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11

Diagnostic Approach to Neoplastic Conditions Causing
Lameness

Bernard Séguin

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Flint Animal Cancer Center,
Colorado State University, Fort Collins, CO, USA

11.1 Introduction

Neoplasia is a frequent cause of lameness and therefore must be considered as a differential diagnosis
for most patients. Signalment, history, and physical exam may raise suspicion of a neoplastic con-
dition. Neoplasia is a common differential diagnosis in certain breeds and older patients, although
osteosarcoma can affect any breed and is known to affect younger animals as well (Liptak et al.
2004). Certain histories can raise the suspicion of a neoplastic condition, such as one that indicates
a pathologic fracture (e.g. progressive thoracic limb lameness followed by a nontraumatic event
that causes acute non‐weight‐bearing lameness). A general approach to the patient with neoplasia
causing lameness is outlined in Figure 11.1.

11.2 Diagnostic Methods

11.2.1 Physical Examination
Lameness is a common finding with tumors but it may not always be present. Given the paucity of
soft tissues around the lower limb, it is common to visualize a “swelling” or mass effect if tumors
affect these regions. Soft tissue masses should be assessed for their ability to be freely movable, to
determine their origin (skin versus subcutaneous tissue versus deeper soft tissues or bone) and
adherence to the underlying bone. Palpation of the soft tissues or bones affected by cancer gener-
ally is painful, and frequently a mass effect may be observed (Figure 13.13). With osseous neopla-
sia, pain can be elicited when direct pressure is placed on the bone, while arthropathies cause pain
during end range of motion. Tendinopathies can be diagnosed by isolating the muscle and stretch-
ing it (Chapter 5). Physical exam findings should always be confirmed with diagnostic imaging.

11.2.2 Fine-needle Aspirate and Biopsy

In order to diagnose neoplasm, a fine‐needle aspirate (FNA; which leads to cytology) or biopsy
(which leads to histopathology) is required. If a nondiagnostic sample or reactive tissue is obtained

Canine Lameness, First Edition. Edited by Felix Michael Duerr.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/duerr/lameness