Page 514 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

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Tumors of the Respiratory System

SECTION A: CANCER OF THE NASAL PLANUM rhinoscopy are of limited value; however, swelling of the nasal pla-
num, occlusion of nasal passages, and increased opacity within the
rostral portion of the nasal cavity has been noted on radiographs.
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WILLIAM T.N. CULP Advanced imaging with computed tomography (CT) or magnetic
resonance imaging (MRI) is preferred, especially when tumors of
Anatomy the nasal planum are suspected to extend into the nasal cavity.
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These diagnostics are also useful in determining the presence of
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The nasal planum is considered the apical portion of the exter- bony invasion.
nal nose. This region is flattened, generally hairless, and includes
the nares and philtrum. The nasal planum is located rostrally to
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the nasal cartilages, which is a mobile group of seven cartilages Treatment
attached to the bony part of the nose via three ligaments (paired Surgery
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lateral nasal ligaments and a dorsal nasal ligament).
Nasal planum resection is the most commonly described and per-
Pathology, Behavior, and History formed technique for the management of dogs and cats with nasal
planum SCC. The nasal planum can be removed alone (Fig. 24.1)
The vast majority of the literature dedicated to nasal planum or in combination with the incisive or maxillary bones. The
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neoplasia has focused on squamous cell carcinoma (SCC). Other latter is indicated for tumor types where larger surgical margins
reported tumors of the nasal planum include fibrosarcoma, mela- are required for complete histologic excision, such as MCTs or
noma, mast cell tumor (MCT), osteosarcoma, and desmoplastic soft tissue sarcomas, or for tumors extending caudally beyond the
ameloblastoma. The biologic behavior of SCC of the nasal pla- nasal planum.
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num is similar to other locations in dogs and cats; these tumors The postoperative appearance after nasal planum resection can
rarely metastasize, but have the potential to be aggressive locally be challenging, especially for owners. A thorough discussion with
in some species. 3,4 an owner regarding the treatment options, postoperative function,
In general, SCC is a relatively common tumor in cats, but and postoperative cosmetic appearance is imperative to adequately
rare in dogs. These tumors are thought to be sunlight-induced prepare them for nasal planum resection, including the provision
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and may represent a malignant transformation from keratosis of images of the postoperative appearance of dogs postnasal pla-
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or carcinoma in situ to SCC; many cats (95% in one study ) num resection.
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are white or partially white in color. Labrador retrievers and The prognosis after nasal planum resection is generally good
golden retrievers may be overrepresented, accounting for 50% in dogs. Local recurrence was reported in two of six dogs treated
to 76% of cases in two studies. These tumors occur in older with surgery alone in one study, both with incomplete histologic
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dogs or cats, with ages at presentation generally greater than 10 excision. Seven dogs with more advanced tumors were treated
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3,4
years. with a combination of surgery and adjuvant radiation therapy
(RT), and all seven dogs had local tumor recurrence with a median
Diagnostic Evaluation time to recurrence of 9 weeks. Local recurrence was not reported
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in three dogs treated with combined nasal planum resection-
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Pretherapeutic evaluation of nasal planum tumors is important to incisivectomy and five of six dogs treated with combined nasal
direct diagnostics and eventual treatment. Although nasal planum planum resection-bilateral maxillectomy. 10
SCC has a characteristic gross appearance, fine-needle aspiration The prognosis is very good in cats after surgery. In one study of
(FNA) cytology and/or incisional biopsy should be considered to 61 cats with SCC, local tumor recurrence (Fig. 24.2) was reported
obtain a definitive diagnosis. in less than 10% of cats, with median disease-free intervals (DFIs)
The nasal planum should be imaged to determine the extent of 594 days and 426 days for cats with isolated nasal planum SCC
of disease, especially in dogs. Radiographs, ultrasound, and and SCC in multiple locations, respectively, when treated with
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