This document discusses biopsy principles and abdominal tumors in veterinary medicine. It provides guidelines for obtaining biopsy samples, including using the proper technique to procure enough tissue for an accurate diagnosis without increasing the risk of metastasis. Needle biopsy, incisional biopsy, and excisional biopsy are described as common methods. The role of the pathologist in interpreting biopsy results and potential sources of error are also outlined. For abdominal tumors, the document recommends evaluations like radiographs and ultrasound prior to exploration. It states that solitary masses should be explored for diagnosis and possible treatment, while diffuse disease is rarely helped by surgery alone. Factors like tumor stage, site and grade will impact therapy and prognosis.

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Veterinary Quarterly
ISSN: 0165-2176 (Print) 1875-5941 (Online) Journal homepage: https://www.tandfonline.com/loi/tveq20
Biopsy Principles
S.J. Withrow
To cite this article: S.J. Withrow (1998) Biopsy Principles, Veterinary Quarterly, 20:sup1, S14-S15,
DOI: 10.1080/01652176.1998.10807385
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2. • SOFT TISSUE SURGERY & ONCOLOGY
BIOPSY PRINCIPLES
S.J. Withrow1
INTRODUCTION
One of the most important steps in the management of the
cancer patient is the procurement and interpretation ofan ac-
curate biopsy specimen. Not only will the biopsy afford a
diagnosis but it will help predict biologic behavior which
aids in determining the type and extent of treatment which
should be afforded.
The common goal with any biopsy technique is to procure
enough neoplastic tissue to establish an accurate diagnosis.
Which procedure to use will often be determined by your
goals for the case, site ofthe mass, equipment available, gen-
eral status of the patient and personal preference and expe-
rience. An accurate tissue diagnosis should be attained be-
fore treatment for the following two reasons:
1. If the type of treatment (surgery versus radiation versus
chemotherapy, etcetera) or the extent of treatment (con-
servative versus aggressive surgical resection) would be
altered by knowing the tumor type. A biopsy is particu-
larly important ifthe surgery is in a difficult location (e.g..
distal extremity, tail or head and neck) for reconstruction
or ifthe proposed procedure carries significant morbidity
(e.g., maxillectomy or amputation).
2. Ifthe owner's willingness to treat their pet would be alter-
ed by knowledge oftumor type and therefore prognosis. a
biopsy is desirable before major therapeutic intervention.
GENERAL GUIDELINES FOR TISSUE PROCUREMENT
AND FIXATION
1. The proper performance of an incisional or needle biopsy
does not increase the rate ofmetastasis. On the other hand.
cancer cells may be allowed to contaminate the tissues
surrounding the local mass, making resection more diffi-
cult. The biopsy site should be planned so that it may be
subsequently removed along with the entire mass.
2. Avoid biopsies that contain only ulcerated or inflamed tis-
sues.
3. Several samples from one mass are more likely to yield an
accurate diagnosis than a single sample.
4. Biopsies should not be obtained with electrocautery as it
tends to deform (autolysis or polarization) the cellular ar-
chitecture.
5. If evaluation of margins of excision are desired, it is best
if the surgeon marks the specimen (fine suture or indian
ink on questionable edges) or submits margins in a sepa-
rate container.
6. Tissue is generally fixed in 10% buffered neutral formalin
with one part tissue to 10 parts fixative.
7. Tissue should not be thicker than one centimeter or it will
not fix deeply. Large masses can be cut into appropriate
sized pieces and representative sections submitted or sli-
ced like a loaf of bread, leaving one edge intact, to allow
fixation. After fixation (2-3 days), tissue can be mailed
with a 1: 1ratio oftissue to formalin.
8. A detailed history should accompany all biopsy requests!!
1 Department of Clinical Sciences, College of Veterinary Medicine and Biomedical
Sciences, Colorado State University, Fort Collins, Colorado 80523. USA.
BIOPSY METHODS
The more commonly used methods oftissue procurement are
needle punch biopsy, incisional biopsy and excisional
biopsy.
Needle Punch Biopsy
This method utilizes various types of needle core instru-
ments (Franklin modified Vim-SilvermanRa or Tru-CutRb,
etcetera) to obtain tissue (1,2). These instruments procure a
piece oftissue that is about the size ofthe lead in a lead pen-
cil and 1to 1.5 em long. In spite ofthis small sample size, the
structural relationship of the tissue and tumor cells can usu-
ally be visualized by the pathologist. Except for highly infla-
med and necrotic cancers (especially in the oral cavity)
where incisional biopsy is preferred, most needle core biop-
sies can be done on an outpatient basis with local anesthesia
and only rarely sedation.
Needle core biopsies are fast, safe, easy, cheap and usually
can be performed as outpatient procedures. They are gener-
ally more accurate than cytology but not as accurate as inci-
sional or excisional biopsy.
lncisional Biopsy
Incisional biopsy is utilized when neither cytology nor
needle core biopsy has yielded diagnostic material. Addi-
tionally. it is preferred for ulcerated and necrotic lesions
since more tissue can be obtained. Ideally, a composite
biopsy of nonnal and abnormal tissue is obtained from a lo-
cation which will not compromise subsequent curative re-
section. Care should be taken not to widely open uninvolved
tissue planes which could become contaminated with re-
leased tumor cells.
Excisional Biopsy
This method is utilized when the treatment would not be al-
tered by knowledge oftumor type (e.g., 'benign' skin tumors,
solitary lung mass, splenic mass, etcetera). It is more fre-
quently performed than indicated but when used on properly
selected cases, it can be both diagnostic and therapeutic as
well as being cost effective.
