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History and Signalment

Signalment: 9 year old, Thoroughbred, Gelding

Referred for CT imaging with history of  approximately 4 month duration of left sided, sanguineous-to-mucoid discharge.


Transverse Skull CT - Bone Window without contrast

Transverse Skull CT - Soft Tissue Window without contrast

Transverse Skull CT - Soft Tissue Window with contrast

Imaging Reports

CT Findings:

  1. Filling the left caudal maxillary sinus, extending caudally to the left ethmoid labyrinth and the sphenopalatine sinus, there is a large homogeneously hyperattenuating mass that does not exhibit contrast enhancement. The mass causes moderate expansion of the caudal maxillary sinus and small multifocal regions of lysis of the left maxilla. The left rostral maxillary sinus is moderately expanded, medially displacing and causing mild multifocal lysis of the left infraorbital canal and mildly displacing the nasal septum to the right. The rostral maxillary sinus also contains a large volume of heterogeneously fluid and soft tissue attenuating (avg. 23 HU, range 6-43 HU), non-contrast enhancing material.
  2. The left maxillary third molar (311) has mild diffuse widening of the periodontal space and moderate, locally extensive lysis of the tooth root and alveolar bone, with a few small mineral fragments displaced dorsally within the adjacent ventral aspect of the left rostral maxillary sinus. The left maxillary first molar (309) has mild diffuse widening of the periodontal space, and mild, locally extensive lysis of the tooth root.
  3. The caudal aspect of the tongue contains a large (5.3 x 4.1 x 3.5 cm) well margined, pre-contrast hyperattenuating, non-contrast enhancing mass. The left and right parotid salivary glands and the left and right guttural pouches contain a few small, well margined pre-contrast hyperattenuating, variably, mildly contrast enhancing nodules. The soft tissues of the face contain many, small, randomly distributed, pre-contrast hyperattenuating, variably mildly contrast enhancing nodules.


  1. Large, left caudal maxillary sinus mass
  2. Left, rostral maxillary sinopathy
  3. Moderate to severe, perioendodontic disease, 309 & 311
  4. Multifocal, hyperattenuating nodules and mass


The clinical signs are attributed to findings (1,2).


Differential diagnoses for finding (1) include ethmoid hematoma and neoplasia (e.g. melanoma).

Differential diagnoses for finding (2) may represent sinusitis or mucus accumulation and is likely due to obstruction of the nasomaxillary aperture and perioendodontic disease.

Differentials diagnoses for finding (4) hyperattenuating nodules are prioritized to be melanomas.

Case Outcome

Surgery Report:

The patient was sedated, positioned in the stocks, and surgical sedation was maintained with a detomidine CRI. The left side and middle of the face over the maxillary and frontal sinuses were clipped and prepped using standard aseptic technique; a left maxillary nerve block was performed with 20ml bupivacaine. The skin was blocked in a line using carbocaine (40ml). A routine approach to the left frontal sinus was performed by creating an axially based bone flap. A skin incision was made using a #10 blade from medial to lateral halfway between the supraorbital foramen and the medial canthus. It was extended rostrally for 10 cm and then lateral to medial to create three edges of a rectangle. The subcutaneous tissue and periosteum were incised using the #10 blade and reflected away from the incision.

The frontal bone was noted to be thickened. The flap was created by transecting the 3 edges of the rectangle with an oscillating bone saw. A mallet and osteotomes of various sizes were used to gently elevate the flap.

Upon opening the flap, approximately 300 mLs of thick dark brown viscous discharge as well as yellow white mucopurulent discharge exuded from the sinus, revealing a large cyst-like lining structure adhered to, and displacing the sinonasal structures medially, and involving the infraorbital nerve.  This large structure was removed via blunt dissection as well as with use of ligasure (on the axial wall of the dorsal/ventral conchal sinus), with care to avoid damage to the infraorbital nerve.

The left sided sinuses were aggressively lavaged, and packed with Combat gauze and Kerlix gauze. The Fronto Nasal flap was temporarily closed with a mattress pattern using 0 monocryl to close the 3 corners and periosteal layers simultaneously and the skin was closed with staples. Gauze was placed over the surgical sites and held in place with Elastikon.


Morphologic Diagnosis:

  • Nasal cavity, mass: Fibrovascular polyp with hemorrhage, hemosiderin, hematoidin and mixed inflammatory infiltrates


  • Histologic findings of exuberant fibrovascular tissue with significant areas of chronic-active hemorrhage are consistent with ethmoid hematoma, with extensive areas of ulceration and inflammation. Although the pathogenesis of nasal polyps is unknown, the assumed to represent an aberrant visa proliferative response to submucosal hemorrhage. Although there is no evidence of any significant bacterial or fungal infection, additional histochemical stains would enable a more confident exclusion of pathogens in section; if desired, the stains are available for an additional fee. If this is desired, please contact the Anatomic Pathology office in writing either via fax to (607) 253-3357 or email to and quoting the accession number of the case (220069-19).

Histologic Description:

  • Left nasal cavity, mass (slides 1-5, 5 sections): In all examined sections the respiratory mucosa and submucosa is multifocally to focally extensively severely expanded by large swathes of fibroblasts and collagen fibers with perpendicularly oriented small caliber vessels (granulation tissue), and vast areas of hemorrhage, admixed with fibrin, macrophages laden with dark brown, granular pigment (hemosiderophages), and globules of bright yellow extracellular pigment (hematoidin; ceroid sequins). Multifocally infiltrating the fibrotic and hemorrhagic areas of mucosa and submucosa are large numbers of inflammatory cells; in some areas there is a predominance of aggregating eosinophils, or aggregating plasma cells, and in others mixed populations of neutrophils, macrophages, lymphocytes, plasma cells and eosinophils. Additionally, in one section there is a focally extensive region with dozens of large acicular clearings (cholesterol clefts).


  • Additional histochemical stains for bacteria and fungi do not reveal the presence of infectious agents; however, histochemical staining is a relatively insensitive method for detection of infectious agents, and a negative result does not rule out an infectious cause. Bacteriological culture might provide a more definitive diagnosis.

Relevant References