Canine Mast Cell Tumours

25% of malignant skin tumours. Average age - 8.5 years.

Can present from soft and lipomatous to hard and ulcerated.

Less than 25% are multiple on first presentation. Gastrointestinal signs (vomiting or melena) may also be seen. Bruising and erythema may be evident if the mass has been traumatized.

Work up requires:

Fine needle aspirate and haematology looking for possible bleeding signs.

Regional lymph node aspirate looking for sheets of mast cells

Mast cells in the front part of the body tend to metastasize to the sternal and hilar lymph nodes. Thoracic radiographs are rarely useful as it is rare to get true pulmonary metastases.

Abdominal radiographs are taken to look for organ and lymph node enlargement indicating possible extension to these sites.

Buffy coat smear, a low yield test but if positive it is very significant indication of systemic spread. In it we look for mast cells circulating in the blood.

Surgical removal should ideally involve 3cm margins and as deep as possible.

Histological analysis is required to aid in providing a prognosis for the client.

Clean margins to the removal site and no unfavourable signs > follow closely

Clean margins with unfavourable signs> Prednisolone +/- chemotherapy or radiation.

Dirty margins ie. signs it has spread beyond what was removed then we need to re-operate, +/or radiation, prednisolone and chemotherapy.

The worst thing to do if dirty margins is to wait and see.