Oncology

Front 1

What is the role of surgery for the oncology patient?

Back 1

Varies based upon the patient and the type and behavior of the tumor.

Typically one or more of the following:
1) achieve a diagnosis,
2) stage the extent of
the tumor,
3) curative removal,
4) cytoreduction in
combination with therapeutic modalities,
5) palliation,
6) prophylactic / prevention - such as with
7) metastectomy, or
8) management of complications
resulting from other treatment modalities.

Front 2

What questions it is important to first ask when considering the role of surgery in attaining a
diagnosis?

Back 2

Will the type or extent of treatment be altered by
knowledge of the tumor type or its histologic grade?
Will knowledge of the tumor type change the owner’s
willingness to treat the pet? Does the location of the
tumor necessitate complicated reconstruction following
removal?

Remember, a tumor would be treated differently if it were a
well-differentiated mast cell tumor versus a poorly
differentiated mast cell tumor and if it were located on a
distal limb it might be treated differently still. If the answer
to these questions is yes, then it is best to perform a
biopsy to obtain a diagnosis prior to surgical treatment.
However, in some cases, there may be contraindications
to pretreatment biopsy e.g., brain or spinal cord masses,
bleeding splenic tumors.

Front 3

When attempting a complete excision, how much margin is needed?

Back 3

"Tumor should be excised
with a margin of normal tissue around it to ensure
complete removal of all neoplastic cells" Consider any
natural barriers to tumor extension, including fascialplanes, joints, tendon and nervous structures. A general guideline in veterinary medicine is a 2 cm margin. Wider margins are necessary in difficult to control tumors, e.g.
mast cell tumors, vaccine-site fibrosarcoma in cats.
Excision should extend at least 1 tissue plane deep to
deepest extent of tumor ie. tumor extends into
subcutaneous tissues then remove fascial plane below.
Areas with no fascial planes should have excision
minimum of 2 cm deep to tumor.

Front 4

Types of excision include:

Back 4

1) intracapsule resection which is used for benign
masses like lipomas,
2) marginal resection which involves dissection through the reactive zone while tumor and
pseudocapsule are removed en bloc, and
3) wide resection
which involves excision of pseudocapsule, reactive zone,
and margin of normal tissue. This is an intracompartmental
excision through normal tissue and is indicated
for well localized or low-grade malignant tumors. Skip
metastases could be left behind.
4) Radical resection
involves removal of the entire tissue compartment that
contains the tumor. Tumors should be treated as
"contaminated" tissue and contact with surrounding
"uncontaminated" tissue should be avoided. Body cavity
tumors should be packed off from the body cavity using
moistened laparotomy pads to prevent spread of tumor
cells to surrounding tissues. If omentum is adhered to the
tumor do not peel it off, instead resect attached omentum
with the tumor. Minimize manipulation of the tumor in
order to minimize tumor cell embolization and the release
of histamine from mast cell tumors. Always ligate the
vascular and lymphatic supplies to the tumor as soon as
possible to prevent tumor cell emboli. Avoid puncturing the
surface of the tumor or grasping it with forceps. Avoid any
free bleeding and use sharp dissection when possible.
The question of whether or not to lavage is up for debate.
Prior to closure, gloves, drapes, and instruments should
be changed as necessary to prevent contamination of
surgical site with tumor cells. Gentle handling of the tissue
is a necessity to avoid crushing the sample and creating
artifact.

Front 5

What is one of the most common presentations for a cancer patient in crisis?

Back 5

The acute abdomen: the difficulty is identification of the underlying
disease process. Multiple organ systems can result in an
acute presentation of abdominal pain. Because many of
these patients are presented in shock; elevated heart rate,
pale mucous membranes, capillary refill time prolonged,
resuscitative therapy should be instituted immediately.
Shock therapy should include fluid resuscitation with
intravenous crytalloids and synthetic colloids or blood
products to stabilize the patient. Monitoring trends in
systemic parameters including heart rate and blood
pressure is critical. Diagnostic procedures for the acute
abdomen patient should include attaining a minimum data
base including, if possible, a complete blood count, serum
chemistry profile and urinalysis. Specific procedures to
identify the underlying etiology include abdominal
radiographs, abdominocentesis, and abdominal
ultrasound. Abdominal radiographs may identify free air
within the abdomen, free fluid within the abdomen, or an
obstructive pattern within the gastrointestinal system.
Abdominocentesis is perhaps the most underutilized
procedure in the acute abdomen. In many instances this
procedure or the diagnostic peritoneal lavage yield the
highest benefit