Glomus Tumour

 

Epidemiology and Etiology:

    • Young adults typically

 

Common sites:

    • Skin or superficial soft tissues (almost always)
    • Distal extremities (vast majority)
      • Subungual particularly
      • Hand
      • Wrist
      • Foot
    • (GI sites):
      • stomach

 

Gross features:

    • small (<1cm) typically
    • red-blue cutaneous nodules
    • painful, particularly with exposure to cold or minor tactile stimulation
    • multiple in 10%
    • GI tract:
      • Circumscribed
      • Mural mass bulging either way
      • ulcerated
      • May be calcified

 

Histologic features:

    • Cells closely resemble the modified smooth muscle cells of the normal glomus body
      • Small
      • Uniform
      • Rounded
      • Central round nucleus
      • Amphophilic to lightly eosinophilic cytoplasm
      • Each cell surrounded by basal lamina (PAS / toluidine blue)
    • Typical glomus tumours:
      • Solid glomus tumour (75%)
        • Nests of glomus cells surrounding capillary sized vessels
        • Stroma may be hyalinized or myxoid
        • small cuffs of glomus cells often seen around small vessels located outside the main mass
      • Glomangioma (most common type when multiple or familial)
        • Dilated veins surrounded by small clusters of glomus cells
      • Glomangiomyoma
        • Transition from typical glomus cells to elongated cells resembling mature smooth muscle
        • May have a solid or glomangioma-like architecture
        • May have hemangiopericytoma-like vasculature (“glomangiopericytoma”)
    • May see:
      • Oncocytic change
      • Epithelioid change
    • GI tract:
      • Multinodular; nodules separated by strands of residual muscularis propria
      • Ulcerated
      • Sheets of cells surrounding gaping hemangiopericytoma-like vessels
      • Tumour cells present in muscular walls of larger vessels
      • Cells are round with sharply defined cell membranes
        • Perfectly rounded nuclei
        • Delicate chromatin
      • Not mitotically active
    • Glomangiomatosis:
    • Symplastic glomus tumour:
      • Striking nuclear atypia in absence of any other worrisome feature
    • Malignant glomus tumour (exceedingly rare):
      • Any one of the following:
        • Size >2cm and subfascial or visceral location
        • Atypical mitotic figures
        • Marked nuclear atypia and any level of mitotic activity
      • 2 types:
        • resembling leiomyosarcoma or fibrosarcoma
        • overall architectural similar to benign glomus tumour
      • necrosis is also worrisome
    • glomus tumour of uncertain malignant potential:
      • at least one atypical feature other than nuclear pleomorphism
      • not fulfilling above criteria for malignancy

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

 SMA

 

 

Calponin

 

 

h-caldesmon

 

 

Type IV collagen (pericellular, abundant)

 

 

Desmin (neg)

 

 

Laminin or collagen type IV (pericellular net-like pattern)

 

 

CD117 (neg)

 

 

Keratin (neg)

 

 

S100 (neg)

 

 

 

Molecular features:

    • familial multiple:
      • 1p21-22

 

Other features:

    • EM – modified smooth muscle cells
    • benign (vast majority)
    • GI tract lesions:
      • severe bleeding presenting with melena often
    • malignant glomus tumours are exceedingly rare (<1%)
    • association between subungual glomus tumours and NF1

 

References:

    • Gastrointestinal and Liver Pathology 2005
    • WHO Soft Tissue and Bone 2002