Pathology in Practice

Samantha N. Schlemmer From the Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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Alycia P. Fratzke From the Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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Richard J. Ploeg From the Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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Canaan Whitfield-Cargile Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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Carolyn Arnold Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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Aline Rodrigues-Hoffmann From the Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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Caitlin E. Older From the Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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Unity Jeffery From the Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77845.

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 VetMB, PhD

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History

A 16-year-old 487.2-kg (1,071.8-lb) Quarter Horse gelding was presented to a veterinary medical teaching hospital because of a 4- to 5-month history of intermittent, unilateral (right-sided) nasal discharge and epistaxis that did not improve with antimicrobial treatment. Additionally, right facial crest swelling had been observed approximately 3 weeks prior to presentation. The referring veterinarian performed skull radiography, which revealed a large mass lesion in the horse's right nasal cavity.

Clinical and Gross Findings

On physical examination, there was mildly decreased airflow from the right nostril, mildly increased expiratory noise on tracheal auscultation, and a small firm nodule over the right facial crest. Rhinoscopy revealed a well-circumscribed soft tissue mass in the right nasal cavity extending into the nasopharynx (Figure 1). Computed tomography of the head confirmed an expansile, soft tissue–attenuating mass that extended rostrally from the right ethmoid turbinates and filled large portions of the right conchonasal sinus, right nasal meatus, and choanal region. There was expansion, thinning, and multifocal lysis of a few adjacent ethmoid and nasal turbinates in addition to lysis and periosteal proliferation of the right maxillary bone along the facial crest. A frontonasal sinusotomy was performed under standing sedation and local anesthesia. The mass occupied most of the right paranasal sinus space and was removed by means of a combination of sharp and blunt dissection. The excised mass was friable, tan to red, and multilobulated and measured 9.6 × 5.7 × 5.5 cm. Impression smear slides were prepared, and the remaining tissue was submitted for histologic evaluation.

Figure 1
Figure 1

Endoscopic image (obtained by rhinoscopy) of a right-sided sinonasal mass in a 16-year-old Quarter Horse gelding that had a 4- to 5-month history of intermittent, unilateral nasal discharge and epistaxis. Rhinoscopy and CT had revealed a soft tissue mass extending rostrally from the nasal turbinates and filling large portions of the right conchonasal sinus, right nasal meatus, and choanal region. The mass was friable, tan to red, and multilobulated on excision. Bars are concealing patient information.

Citation: Journal of the American Veterinary Medical Association 258, 4; 10.2460/javma.258.4.379

Cytologic and Histopathologic Findings

Microscopic examination of impression smear slides revealed marked neutrophilic, macrophagic, and plasmacytic inflammation, with frequent Langhans multinucleated giant cells and abundant intracellular and extracellular yeast-like organisms and hyphal structures (Figure 2). The yeast-like organisms were round to ovoid and measured approximately 10 to 50 μm in diameter. They had a thin, approximately 2- to 3-μm-thick, clear cell wall and a medium blue body that often had a granular appearance. The hyphal structures were approximately 10 to 15 μm in width, were septated, and had parallel to irregular, dilated cell walls; branching was not observed. Histologically, the excised mass had evidence of similar pyogranulomatous inflammation and yeast-like organisms, which rarely had a pigmented cell wall following routine H&E staining (Figure 3). Gomori methenamine silver and Fontana-Masson staining of sections of the mass were performed, and the yeast-like structures were highlighted with stain uptake; these findings supported fungal organisms with melanin in the cell walls, respectively.

Figure 2
Figure 2

Photomicrographs of an impression smear of the excised sinonasal mass. There is marked neutrophilic, macrophagic, and plasmacytic inflammation with abundant intracellular and extracellular yeast-like organisms. The yeast-like organisms are round to ovoid, measure approximately 10 to 50 μm in diameter, and have a thin, approximately 2-μm-thick, clear cell wall and a medium blue body that is often of granular appearance. Modified Wright stain; bar = 20 μm. Inset—Rare hyphal structures that are approximately 10 to 15 μm in width with septations and parallel to irregular, dilated cell walls (arrow) are present. Modified Wright stain; bar = 20 μm.

