Pathology of Glomus Tumour

Dr Sampurna Roy MD            2022       

The glomus tumour is a distinctive neoplasm which arises from modified smooth muscle cells of the normal glomus body. The 2013 WHO classification of soft tissue tumours includes glomus tumors, myopericytoma, myofibroma and angioleiomyoma as members of the pericytic family of neoplasms.
 

[ The glomus body is a specialized form of arteriovenous anastomosis which is involved in temperature regulation.

There is a central coiled canal known as Suquet-Hoyer canal which is lined by plump endothelial cells.

This is surrounded by longitudinal and circular muscle fibres containing rounded epithelial appearing glomus cells. ]

Glomus tumours are commonly located in the subungual region of finger. Other sites include palm, wrist, forearm, foot and tip of the spine.

Rarely, the tumour may occur in the gastrointestinal tract (stomach, small intestine, colon), trachea, lungs, mesentery, bone, vagina and the cervix.

A glomus tumour is rare in the sinonasal region. 

Almost all cases of sinonasal glomus tumor are benign and are usually cured by complete excision.

Cutaneous lesion usually occurs in adults (20- 40 years) and presents as small blue red nodule in the deep dermis or subcutis.

Intravascular spread of the glomus tumour is rare and has been described in the stomach and subcutaneous tissue.

Most frequent location is the forearm.

The pathologist must be aware of this variant of glomus tumour to avoid misdiagnosis and unnecessary additional treatments.

Glomus tumour proper (solid glomus tumour):

Solitary painful lesion.

Microscopic features:  Histologically, this is a well circumscribed lesion characterized by solid aggregates of glomus cells around small capillary sized vessels in a myxoid or hyalinized stroma.

The glomus cell is round, regular shaped with a sharply punched out rounded nucleus.

Rare variants:

I. Epithelioid:    Unlike conventional glomus tumors, which consist of small polygonal cells with dark round nuclei and scanty cytoplasm, the epithelioid lesions are composed of large polygonal to spindle-shaped cells with abundant eosinophilic cytoplasm and large, irregularly shaped nuclei.

The cells have both epithelioid and myoid qualities. 

Differential diagnosis:   Spindle-cell lesions, such as  schwannoma , leiomyoma, hemangiopericytoma.

II. Oncocytic:
             
Glomangioma-    

Three different clinical variants of glomangioma have been recognized: solitary, multiple, and nodular, or plaquelike.

Glomangiomas are usually painless.

These are mostly noted in adolescence and is less common than glomus tumour proper.

Microscopic features:  Histologically, these are poorly circumscribed, unencapsulated lesions characterized by prominent ectatic vessels and less conspicuous glomus cells.

Secondary thrombosis and phlebolith formation may occur.

The features resemble those of cavernous hemangioma.

Glomangiomyoma-    

Overall features are similar to glomus tumour and glomangioma.

There is gradual transition from round glomus cells to elongated smooth muscle cells.

These features are more obvious near large blood vessels.

 Atypical and Malignant Glomus Tumour:

I Classification of unusual glomus tumours: (Gould et al)

1. Locally infiltrative glomus tumour; 

2. Cytologically malignant tumour arising and merging with typical glomus tumour (glomangiosarcoma arising in a benign glomus tumour). 

3. De novo glomagiosarcoma

Glomangiosarcoma-  Patient with glomangiosarcoma usually developed widespread metastases.

Microscopic features: Histologically, the features are those of benign glomus tumour  with sarcomatous areas consisting of short spindle cells with hyperchromatic nucleus (round cell or leiomyosarcomatous appearance) and prominent mitotic figures.

II Classification of atypical glomus tumours: (Folpe et al.)

1. Malignant ; 2. Symplastic ; 3. Glomus tumors of uncertain malignant potential, and 4. Glomangiomatosis

Atypical glomus tumour: Glomus tumours display unusual features, such as large size, deep location, infiltrative growth, mitotic activity, nuclear pleomorphism, and necrosis.

Atypical features are usually observed centrally with a rim of benign-appearing glomus tumour.

Malignant glomus tumour:   Tumour with a deep location and a size of more than 2 cm, or atypical mitotic figures, or moderate to high nuclear grade and 5 mitotic figures or more/50 HPF.

High nuclear grade alone, infiltrative growth, and vascular space involvement are not associated with metastasis.

Symplastic:  High nuclear grade in the absence other malignant features.

Glomus tumour of uncertain malignant potential:   Tumours that lack criteria for malignant glomus tumour or symplastic glomus tumour but have high mitotic activity and superficial location only or large size only or deep location only.

Glomangiomatosis: Tumours with histologic features of diffuse angiomatosis and excess glomus cells.

Immunohistochemistry:  

The tumour cells reveal immunopositivity for vimentin, smooth muscle actin and muscle specific actin in the cytoplasm. The cells do not stain with endothelial markers. Desmin is occasionally only focally positive.

Differential diagnosis:Glomuvenous malformation (glomangioma) and venous malformation (Glomuvenous malformation (glomangioma) and venous malformation: distinct clinicopathologic and genetic entities. Arch Dermatol. 2004;140(8):971-6.)

Adnexal tumour- Eccrine spiradenoma (two population of cells and focal ductal differentiation);  Hemangiopericytoma (spindle shaped cells and branching staghorn  vessels); Intradermal naevus with pseudovascular spaces (focal nesting, S100 positive and evidence  of maturation) ; Rhabdomyosarcoma; Ewing's sarcoma/PNET ; Hidradenoma ; Leiomyosarcoma with epithelioid change.

Note: Recent molecular studies have identified microRNA 143-NOTCH fusions or NOTCH1-3 rearrangements in benign and malignant glomus tumors. Novel MIR143-NOTCH fusions in benign and malignant glomus tumors. Genes Chromosomes Cancer. 2013;52:1075–87.  

Dermatopathology Quiz Case 144

Benign glomus tumor of the superior posterior mediastinum.

Infiltrative glomus tumor arising from a benign glomus tumor: a distinctive immunohistochemical pattern in the infiltrative component.

Congenital multiple plaque-like glomangiomyoma.

Glomangiosarcoma of the hip: report of a highly aggressive tumour with widespread distant metastases.

Myofibromatosis in adults, glomangiopericytoma, and myopericytoma: a spectrum of tumors showing perivascular myoid differentiation.

Malignant glomus tumor: a case report and review of the literature.

Malignant glomus tumor. A case report of widespread metastases in a patient with multiple glomus body hamartomas.

Epithelioid glomus tumor.

Glomus tumor. A histological, histochemical and immunohistochemical study of the various types.

The immunophenotype of hemangiopericytomas and glomus tumors, with special reference to muscle protein expression: an immunohistochemical study and review of the literature.

Intermediate filament proteins and actin isoforms as markers for soft-tissue tumor differentiation and origin. III. Hemangiopericytomas and glomus tumors.

Malignant glomus tumor: a case report and review of literature, focusing on its clinicopathologic features and immunohistochemical profile.