Mast Cell Tumors, Canine - contd.
The clinical signs of mast cell tumors in dogs are variable, and depend upon anatomic location. Tumors may originate in the dermis or in the subcutaneous tissues, and usually have overlying, intact skin, although ulceration can also occur. Palpation of these masses may produce Darier's sign, which is erythema, or redness, of the skin secondary to the release of histamine from the tumor. MCTs in dogs present as solitary or multiple masses. They are found primarily in the trunk, perineum, and extremities; and they are less common in the head and neck region. Variations in tumor size, even on a daily basis, are a relatively common historical sign in dogs with MCTs, as local swelling occurs and subsides. The affected area may be painful or sensitive to touch, especially if there is ulceration or marked swelling. Limbs may become swollen, with pitting edema, secondary to regional lymph node involvement and obstruction to venous and lymphatic fluid return from the tissues below.
Vomiting, diarrhea, poor appetite and weight loss may be noted in patients with systemic involvement. Stools may be melenic or darkened by the presence of digested blood, produced from gastrointestinal erosion or ulceration. Anaphylactic shock, with rapid heart rate, pale mucous membranes, weak pulses and collapse occurs in some patients that experience massive release of tumor substances into the blood stream.
