Page 1317 - Small Animal Internal Medicine, 6th Edition

CHAPTER 78 Approach to the Patient With a Mass 1289

requires general anesthesia and is more expensive. Plain
radiographs of the affected area may also be indicated to look
VetBooks.ir for soft tissue and bone involvement. Abdominal ultrasonog-
raphy or CT may be indicated for further staging in patients
with certain neoplasms (e.g., hemangiosarcoma, intestinal
neoplasms, mast cell tumors). A minimum database con-
sisting of a CBC, serum biochemistry profile, and urinalysis
may provide additional clinical information (e.g., paraneo-
plastic syndromes, concurrent organ failure), and assess the
general health of the patient in preparation for potential
treatment.
If the mass is malignant and there is no evidence of meta-
static disease, surgical excision is usually recommended. If
there are systemic or metastatic lesions, the pathologist feels
comfortable with the cytologic diagnosis, and the tumor is A
likely to respond to chemotherapy (e.g., lymphoma, heman-
giosarcoma), chemotherapy constitutes the best viable option
(see Chapter 75). However, as discussed in Chapter 75, surgi-
cal resection of the primary mass (e.g., mammary carci-
noma) in a patient with metastatic lesions may provide
considerable palliation and prolong good-quality survival. If
an assertive diagnosis cannot be made on the basis of the
cytologic findings, an incisional or excisional biopsy of the
mass is advisable. The authors’ clinics almost never recom-
mend euthanasia in dogs and cats with metastatic lesions
and good quality of life because survival times in excess of 6
months (without chemotherapy) are common in animals
with most metastatic neoplasms. Metronomic chemotherapy
may result in long-standing stable or slowly progressive
metastatic disease (Fig. 78.1).
B L

APPROACH TO THE PATIENT WITH FIG 78.1
METASTATIC LESIONS Thoracic radiographs in a 10-year-old, mixed-breed dog
with a nonresectable thyroid carcinoma before (A) and
Radiographic or ultrasonographic evidence of metastatic after 756 days of metronomic chemotherapy (B).
cancer is occasionally found during the routine evaluation
of an animal with a suspected or confirmed malignancy, or A cytologic diagnosis of metastatic lung lesions can
during the evaluation of a cat or dog with obscure clinical usually be obtained through blind or ultrasonography-, fluo-
signs. In such instances, the clinician should be familiar with roscopy-, or CT-guided percutaneous FNA of the lungs. To
both the biologic behavior of the common neoplasms and do this, the area to be aspirated (i.e., the one with the highest
with their characteristic radiographic and ultrasonographic density of lesions radiographically or the easily identified
patterns (Table 78.1). Suter et al. (1974) described the typical and accessible lesions) is clipped and aseptically prepared.
radiographic appearances of various metastatic malignan- For blind percutaneous lung aspirates, the patient should be
cies. In addition, the owner should be questioned regarding in sternal recumbency or standing; a 25- or 27-gauge, 2- to
any prior surgeries in the pet (e.g., excision of a mass that 3-inch (5- to 7.5-cm) needle (depending on the size of the
was thought to be benign but may have been the primary animal) coupled to a 12- to 20-mL syringe is rapidly advanced
malignancy). through an intercostal space along the cranial border of the
If a cytologic or histopathologic diagnosis of malignancy rib to the depth required (previously determined on the basis
has already been made and the metastatic lesions are detected of the radiographs), and suction is applied two or three times
while staging the patient, treatment options can be discussed and then released; the needle is then withdrawn. Smears are
with the owner at this point (assuming that the metastatic made as described in Chapter 74. When aspirating lungs, the
lesions have arisen from the previously diagnosed primary clinician is likely to obtain a fair amount of air or blood (or
tumor). As a general rule, cytologic or histopathologic evalu- both) in the syringe. Rare complications associated with this
ation of one or more of these lesions should be performed technique include pneumothorax (patients should be closely
so that the clinician can best advise the owner as to the observed for 2-6 hours after the procedure and dealt with
appropriate course of action. accordingly if pneumothorax develops) and bleeding. As a