chapter 33 Mast Cell Tumors.....................................
DEFINITION/OVERVIEW
Neoplasia arising from malignant round cells of hematopoietic origin.
Mast cell granules contain many substances including histamine, heparin, platelet-
activating factor, serine proteases, lysosomal enzymes, and cytokines.
ETIOLOGY/PATHOPHYSIOLOGY
Histamine and other vasoactive substances released from mast cell tumors may cause
erythema and edema; histamine may cause gastric and duodenal ulcers.
Heparin release: increases likelihood of bleeding.
Skin and subcutaneous tissue most common tumor sites in dogs.
Hemic/lymphatic/immune-spleen: common primary location in cats (up to 50% of
cases); rare in dogs; site of metastasis from the skin or subcutaneous tissue.
Gastrointestinal: intestinal mast cell tumor uncommon in cats and rare in dogs; gastric
and duodenal ulcers possible.
Etiology unknown: viral etiology suspected by some investigators; current emphasis
on genetic mutations of the tumor suppressor genep53(13.75–44.6% of tumors) and
c-KIT receptor tyrosine kinase.c-KIT mutations may result in increased recurrence and higher mortality; not all dogs
with mast cell tumors have mutations (15%); often positive for mutation in higher
grades of mast cell tumors (30–56%); measurement of c-KIT mutation by PCR may
be a useful prognostic indicator.Histopathologic grading system valuable in the dog, not valuable in the cat; prognos-
tication should rely on both histologic grading and clinical staging.
SIGNALMENT/HISTORY
Most common skin tumor in the dog: 17–21% of skin and subcutaneous tumors;
11–14% of cases may develop multiple tumors synchronously or successively.
Second most common skin tumor in cats (often benign in skin): 20% of skin tumors.
Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Dermatology, Third Edition.
Karen Helton Rhodes and Alexander H. Werner.
©2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc.
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