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Skin Mass Removal

The most common skin tumours in dogs are mast cell tumours (MCT) (20%) and soft tissue sarcoma (15%).

Mast Cell Tumor (MCT)

MCT tumour s have different shapes; they can be on the skin (raised) or in the sub-cutis (under the skin), with or without hair, hard or soft on palpation.

Even small-sized tumours can release small granules containing inflammatory mediators, which cause extensive skin erythema (irritation/inflammation) around the tumour. This is called the Darier sign.

A breed predisposition is mentioned in scientific articles. The most affected breeds are Boxer, Boston Terrier, Pug, Bull Terrier, Bullmastiff, Cocker Spaniel, Staffordshire Bull Terrier, Fox Terrier, English Bulldog, Dachshund, Labrador Retriever, Golden Retriever, Beagle, Schnauzer, Chinese Shar-Pei, Rhodesian Ridgeback, and Australian Cattle dog (Shoop et al., 2015).

These types of tumors are frequently diagnosed with lab examination of samples collected through fine needle aspiration. Most of the time, this procedure does not require sedation; however, a skin biopsy under sedation and local anesthesias may be occasionally needed for a final diagnosis.

MCTs are divided into two main categories: low-grade and high-grade tumours. High-grade tumours are most likely to spread within the body through the lymphatic system.

Ideally, a full blood and urine test should be performed to reduce the anesthesias risks. Fine needle aspiration of lymph nodes, abdominal radiographs, and ultrasound should be performed to assess any internal spreading of the tumour. If internal metastatic lesions (spreading into the liver, spleen, or lymph-nodes) are suspected, samples collected by fine needle aspiration from both organs should be examined.

The surgical removal of the tumour can occasionally be challenging because of the anatomical position (e.g., limbs). Safe removal of the tumour would be achieved by removing 2-3 cm of skin margin around the mass margin and a deep plane tissue (e.g., the fascia). The choice of removal of 2-3 cm is based on lab results. Roots of high-grade tumours would often spread within 3 cm margins around the lump; based on this, 3 cm margins are often required for complete excision of the tumour.

Complete excision of the tumour and its roots will be confirmed through a lab examination called histopathology examination.

If a complete excision of the tumour is not achieved, a review surgery, radiotherapy, or chemotherapy may be required.

The skin is MCT in the leg of a dog. A 3 cm margin is measured with a sterile ruler and marked with a sterile pencil.

Soft Tissue Sarcoma (Skin)

Soft tissue sarcoma could arise from the skin or subcutaneous tissue. They are slow-growing and locally invasive tumours with a low metastatic rate (Tobias and Johnston, 2018). However, some high-grade tumours may spread through the hematogenous way (through blood vessels) within the lungs.

Fine needle examination could be used to rule out other types of tumours; however, this is not always diagnostic for soft tissue sarcoma. Ideally, the tumour should be examined through wedge/punch biopsy (histopathology). This often requires sedation and local anesthesias.

Blood and urine tests are always required to reduce general anesthesias risk.

Even though a CT scan is the gold standard for the diagnosis of lung metastasis, a chest radiographic examination would be always advised before the surgery is performed. Three views of the chest with inflated lungs would be sufficient for the diagnosis of lung masses bigger than 3 mm in diameter. Masses smaller than 3 mm in diameter can only be diagnosed by a CT scan exam.

2-3 cm margins around the tumour and one deep plane fascia are always recommended for complete excision of the tumour (Tobias and Johnston, 2018).

Complete excision of the tumour and its roots will be confirmed through a lab examination called histopathology examination.

In case of incomplete removal of the mass, a review surgery, radiotherapy, or chemotherapy may be required.


Shoop J.W., Marlow S., Church D.B., English K., McGreevy P.D, Stell A.J., Thomson P.C., O'Neill D.G. and Bridbeltz D.C. 2015, Prevalence and risk factors for mast cell tumors in dogs in England [Online]: [](

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