors. Surgery is the mainstay of treatment for glomus tumor. Prognosis is generally excellent for solitary glomus tumors and malignant glomus tumors treated with wide excision. However, the prognosis is poor for malignant glomus tumors with widespread metastases.

# Historical Perspective
Glomus body was first discovered by Wood, a Scottish surgeon, in 1812 in the Edinburgh Medical Journal. However, Glomus tumor was first correctly described in 1924 by Barre and Masson.

# Classification
Glomus tumors may be classified into solitary and multiple variants.

# Pathophysiology
Glomus tumor arises from modified smooth muscle cells (or pericytes) of the glomus body (previously called as glomus cells). The glomus body is a neuromyoarterial plexus in the dermis of skin that is normally involved in thermoregulation. The gene involved in the pathogenesis of familial glomangioma is the glomulin (GLMN) gene. On gross pathology, small (usually less than 1 cm), bluish or whitish, well circumscribed, solitary nodules are characteristic findings of glomus tumor. On microscopic histopathological analysis, branching vascular channels and aggregates of specialised glomus cells are characteristic findings of glomus tumor.

# Causes
The cause of solitary glomus tumors has not been identified. Multiple glomus tumors are caused by a mutation in the GLMN (glomulin) gene.

# Differentiating Glomus Tumor from other Diseases
Solitary glomus tumors must be differentiated from other diseases that cause pain such as leiomyoma and eccrine spiradenoma. Multiple glomus tumors must be differentiated from other diseases such as cavernous hemangioma and blue rubber bleb nevus syndrome.

# Epidemiology and Demographics
The exact incidence of glomus tumors is unknown. Females are more commonly affected with solitary glomus tumors (particularly subungual lesions) than males, while multiple lesions are slightly more common in males. Solitary glomus tumors can occur at any age; however, multiple glomus tumors commonly affect children.

# Risk Factors
There are no established risk factors for glomus tumor; however, an epidemiologic relationship may exist between glomus tumors and neurofibromatosis.

# Screening
Screening for multiple glomus tumors by genetic testing is recommended among individuals with a family history of glomangiomas (autosomal dominant inheritance).

# Natural History, Complications and Prognosis
If left untreated, patients with glomus tumors may progress to develop pain and nail discoloration. Common complication of the glomus tumor includes malignant change in multiple tumors. Common complications of glomus tumors post operatively include nail deformities and recurrence. Prognosis is generally excellent for solitary glomus tumors and malignant glomus tumors treated with wide excision. However, the prognosis is poor for malignant glomus tumors with widespread metastases.

# Diagnosis

## Diagnostic Study of Choice
There is no single diagnostic study of choice for the diagnosis of glomus tumor, but glomus tumors can be diagnosed based on MRI of the finger in addition to history and physical examination.

## History and Symptoms
A detailed history from the patient may be helpful. A positive history of trauma may be present. A positive family history may be present in patients with multiple glomus tumors (autosomal dominant). Symptoms of glomus tumor include hypersensitivity to cold and paroxysmal pain at a well defined site.

## Physical examination
Patients with glomus tumor usually appear well. Physical examination of patients with glomus tumor is usually remarkable for small (usually less than 2cm), blue or red palpable nodules which are usually distributed in the acral regions (subungual most common) and nail deformities.

## Laboratory Findings
There are no diagnostic laboratory findings associated with glomus tumor.

## Electrocardiogram
There are no ECG findings associated with glomus tumor.

## X Ray
X rays may be helpful in the diagnosis of glomus tumor. Findings on x rays suggestive of glomus tumor may include a marginated bone erosion or thinning of the adjacent cortical bone.

## Echocardiography and Ultrasound
Ultrasound may be helpful in the preoperative diagnosis of glomus tumor; it provides the localization, size, and shape of tumors as small as 3 mm. Findings on an ultrasound suggestive of glomus tumor include a well-circumscribed hypoechoic mass.

## CT Scan
There are no CT findings associated with glomus tumors.

## MRI
An MRI may be helpful in the diagnosis of glomus tumor. Findings on MRI suggestive of glomus tumor include slightly hypointense or hyperintense T1 images and hyperintense T2 images.

## Other Imaging Findings
There are no other imaging findings associated with glomus tumor.

## Other Diagnostic Studies
Other diagnostic studies for glomus tumor include immunohistochemistry staining, which demonstrates glomus cells positive for vimentin and alpha-smooth muscle actin and negative for desmin.

# Treatment

## Medical Therapy
The predominant therapy for solitary glomus tumor is surgical resection. Patients with multiple glomus tumors are treated with sclerotherapy or laser therapy.

## Surgery
Surgery is the mainstay of treatment for glomus tumor.