IMAGING FINDINGS IN HORSES WITH PHARYNGEAL SQUAMOUS CELL CARCINOMA

Introduction
Squamous cell carcinoma (SCC) has been occasionally reported in the equine pharyngeal region1-3. The aim of this poster is to describe imaging findings in 4 cases of pharyngeal SCC.
Material and methods
Four old horses, mean age 19.5, 2 females and 2 geldings, were referred for dyspnea (3/4) and/or dysphagia (3/4). Because of dyspnea radiographs were realized prior to endoscopy. Ultrasound (US) was performed in all cases by ventral and lateral approach using a linear 7,5MHz transducer. A post-mortem computed tomography (CT) of the head was performed in one case (16 slices CT, Somatom 16, Siemens).
Results
Radiographic opacity of the pharyngeal region was increased in all cases. A soft tissue mass was also visible in the caudal maxillary sinus in 1 horse. The epiglottis was either not recognized or difficult to see with an abnormal shape. Pharyngoepiglottic distance and nasopharyngeal diameter were reduced in all cases. The soft palate was either thick or impossible to be outlined, with an irregular surface. In 1 case it was dorsally displaced. The dorsal pharyngeal wall looked unevenly thickened or impossible to be outlined ventrally due to border effacement. No bony damage was identified on radiographs. A hypoechoic heterogeneous mass was visualized at US in 2 cases and an enlargement of the mandibular lymph nodes was observed in 3 cases. Lymphnodes had also heterogeneous echogenicity and increased doppler signal in 1 case. Oral and pharyngeal endoscopic examination confirmed a pharyngeal mass in 2 cases but was unsuccessful or incomplete because of passage impairment in 2. CT revealed maxillary bone lysis in the horse with a mass in the maxillary sinus. Histopathological examination of local biopsies or necropsy revealed pharyngeal SCC invading epiglottis, pharyngeal wall and soft palate in the 4 horses and the maxillary sinus in one.
Discussion/Conclusion
Because endoscopy can be impaired by the size of the mass, radiology is helpful in estimating the extent and invasiveness of the process and US to confirm lymphadenopathy. However because of its relatively low sensitivity and the local increased opacity, radiographic examination may underestimate bone lysis.