Page 1396 - Clinical Small Animal Internal Medicine

1334 Section 11 Oncologic Disease

Signalment Once a diagnosis of STS has been made, it is important
VetBooks.ir Soft tissue sarcomas tend to occur in middle‐aged to to determine the clinical stage or extent of disease.
Knowledge of the clinical stage will help determine the
appropriate treatment. Diagnostic tests that should be
older dogs and cats. No specific breed or sex predilection
has been identified but medium and large‐breed dogs performed prior to beginning definitive treatment
seem to be overrepresented. include three‐view thoracic radiographs, as the lungs are
the most common site of metastasis. Careful palpation of
regional lymph nodes with FNA or biopsy if accessible
History and Clinical Signs and/or abnormal. Careful palpation of the mass is neces-
sary to determine tumor size and fixation to surrounding
Soft tissue sarcomas present as firm, fixed, often slow‐ tissues. Advanced imaging with the use of computed
growing masses most commonly affecting the trunk, tomography (CT) or magnetic resonance imaging (MRI)
extremities, or oral cavity. Many times, they are initially can be helpful to evaluate the extent and invasiveness of
noted when they are small but go untreated as they are larger tumors, tumors in the head or neck, or tumors
assumed to be benign. The skin overlying these tumors within a body cavity.
is often moveable. When tumors are small, they are
nonpainful but as they grow, they invade into the tis-
sues which can result in the tumor becoming fixed or Therapy
ulcerated and infected. Clinical signs manifested from
the tumor are dependent on the site from which it Dogs
originates; for example, tumors on a limb may result
in lameness. Surgery
Local tumor control accomplished with wide, surgical
excision is considered the treatment of choice, and
Diagnosis advances in reconstructive techniques have significantly
expanded surgical options for aggressive resection with
A fine needle aspirate (FNA) is always warranted on good functional and cosmetic outcomes.
detection of any new mass or lesion. Cytology can be The surgical approach is classified according to the
beneficial in helping to rule out cysts or other tumor extent of the wound margins as intracapsular (when
types (mast cell tumors), but it is always important to the tumor is surgically penetrated); marginal (when the
keep in mind that cytology is not sufficient for a defini- tumor is excised just outside, or at, the pseudocapsule);
tive diagnosis of a STS. These tumors do not readily wide (when a portion of normal tissue is left around the
exfoliate and can contain areas of inflammation and tumor); and radical (when an entire anatomic segment is
necrosis. The presence of inflammatory cells and necro- removed, for example, amputation). The minimum rec-
sis in the absence of neoplastic cells on cytology does not ommended margins for gross surgical resection are 3 cm
rule out a STS. A study conducted on FNAs of 40 STSs lateral to the tumor and one fascial plane deep. However,
reported that only 62.5% of the cases yielded an accurate if the tumor is attached to the muscle or fascial layer, the
diagnosis, while 15% were incorrectly diagnosed. entire layer may be compromised and should not be
Biopsy and histopathology are needed for a definitive considered a clean margin. Additionally, adipose and
diagnosis of a STS. There are two types of tumor biopsy connective tissue are not tumor barriers. Biopsy tracts
commonly employed: pretreatment and posttreatment and any areas of fixation to surrounding tissue require
biopsy. Pretreatment biopsy is the preferred method and en bloc resection with the tumor, as these areas are con-
includes needle core (Tru‐Cut), wedge or incisional, and sidered contaminated.
punch biopsy. All biopsies should be positioned so that Soft tissue sarcomas are typically surrounded by a pseu-
the biopsy tract can be included in the curative intent docapsule, which allows the tumor to be “shelled out” and
treatment field. Posttreatment biopsy refers to an exci- submitted for histologic evaluation. Unfortunately, this
sional biopsy, where the diagnosis is made after removal type of marginal excision commonly results in tumor cells
of the gross tumor. Often, this method is attractive to pet extending to the edges of the resected tissue. Any surgical
owners as it allows for treatment and diagnosis in one procedure involving margins less than 3 cm and one
step but unfortunately, posttreatment biopsies are rarely fascial plane deep must be considered an incomplete
curative. An excisional biopsy should only be performed excision even if no macroscopic tumor is evident after
when it is possible to take a 2–3 cm margin around the removal.
tumor and even then it may not be necessary as lesions Histopathology of the tumor and surrounding tissue
may prove to be benign. following surgery is important as it provides surgical