Fine-needle aspiration (FNA) can be useful for preliminary diagnosis of canine cutaneous masses. This diagnostic technique can provide preliminary information as to whether the population of cells are representative of inflammation (eg, abscess, inflammatory nodule) or neoplasia. Round cell tumors especially can be fairly exfoliative, which can allow for a reasonably rewarding aspiration of MCTs.2
One study has suggested that MCTs measuring >3 cm had a worse prognosis; thus, waiting until tumors are larger may affect prognosis.5 This may be secondary to the potential for the mass to become nonresectable with too much growth.
Although this tumor could be benign (eg, a lipoma), brachycephalic breeds are overrepresented for MCTs; thus MCT should be ruled out as a differential.6
Performing excisional biopsy without knowledge of tumor type is generally discouraged. There are exceptions to the approach (eg, if the tumor size is too small for incisional biopsy). If histopathologic findings indicate the mass is malignant, scar revision will involve more extensive surgery than removal of the mass with appropriate margins at the first excision. For scar revisions, the scar is treated like the primary tumor; and for a MCT, this would include 2-cm lateral margins and 1 fascial plane deep.7,8 It is also recommended to submit all resected tissue for histopathology, as biopsy samples may not be indicative of the tumor as a whole. Tumors are heterogeneous and submission of the entire tissue may yield additional information.9 When the cost of the pathologist’s report is built into the cost of surgery, owners are not required to decide whether to obtain this information (ie, as they may not full understand its value).
Based on a history of no change in size for several months, this mass is unlikely an abscess; lancing the mass likely would not be diagnostic or otherwise beneficial to the patient and could hasten the spread of any neoplastic cells that may be present.