Staging Cancer - How Much? When? Why?
Sarah E. Sheafor, DVM, DACVIM (Oncology)

Often when we are presented with a patient with a "lump" or "cancer," we have to decide not only how to obtain a definitive diagnosis, but also how to determine whether the cancer has appeared. Depending on the type and location of the tumor, different staging protocols are indicated. The first rule of thumb is not to perform any test whose results will not change the diagnosis, prognosis, or therapeutic plan.

Mammary tumors: In both dogs and cats, chest radiographs, assessment of regional lymph nodes via palpation, and aspiration or biopsy of any enlarged nodes, as well as a complete assessment of all other mammary tissue comprises the minimal evaluation of a patient with mammary cancer. CBC and profile will give any assessment of overall biopsies performed - they should be excised completely (wide margins) and biopsied. Inguinal lymph nodes should be removed at the same time as the caudal inguinal mammary gland, and should be biopsied. Axillary dissection, in the face of no palpable axillary lymph node enlargement, is probably not necessary.

Perianal tumors: These tumors are common in dogs and exceptionally rare in eats. Chest radiographs, abdominal ultrasound to assess sublumbar node status, and serum chemistry to assess calcium values are the essential components of a staging workup of a patient with a large, ulcerated, or invasive perianal mass or with any anal sac mass. Anal sac tumors metastasize early to the sublumbar lymph nodes. If any enlargement of these nodes is noted on abdominal ultrasound, they can be aspirated or a plan can be made to have these nodes removed at the time of the definitive surgery for the anal sac tumor.

Lymphoma (dogs): The complete staging workup includes a CBC, profile, lymph node biopsy, chest radiographs, abdominal ultrasound or radiographs to evaluate the liver and spleen, and a bone marrow aspirate. The stage of canine lymphoma, however, is very rarely of prognostic significance in dogs with multicentric lymphoma. The academic benefits of a staging workup must be balanced against the costs of this evaluation in a dog needing life-long chemotherapy. A modified staging protocol that is practical for the majority of dogs with multicentric lymphoma is a lymph node aspirate for diagnosis, and a CBC and profile to assess overall health, and to have a baseline for chemotherapy planning. Should significant abnormalities be noted on history, physical examination, or on the lab work, additional testing to rule out concurrent diseases or organ dysfunction may be needed.

Soft tissue sarcomas: Chest radiographs are the minimal essential components of a staging workup for dogs and cats with soft tissue tumors. For certain patients, radiographic imaging or CT scanning of the primary tumor is helpful in planning an appropriate treatment of aggressive surgery and/or radiation therapy. These studies are helpful in finding out how extensive and invasive the tumors is, and can sometimes change therapeutic recommendations.

Cutaneous mast cell tumors (dogs): The ideal staging workup for dogs with cutaneous mast cell tumors depends on the grade of the tumor, as well as the type of therapy recommended. In cases of an incompletely-resected, grade I or II mast cell tumor, where the owners are contemplating extensive surgery or radiation therapy, regional lymph node assessment, abdominal ultrasound, +/- splenic and hepatic aspirates, buffy coat smear, +/- bone marrow aspirate are performed to try to be certain that the tumor is confined to the primary site. In dogs with grade III mast cell tumors, metastatic disease is expected, so chemotherapy should be recommended in addition to local therapy. A complete staging workup is not as essential in these patients, although routine blood work and buffy coat smears can provide helpful monitoring points.

Visceral mast cell tumors (cats): Cats with splenic mast cell tumors often have positive buffy coat smears. Once the spleen is removed, the buffy coat can become negative. There is no difference in survival times between cats with positive or negative buffy coat smears prior to surgery, but it can provide a useful monitoring test.

Staging evaluations should be individualized to fit patient and client needs, as well as the type and location of the tumor. At SouthPaws Veterinary Referral Center, with our abilities to provide medical oncology and surgical oncology services, patients can be properly diagnosed and staged to ensure that they have the best outcome possible. With adequate staging and client education, we can make certain that clients are aware of the nature and prognosis of their pet’s cancer, and have been given the best integrative approach to therapy.

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