Glomus tumours in the skin and subcutis of three horses.

This research paper documents the occurrence of glomus tumours, a type of skin cancer, in three horses. The scientists diagnosed, analyzed the tumours microscopically and immunohistochemically, and concluded that two of them met the criteria for malignant tumours while the third horse was euthanized due to complications associated with treatment and recurrence of the tumour.

Clinical Presentation of Tumours

• The tumours were depicted as variably painful, nonulcerated masses located on the horses’ head or neck.
• The size of the tumours ranged from 0.4 to 9 cm in diameter.
• Upon examination, the tumours were found to involve deep dermis and subcutis or the subcutis and underlying skeletal muscle.
• The structures within the tumour included neoplastic epithelioid cells arranged in sheets, cords, and packets. These cells frequently formed nodular bulges into large vascular spaces, especially around the tumour periphery.
• In every case, large nerve branches were found connected with these tumours.

Microscopic Analysis

• Immunohistochemical analysis was used to classify the tumour cells. The tumour cells expressed α-smooth muscle actin and vimentin, proteins that are typically found in mammalian cells.
• The tumour cells from two out of the three cases also expressed desmin, which is another protein found in the cells of vertebrates.
• The researchers also found a laminin- or collagen IV-positive basement membrane around individual tumour cells or small groups of cells in all three cases, which supports being of mesenchymal origin, a feature common in glomus tumours.

Diagnosis

• Putting together the morphological appearance and protein expression, the researchers then subsequently diagnosed these tumours as glomus tumours, specifically referring to the solid type often found in human beings.
• Applying the human classification system, two of these tumours met criteria for being malignant, hence were classified as glomangiosarcomas.
• One of the horses had to be euthanized due to complications associated with the tumour’s recurrence and subsequent treatment-related necrosis and infection.