Page 156 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Mesenchymal Tumours and Other Neoplasms

143
Haemangioma
VetBooks.ir Benign tumour arising from the vascular endothelium.

Clinical features
• Common neoplasm in dogs, accounting for 4.5% of all skin neoplasms; rare in cats,
with an estimated incidence of 1.5–2%.
• Cutaneous haemangioma is mostly observed in adult/old patients. Similar lesions
have also been described in young animals, but may represent vascular malformations
rather than a true neoplasm.
• Well-demarcated dermal or subcutaneous mass, often bright red to dark brown. It
may be cavitated, contain variable amounts of blood, and ulcerated.
• Haemangioma occurs at any anatomical site.
• Solar-induced form has been described in light-skinned, short-haired dog breeds and
cats. This is more often localized in glabrous skin areas and may be multiple.
• Generally it is a slow-growing process.
• Over-represented canine breeds: Airedale Terrier, Gordon Setter, Boxer, Soft-coated
Wheaten Terrier, Wire Fox Terrier, Golden Retriever, Old English Sheepdog, English
Springer Spaniel, German Shepherd Dog, Whippet, Bloodhound, Saluki and Pointer.

Cytological features
• Cellularity is generally low and fine-needle aspirate can be non-diagnostic.
• Background: heavily haemodiluted. Platelets are not commonly seen.
• Low numbers of endothelial cells and capillary structures might exfoliate. Endothelial cells
are spindle shaped, occasionally plump, and have oval, often folded nuclei.
• Macrophages can be present, often showing erythrophagia or containing haemosiderin
and/or haematoidin crystals, indicative of previous haemorrhage.
Variants
Several variants of haemangioma have been described in the literature and include cavernous, infiltra-
tive, capillary, arteriovenous, granulation tissue type, spindle-cell, epithelioid and solar-induced
forms. Differentiation is based on histopathology.

Differential diagnoses
• Iatrogenic haemorrhage
• Haematoma
• Vascular malformation
• Well-differentiated haemangiosarcoma

Pearls and Pitfalls
Cytological diagnosis can be difficult because of the marked haemodilution of the sample and
the relatively low numbers of neoplastic cells harvested. Histopathology is often needed for a
definitive diagnosis.