Page 179 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

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Biopsy and Sentinel Lymph Node

Mapping Principles

NICOLE P. EHRHART

A biopsy refers to a procedure that involves obtaining a tissue extensive surgery. All of these sequelae compromise the optimum
specimen for microscopic (i.e., histopathologic) analysis to estab- treatment pathway for the patient and will involve more morbid-
lish a precise diagnosis. Histopathologic interpretation of tissue ity and expense than a properly performed first excision. The issue
removed from a tumor is not foolproof and is highly dependent to be determined before surgery then is: how aggressive should the
on the quality of the biopsy sample submitted. Therefore it is surgery to remove the tumor be? It is intuitive that wide, ablative
important to understand basic principles of biopsy procurement surgery (e.g., body wall resection) would be inappropriate for a
and submission to obtain an accurate diagnosis. If the tissue diag- simple lipoma. It also follows that marginal excision (shell out) is
nosis is incorrect, every subsequent step in the treatment of the inappropriate for definitive treatment of an aggressive infiltrative
patient may also be incorrect. tumor such as a soft tissue sarcoma. Thus thorough knowledge of
Fine-needle aspiration cytology (FNAC) is a simple and rapid the tumor type is imperative before attempting surgical excision.
way to obtain information about a tumor and is often the first The best way to obtain this information is often via biopsy.
step in the diagnostic workup. Results of FNAC help guide the Specific indications for pretreatment biopsy are as follows:
diagnostic tests for staging. Studies have shown that FNAC is a 1. When FNAC is nondiagnostic or equivocal
reliable and useful method to guide further workup when neo- 2. When the type of recommended treatment (radiation, chemo-
1,2
plasia is suspected or to rule out neoplasia. Nonetheless, FNAC therapy, surgery) would be altered by knowledge of the tumor
gives limited information and may be nondiagnostic or equivocal. type or grade
Inflammation, necrosis, and hemorrhage may result in cytopa- 3. When the extent of recommended treatment (ablative surgery,
thologic changes that do not accurately represent the underlying wide excision, marginal excision) would be altered by knowl-
disease process. Histologic confirmation may be necessary for edge of the tumor type or grade
definitive diagnosis of neoplasia. 4. When the tumor is in a difficult area to reconstruct (maxillec-
There are many available techniques for obtaining tissue speci- tomy, locations requiring extensive flaps, head and neck, etc.)
mens, ranging from needle-core techniques to complete surgi- and planning is needed to prepare the patient and client appro-
cal excision. The choice of technique depends on the anatomic priately
location of the tumor, the overall health of the patient, suspected 5. When knowledge of the tumor type or histologic grade would
tumor type, and clinician preference. Biopsy techniques can be change the willingness of the client to proceed with curative-
grouped under one of two major categories: pretreatment biopsy intent treatment
(e.g., needle-core biopsy, punch biopsy, wedge biopsy, etc.) or If any one of the listed criteria is met, a pretreatment biopsy
excisional biopsy. Pretreatment biopsy is performed to obtain should be pursued.
additional information about the tumor before definitive treat- There are occasions when pretreatment biopsy would be con-
ment. Posttreatment (i.e., excisional) biopsy refers to the process traindicated. These include cases when the type of treatment or
of obtaining histopathologic information after surgical removal extent of surgery would not be changed by knowing the tumor
of the tumor. Excisional biopsy is best used to obtain a more type (e.g., testicular mass, solitary splenic mass) or when the surgi-
complete picture of the disease process (e.g., histologic grade, cal procedure to obtain the biopsy is as risky as definitive removal
histologic subtype, degree of invasion into regional vasculature (e.g., spinal cord biopsy). In these cases, the patient would best be
and lymphatics, etc.) and provides an opportunity to evaluate served by excisional biopsy of the tumor if staging results support
completeness of excision. It is rarely ever the best first step in this choice.
obtaining a tissue diagnosis. Although excisional biopsy is attrac-
tive to many clinicians because it allows for definitive treatment Biopsy Methods
and diagnosis in one step, it is often used inappropriately in the
management of a cancer patient, resulting in incomplete surgical The more commonly used methods of tissue procurement are
margins. Incomplete surgical margins can result in local tumor needle-core biopsy, punch biopsy, incisional (wedge) biopsy, and
recurrence and the need for radiation therapy or a wider, more excisional biopsy.

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