Page 1316 - Small Animal Internal Medicine, 6th Edition

1288 PART XII Oncology

CHAPTER 78
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Approach to the Patient

With a Mass

APPROACH TO THE CAT OR DOG WITH FNA. An intensive workup of a cat or dog with a solitary
A SOLITARY MASS mass (i.e., option 4) may not be warranted because addi-
tional diagnostic information regarding the mass is rarely
It is common for the practicing veterinarian to evaluate a gained from these procedures. However, the presence of
clinically healthy dog or cat in which a single mass is found metastatic lesions on thoracic radiographs may suggest that
during a routine physical examination or in which the owner the mass in question is a malignant tumor.
has detected a mass and is concerned about it. The mass can If a cytologic diagnosis of a benign neoplasm is made
be superficial (e.g., enlarged prescapular lymph node, dermal (e.g., lipoma), the clinician faces two options: to do nothing
mass, or subcutaneous mass) or deep (e.g., splenic mass, and observe the mass or surgically excise it. Because benign
enlarged mesenteric lymph node), and often the clinician neoplasms in cats and dogs are rarely premalignant (with the
wonders how to proceed and what to recommend to the notable exception of solar dermatitis/carcinoma in situ pre-
owner. ceding the development of squamous cell carcinomas), if a
In this situation, there are several possible approaches: benign neoplasm is definitively diagnosed, a sound approach
is to recommend a wait-and-see attitude. In those cases, the
1. Do nothing and see if the mass “goes away.” mass should be measured using calipers and recorded in the
2. Evaluate the mass cytologically. medical record; if the mass enlarges, becomes inflamed, or
3. Evaluate the mass histopathologically. ulcerates, then surgical excision is recommended. However,
4. Do a complete workup, including complete blood count the clinician should keep in mind that most benign neo-
(CBC), serum biochemistry profile, radiography, abdom- plasms are more easily excised when they are small (i.e., it is
inal ultrasonography, and urinalysis. not advisable to wait until the mass becomes quite large). To
some owners, the option of surgically excising the mass
The first option (i.e., do nothing and see if the mass goes shortly after diagnosis is more appealing; this can be sched-
away) is not really an option because the presence of any uled at the same time of a dental prophylaxis, for example.
mass is abnormal, and it should therefore be evaluated. As If a cytologic diagnosis of malignancy is obtained (or
a general rule, most masses, with the notable exception of if the findings are suggestive of or compatible with
inflammatory lesions, histiocytomas in young dogs, and malignancy), additional evaluation is warranted. Differ-
transmissible venereal tumors, do not regress spontaneously. ent approaches are indicated, depending on the cytologic
At our clinics, the typical first step in evaluating a solitary diagnosis (i.e., carcinoma versus sarcoma versus round cell
mass is to perform a fine-needle aspiration (FNA) to obtain tumor), the patient, the family, and the clinician. However,
material for cytologic evaluation (see Chapter 74). Using this with the exception of mast cell tumors (i.e., pulmonary
simple, relatively atraumatic, quick, and inexpensive proce- metastases are extremely rare in dogs and cats with this
dure, the clinician can arrive at a highly presumptive or tumor type), thoracic radiographs should be obtained to
definitive diagnosis in the vast majority of animals. After search for metastatic disease in dogs and cats with most
identifying the nature of the mass (i.e., benign neoplastic, types of malignant neoplasms. Two lateral views (i.e., right
malignant neoplastic, inflammatory, or hyperplastic), the and left) and a ventrodorsal (or dorsoventral) view are rec-
clinician can recommend additional tests to the owner. ommended to increase the likelihood of detecting metastatic
Performing a biopsy for histopathology constitutes lesions. If available, a computed tomography (CT) can detect
another valid alternative. However, the cost, the trauma to masses smaller than those detectable on plain radiography;
the patient, and the time it takes for the pathologist’s report however, this has not yet become a routine staging diagnos-
to become available make biopsy a less-attractive option than tic at the authors’ clinics due to the fact that this procedure

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