Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 133

Cutaneous MCT is the second most common feline skin tumor, after basal cell tumor (Litster and Sorenmo 2006; Melville et al. 2015). Feline cutaneous MCTs are most commonly located on the head and neck, followed by the trunk and extremities (Litster and Sorenmo 2006). Feline MCTs located on the head are less biologically active than in dogs. An increased breed incidence in Siamese cats for cutaneous MCT is reported compared to other breeds (Litster and Sorenmo 2006; Melville et al. 2015). Feline cutaneous MCTs have a benign biological behavior compared to canine cutaneous MCTs. The Patnaik histopathological grading scheme used for canine cutaneous MCTs is not prognostic in cats (Molander‐McCrary et al. 1998; Lepri et al. 2003).

There are two forms of feline cutaneous mast cell disease, mastocytic and the less common histiocytic. The histiocytic form occurs in cats younger than four years old and is usually characterized by multiple nonpruritic, firm, hairless, pink subcutaneous nodules. Histiocytic MCTs generally regress spontaneously.

Histologic classifications of feline cutaneous MCTs are well‐differentiated, poorly differentiated, or histiocytic. High mitotic activity (>4 mitoses/high‐powered field) is reported as a negative prognostic indicator for feline cutaneous MCT (Lepri et al. 2003; Johnson et al. 2002). A recently proposed grading system for feline cutaneous MCTs classified MCTs as high grade if there were >5 mitotic figures in 10 hpfs and at least 2 of the following criteria: tumor diameter >1.5 cm, irregular nuclear shape, and nucleolar prominence/chromatin clusters (Sabattini and Bettini 2019). Further prospective validation of this grading scheme is required.

Cats with cutaneous MCTs should be staged with an abdominal ultrasound to evaluate the spleen for evidence of MCTs that may be metastasizing to the cutaneous location.

The prognosis for feline cutaneous MCT with surgical resection is good, with a 16–36% local recurrence rate. Incomplete surgical excision is not associated with a higher rate of tumor recurrence in cats with cutaneous MCTs (Molander‐McCrary et al. 1998; Litster and Sorenmo 2006). Radiation therapy using strontium‐90 has recently been reported as an effective treatment for feline cutaneous MCT (Turrel et al. 2006).

A distinct visceral form of MCT, which affects the spleen without cutaneous involvement, exists in cats and carries a poor prognosis (Litster and Sorenmo 2006). Systemic signs of chronic vomiting, anorexia, and weight loss can be associated with this form of MCT disease. Splenectomy is the recommended treatment for splenic visceral MCT (Kraus et al. 2015) and is associated with improved survival time compared to no splenectomy (Evans et al. 2018). The role of adjuvant chemotherapy for feline splenic MCT is still to be determined. A form of intestinal mast cell tumor also exists in cats (Sabattini et al. 2016; Barrett 2018).