INTERPRETATION OF RESULTS
The pathologist's job is to determine: 1) tumor versus no tu-
mor, 2) benign versus malignant, 3) histologic type, 4) grade
(if clinically relevant), and 5) margins (if excisional). Many
pitfalls can take place to render the end result inaccurate.
Potential errors can take place at any level ofdiagnosis and it
is up to the clinician in charge ofthe case to interpret the full
meaning of the biopsy result. As high as 10% of biopsy
results are inaccurate in a clinically significant sense. If the
biopsy result does not correlate with the clinical scenario,
several options are possible:
1. Call the pathologist and express your concern over the
biopsy result. This exchange of information should be
a Franklin Modified Vim-Silverman Needle. V. Mueller Co, Chicago. JL
b Tru-Cut biop;y needles, Travenol Labs Inc. Deerfield. IL
S14 THE VETERINARY QUARTERLY, VOL. 20, SUPPLEMENT 1, APRIL 1998

3. • SOFT TISSUE SURGERY & ONCOLOGY
helpful for both parties and not looked upon as an affront
to the pathologist's authority or expertise. It may lead to:
a. re-sectioning ofavailable tissue or paraffin blocks
b. special stains for certain possible tumor types (e.g., to-
luidine blue for mast cells)
c. a second opinion by another pathologist.
2. If the tumor is still present in the patient, and particularly
if widely varied options exist for therapy, a second (or
third) biopsy should be performed.
ABDOMINAL TUMORS
S.J. Withrow1
INTRODUCTION
Cancer within the abdomen involves a diffuse group ofbe-
nign and malignant cancers affecting a diverse group ofor-
gans and systems. Patients may present with a variety of
signs and symptoms depending on the organ involved,
stage of disease and possible secondary or paraneoplastic
syndromes.
Specific evaluations prior to definitive treatment will vary
widely depending on each individual case and the owner's
wishes for treatment. 'Standard' work-up includes a CBC,
biochemical profile, urinalysis, abdominocentesis if free
fluid, and chest and abdominal radiographs. The wide-
spread use of ultrasound has revolutionized evaluation of
soft tissue structures within the abdomen. From a surge-
on's perspective, it is important to try to rule out lym-
phoma, which is the single most common disease not to
operate. Next in order is to try to decide if the lesion(s) is
solitary versus diffuse or metastatic. Opinions vary on
how much further workup is necessary prior to surgical ex-
ploration. In general, solitary masses within the abdomen
should be explored for diagnosis and hopefully therapy.
Diffuse disease is only rarely helped long term by surgery
but a definitive diagnosis can be attained and occasionally
palliation offered. Transabdominal fine needle aspirates
and needle core biopsies (guided by ultrasound) are gener-
ally reserved for suspect lymphoma or diffuse disease con-
ditions where one may be able to avoid surgery. Solitary
lesions are generally not aspirated or biopsied preoperati-
vely since surgery would generally be performed regard-
less ofthe diagnosis and there is a small but definite risk of
normal tissue contamination, rupture of the mass and he-
morrhage. Laparoscopy is another consideration in pre-
operative diagnostics but may take as long as an explora-
tory laparotomy and is not generally therapeutic. Many
other diagnostic studies can be performed including con-
I Department ofClinical Sciences, College of Veterinary Medicine and Biomedical
Sciences, Colorado State University, Fort Collins. Colorado 80523, USA.
A carefully performed, submitted and interpreted biopsy
may be the most important step in management and subse-
quent prognosis ofthe patient with cancer. All too often tu-
mors are not submitted for histologic evaluation after re-
moval because 'the owner didn't want to pay for it'.
Biopsies should not be an elective owner decision.
Because of increasing medicolegal concerns, it is not me-
dical curiosity alone that mandates knowledge of tumor
type.
trast studies (bowel and bladder), IVP's, venograms, an-
giograms, computed tomography and MRI.
Therapy and prognosis will vary markedly depend on the
stage, site and grade of the lesion. The patient should be
clipped liberally from the midthorax to the pubis and later-
ally at least halfway to the spine in order to allow a full ex-
ploratory and provide space for the possible exit offeeding
tubes, cystotomy catheters, etc. Patients should be blood
typed or crossmatched in anticipation of possible blood
loss. Electrocautery, vascular clips and stapling equipment
are routinely available if needed. Perioperative intrave-
nous antibiotics are given at induction and only continued
postoperatively if indicated. A fentanyl transdermal patch
is generally applied the day prior to surgery. It is desirable
to have a cytologist (cytology) or pathologist (frozen sec-
tion) available if intraoperative decisions on tumor type
(especially to rule out lymphoma) need to be made. A criti-
cal care unit for pain relief, maintenance fluids and ap-
propriate monitoring is ideal.
A full exploratory of the abdomen is important to detect
other occult disease. Draining lymph nodes from the pri-
mary tumor should be biopsied if detectable since lymph
node metastasis implies the need for adjuvant chemothe-
rapy, although few examples ofeffective chemotherapy in
the face of measurable metastasis exist. If postoperative
radiation is contemplated (e.g., transitional cell carci-
noma), the primary tumor and draining regional lymph
nodes should be marked with steel vascular clips to assist
in radiation planning.
Effective management of animals with intra-abdominal
cancer is often complicated by advanced stage disease at
presentation. Chemotherapy and radiation therapy have
only limited application (except for lymphoma). Large tu-
mor size, especially for apparent solitary lesions, is not a
contraindication to exploratory as these tumors are often
low grade in nature.
S15 THE VETERINARY QUARTERLY, VOL. 20, SUPPLEMENT 1, APRIL 1998