Page 187 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

166 PART III Therapeutic Modalities for the Cancer Patient

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D
• Fig. 10.1, cont’d (C) Wide resection of tumor involves adequate lateral and deep margins. The width of
lateral margins is determined by the tumor type and ranges from 1 cm for benign tumors and carcinomas
to 3 cm for soft tissue sarcomas and up to 5 cm for vaccine-associated sarcomas. Malignant tumors may
have satellite tumor cells outside the tumor pseudocapsule (arrow). Deep margins are not determined by
depth but, rather, by tumor-resistant fascial layers. A minimum of one fascial layer should be included in
the resection. The deep margin is the most common site of failure. Dotted lines show the dissection planes
for marginal (A) and wide (B) excisions. Note how a marginal dissection in this example leads to residual
tumor cells in the surgical field. (D) Planned marginal resection of a soft tissue sarcoma on the distal limb of
a dog. Marginal resection results in removal of the measurable tumor burden, but microscopic tumor cells
may remain in the surgical wound. (A Photo courtesy of Dr. Paolo Buracco, University of Torino. D from
Johnston SA, Tobias KM: Veterinary surgery: small animal, ed 2, St Louis, 2018, Elsevier.)

ultrasonography have been used routinely for many years, and the adjacent tissues, and multiplanar views and three-dimensional
increased availability of computed tomography (CT) and mag- (3D) reconstructions can be manipulated at a computer worksta-
netic resonance imaging (MRI) has added greatly to our ability to tion to help the surgeon envision a surgical plan before the time of
determine the extent of a solid tumor and optimize the surgical surgery with complicated cases (e.g., large skull tumors). Further-
approach. CT is now readily available at most specialty hospitals more, for more complex surgeries, CT images can be used to print
and allows good visualization of neoplastic tissue (particularly 3D models to further assist the surgeon in preoperative planning
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when it enhances well with an intravenously administered con- and intraoperative decision making. MRI is preferred for tumors
trast agent), adjacent muscle bellies and fascial planes, intraab- of the central and peripheral nervous system and perhaps tumors
dominal and intrathoracic organs, regional lymph nodes (LNs), of the intraabdominal organs and cutaneous and subcutaneous
and bone (Fig. 10.2). CT is commonly used for imaging thoracic tissues. MRI is useful for determining the proximity of tumors
wall tumors to determine which ribs need to be resected, oral to important neurovascular structures and for assessing soft tissue
tumors to assess the degree of bone involvement, adrenal tumors components and intramedullary involvement of canine osteosar-
to assess caudal vena caval or renal involvement, and cutaneous coma before limb-sparing surgery is performed.
or subcutaneous masses to better assess local tumor invasion and Advanced imaging has greatly enhanced the surgeon’s abil-
extent of disease. Reconstructed CT images allow the surgeon to ity to assess the anatomic location and extent of various cancers;
choose the orientation in which to visualize a mass in relation to however, imaging needs to be interpreted in conjunction with