Page 157 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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Haemangiosarcoma
VetBooks.ir Malignant tumour of vascular endothelium.

Clinical features
• Accounts for slightly less than 1% of cutaneous and subcutaneous tumours in dogs
and 2.8% in cats.
• Average age for cutaneous and subcutaneous haemangiosarcoma is 9–11 years in
both dogs and cats.
• Single, well-demarcated dermal or subcutaneous mass, often bright red to dark brown, soft
to firm; it may be cavitated, contain variable amounts of blood, and ulcerated. More aggres-
sive forms may present with poorly defined borders and may infiltrate adjacent tissues.
• Cutaneous and subcutaneous haemangiosarcoma in dogs may be solitary or part of a
multicentric syndrome involving internal organs (e.g. spleen, liver). In cats it may be
seen on the abdominal region, head (eyelid, pinnae), distal limbs and paws.
• A solar-induced form has been observed in both dogs (short-haired, light-skinned
breeds) and cats (white-haired males). It mostly occurs on glabrous skin areas.
• Cutaneous haemangiosarcomas are less aggressive than their visceral counterparts,
with lower metastatic potential and longer survival time.
• Histological location may have a prognostic significance in dogs, with dermal hae-
mangiosarcoma being associated with prolonged survival time when compared with
forms that invade the subcutaneous tissues or muscles.
• Over-represented canine breeds: short-haired, light-skinned dog breeds (e.g. Greyhound,
Whippet) and American Pit Bull Terrier.

Cytological features
• Cellularity is variable, often low.
• Background: heavily haemodiluted with large numbers of red blood cells; platelets are not
commonly seen.
• Aspirates are composed of variably but often large spindle-shaped mesenchymal cells. They
occur singly or in small aggregates.
• Nuclei are round to oval, medium to large. The chromatin is clumped or coarse. Nucleoli
may be multiple, prominent, round to irregularly shaped.
• The cytoplasm is moderate to abundant and variably basophilic. It is often elongated and
can contain small punctate clear vacuoles.
• Cells can exhibit erythrophagia and/or contain blue-black granules of haemosiderin.
• Anisokaryosis, anisocytosis and degree of pleomorphism are variable, often marked.
• Mitotic figures, including atypical forms, can be found.
• Low numbers of inflammatory cells, including macrophages containing red blood cells/
haemosiderin/haematoidin crystals may be observed.
• Haematopoietic precursors may occasionally be found (less commonly than in visceral
forms).