Glomus tumour

Epidemiology

Glomus tumours are mesenchymal tumours composed of modified smooth muscle cells representing a neoplastic counterpart of the perivascular glomus body. They are found across a wide a range from children to the elderly with a peak in young adults. The sex distribution is equal, apart from subungual glomus tumours which show a female predominance.

Clinical features

Most glomus tumours are small benign neoplasms of the dermis or subcutis, occuring most commonly in the distal extremities (subungula or lateral digits). They also rarely occur in the gastrointestinal tract, bone, nerve, mediastinum, lung³ and genitourinary tract.

Macroscopic appearances

Most are blue-red nodules, less than 1 cm in diameter.

Histopathology

The common glomus tumour is composed of capillary-sized vessels surrounded by collars of glomus cells. The glomus cells are round with a rounded nucleus. The cell outline is sharply defined, particularly with PAS or toluidine blue stains. Occasionally, abundant eosinophilic cytoplasm confers an "oncocytic" appearance. Intravascular growth and signet-ring cell change have been reported. glomangiomas show a transition form glomus cells with elongated smooth muscle cells.

It is proposed that glomus tumours be subdivided into:

• benign

• symplastic glomus tumour (glomus tumour with nuclear atypia but otherwise lacking criteria for malignancy: the atypia is probably a degenerative feature.)

  glomangiomatosis (angiomatosis with prominent glomus component but lacking criteria for malignancy).

  glomus tumour of uncertain malignant potential:

  • superficial location with high mitotic rate (5 mitoses / 50 HPF)

  • or large size

  • or deep location

• malignant glomus tumour (arising from a benign glomus tumour or de novo):

  • large size (> 2 cm) and deep location

  • or atypical mitotic figures

  • or marked atypia with mitotic activity (5 mitoses / 50 HPF)

Immunohistochemistry

Smooth muscle actin	40/401, 31/342
Desmin	2/321, 0/342
Calponin	5/111, 25/302
h-Caldesmon	7/121, 27/312
Collagen type IV (investing individual cells)	8/81, 31/342
Vimentin	14/141, 34/342
Laminin	30/332
Cytokeratin	0/341
Cytokeratin 18	0/342
S-100	0/341, 0/342
CD34	5/271, 31/342
CD117	0/302
chromogranin	0/302
synaptophysin	0/302
CD20	0/342
CD45 (LCA)	0/342
HMB-45	never

Ultrastructure

The features are those of smooth muscle cells.

Differential diagnosis of atypical glomus tumour

of skin:

• Merkel cell carcinoma: cytokeratin 20 positive¹.

• eccrine spiradenoma: cytokeratin positive, muscle-specific actin restricted to basal cells.

• solid forms of hidradenoma: cytokeratin positive and often CEA and EMA positive.

• naevi and melanoma: S-100 and HMB-45 positive¹.

• cutaneous extraosseous Ewing's sarcoma / PNET: negative for muscle-specific actin and Collagen type IV¹.

• neuroblastoma: positive for neurofilament, chromogranin and synaptophysin¹.

• of deep tissue:

  • haemangiopericytoma: mixture of spindled and epithelioid cells, staghorn vessels and indistinct cell borders; usually negative for muscle specific actin¹.

  • epithelioid leiomyosarcoma: the distinction is entire morphological¹.

  • rhabdomyosarcoma: far more likely to be desmin-positive and also express MyoD1 and myogenin¹.

  • extraosseous Ewing's sarcoma / PNET: negative for muscle-specific actin and Collagen type IV¹.

  • see gastrointestinal glomus tumours.

  • carcinoid tumour

Prognosis

The metastatic rate in those glomus tumours classified as malignant was 38% (8/21 cases, of whom 6 died).

References

¹AL. Folpe, JC. Fanburg–Smith, M Miettinen, SW. Weiss. Atypical and Malignant Glomus Tumors. Analysis of 52 Cases, With a Proposal for the Reclassification of Glomus Tumors. Am J Surg Pathol 2001;25:1-12.

²Miettinen, M., Paal, E., Lasota, J., Sobin, L. H. Gastrointestinal glomus tumors: a clinicopathologic, immunohistochemical, and molecular genetic study of 32 cases. Am J Surg Pathol 2002;26:301-311

³Gaertner EM, Steinberg DM, Huber M, et al. Pulmonary and mediastinal glomus tumors--report of five cases including a pulmonary glomangiosarcoma: a clinicopathologic study with literature review. Am J Surg Pathol 2000; 24:1105-14

FM Enzinger and SW Weiss, Soft tissue tumours, third edition.

This page last revised 1.5.2002.