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- Can you ID equine sinonasal tumors on CT?
Cissell, Wisner, Textor, Mohr, Scrivani, Theon
Background
Sinonasal neoplasia constitutes 2–19% of equine sinonasal disorders and is associated with poor outcomes. Diagnosis of these neoplasms is challenging due to similarities with other sinonasal diseases and limitations of traditional diagnostic methods like radiography. Computed tomography (CT) offers superior diagnostic capabilities for assessing disease extent, features of malignancy, and prognosis. This study aimed to describe CT imaging features of equine sinonasal neoplasia and compare CT findings with skull radiographs.
Methods
A retrospective review of medical records from 1993 to 2008 identified 15 horses with sinonasal tumors diagnosed via CT and confirmed histologically. Tumor types included neuroendocrine tumors/neuroblastomas (n=5), sarcomas (n=5), carcinomas (n=3), myxoma (n=1), and ossifying fibroma (n=1). CT scans assessed tumor characteristics, bone involvement, and intracranial extension. Radiographs were available for 10 horses and compared with CT findings. CT features were evaluated using Hounsfield units (HU) and a semi-quantitative scale for tumor margins, heterogeneity, mineralization, and bone changes.
Results
Most tumors (14/15) were iso- or hypoattenuating relative to the masseter muscle, with heterogeneous soft tissue masses and destructive bone changes.
Thirteen tumors caused moderate to marked osteolysis of adjacent cortical bone, and 14 exhibited destructive changes of nasal turbinates, nasal septum, or infraorbital canal.
Intracranial extension was seen in 6 horses, most commonly through erosion of the cribriform plate.
Ossifying fibroma differed significantly, appearing as a hyperattenuating mass with extensive mineralization.
Radiographs detected sinonasal masses in all cases but were less sensitive than CT in identifying mass extent, sphenopalatine sinus involvement, and intracranial extension.
Neuroendocrine tumors/neuroblastomas were common (33%) and frequently involved the retrobulbar space, often extending into the cranial vault.
Limitations
The study was retrospective, limiting control over data consistency. Small sample size and variability in CT protocols (e.g., slice thickness) may have influenced the findings. Few cases involved contrast-enhanced CT, restricting evaluation of its utility.
Conclusions
CT provided detailed evaluation of sinonasal neoplasia in horses, surpassing radiography in identifying critical features like intracranial extension and aggressive osteolysis. These insights are essential for accurate diagnosis, treatment planning, and prognostic assessment. Radiographs remain a valuable initial screening tool but have notable limitations compared to CT. Further research should explore standardized CT protocols and the role of contrast-enhanced imaging in equine sinonasal disease.
FIG. 1. Transverse CT images of four different horses, each with a different tumor type of the nasal cavity and/or paranasal sinuses. The right side of each image represents the left side of the horse. Window width = 2000 HU and level = 200 HU. (A) Anaplastic sarcoma of the left nasal cavity, rostral and caudal maxillary sinuses, and conchofrontal sinus with suppurative sinusitis and osteomyelitis. (B) Myxosarcoma of both nasal cavities and all left paranasal sinuses. Note the expansion and multifocal osteolysis of the maxilla, loss of nasal turbinates, destruction of the left infraorbital canal and nasolacrimal duct, and irregular periosteal reaction of the left maxilla. (C) Undifferentiated carcinoma of the left ethmoid turbinates and conchofrontal sinus. (D) Neuroendocrine tumor/neuroblastoma originating from the left retrobulbar space and occupying the left conchofrontal and sphenopalatine sinuses. Note the osteolysis of the presphenoid bone creating a large defect in the left, ventral aspect of the calvarium.
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