Bite-size introduction to canine hematologic malignancies

Abstract

Hematologic malignancies are frequently diagnosed in dogs and result in a spectrum of clinical signs associated with specific disease types. The most frequently encountered hematologic tumors in dogs include lymphoma, lymphoid and myeloid leukemias, and mast cell, plasma cell, and histiocytic neoplasias. Coupled with the heterogeneous presentations of the different categories and subtypes of canine hematologic malignancies, outcomes for these tumors are also variable. Considering this, appropriate treatment options range from active surveillance to curative intent approaches harnessing surgical, chemotherapeutic, and radiation-based modalities. The underlying pathology of many of these diseases bears remarkable resemblance to that of the corresponding diagnosis made in human patients. We introduce some of the pathogenic drivers of canine hematologic cancers alongside their clinical presentations. An overview of standard-of-care therapies for each of these diseases is also provided. As comparative oncology gains recognition as a valuable setting in which to investigate the pathogenesis of neoplasia and provide powerful, clinically relevant, immunocompetent models for the evaluation of novel therapies, the number of clinicians and scientists participating in cancer research involving dogs is expected to increase. This review aims at providing an introductory overview of canine hematologic malignancies.

Figure 1.

Wide surgical excision of a degranulating canine cutaneous MCT. (A) Preoperative photograph after initial surgical preparation and planning for wide excision. (B) Intraoperative photograph after wide resection of the tumor and elevation of a subdermal plexus skin fold flap. (C) Postoperative photograph revealing skin closure using a subdermal plexus flap. Images provided by Maureen Griffin and Ingrid Balsa.

Figure 2.

Metastatic gastric EMP in a 10-year-old female neutered cross-breed dog. Cytologic smear of fine-needle aspirate taken from a mesenteric lymph node revealing a pleomorphic population of malignant round cells with erythrocytes and neutrophils noted in the background (modified Wright-Giemsa stain; ×40 objective). Reprinted with permission.

Figure 3.

Splenic HS in a 10-year-old female neutered cross-breed dog. (A) Ultrasonographic still of a large (maximum diameter, 59 mm) well-vascularized (as demonstrated by Doppler color flow) mass lesion of mixed echogenicity within the tail of the spleen. (B) Histopathology of the splenic mass revealed a poorly encapsulated neoplasm showing both round and spindle morphologies of large tumor cells forming sheets and streams. Diagnosis of HS was confirmed using immunohistochemical stains (not shown; hematoxylin and eosin stain; ×20 objective).