Citation: Journal of the American Veterinary Medical Association 258, 4; 10.2460/javma.258.4.379

Figure 3
Figure 3

Photomicrographs of sections of the excised sinonasal mass. Expanding the submucosa are large numbers of macrophages, Langhans multinucleated giant cells, neutrophils, plasma cells, and few lymphocytes. Within the cytoplasm of multinucleated giant cells (arrows) and free within the tissue (arrowheads), there are numerous yeast-like organisms. These organisms are 10 to 20 μm in diameter and have a 2- to 3-μm-thick clear cell wall and vacuolated, eosinophilic to basophilic cytoplasm. H&E stain; bar = 100 μm. Inset—The cell walls of the yeast-like organisms stain dark brown with Gomori methenamine silver stain, indicating their fungal origin. Gomori methenamine silver stain; bar = 50 μm.

Citation: Journal of the American Veterinary Medical Association 258, 4; 10.2460/javma.258.4.379

Additional Laboratory Testing

Panfungal PCR amplification targeting the internal transcribed spacer 2 region of the fungal genome was performed on scrapings of the impression smears and scrolls of the formalin-fixed paraffin-embedded tissue, as previously described.1,a A 350–base pair band was amplified, excised, and submitted for sequencing. Alignment of 255 base pairs of the resulting sequence with the National Center for Biotechnology Information's nucleotide Basic Local Alignment Search Tool yielded matches to Curvularia spp.

Morphologic Diagnosis and Case Summary

Morphologic diagnosis: marked, chronic, diffuse, pyogranulomatous rhinitis with intralesional pigmented fungi consistent with Curvularia spp.

Case summary: unilateral (right-sided) sinonasal fungal granuloma as a result of phaeohyphomycosis (Curvularia infection) in a Quarter Horse.

Comments

On the basis of clinical signs and advanced imaging findings, ethmoid hematoma was the primary differential diagnosis for the mass in the horse of the present report. However, other differential diagnoses included a granuloma (secondary to a foreign body or infectious agent) or neoplasm (ranging from a benign polyp to aggressive carcinoma).2 In this case, microscopic examination of impression smears of the mass yielded a diagnosis of infectious (specifically fungal) disease before results of histopathologic evaluation were available, which allowed for a prompt adjustment of the horse's treatment protocol. The morphological characteristics of the infectious agent, namely polymorphic yeast-like structures with rare (in cytologic preparations) or absent (in tissue sections) hyphal structures, were considered unusual by both the veterinary clinical and anatomic pathologists. These structures were rarely pigmented. These findings taken together with the results of tissue section staining with Gomori methenamine silver and Fontana-Masson stains led to a morphologic diagnosis of phaeohyphomycosis, which was later confirmed by results of a panfungal PCR assay and sequencing.

Phaeohyphomycosis is an emerging opportunistic fungal infection that typically results in cutaneous or subcutaneous nodular lesions, but systemic and neurologic forms are also reported.3,4 These fungi are pigmented (dematiaceous), are saprophytic, and inhabit soil, plants, and wood. As such, they are considered ubiquitous, but infections appear more prevalent in warm, tropical to subtropical climates. Infection is thought to occur via traumatic implantation or wound contamination; immunosuppression of the host may also be a contributing factor.3,4 In equids, the most frequently reported agents that cause phaeohyphomycosis are Alternaria spp, Drechslera spicifera, and Curvularia spp.5,6,7,8,9,10,11,12 In conjunction with PCR assay results, findings of histologic examination and fungal culture of excised tissue or tissue aspirates are often used to provide a definitive diagnosis. Sabouraud dextrose agar and potato dextrose agar are the recommended culture media on which to isolate these agents.3,4 General treatment recommendations for phaeohyphomycosis involve surgical excision (if amenable) and treatment with antifungal agents (local or systemic administration, or both).3,4

Curvularia spp have been implicated in phaeohyphomycotic infections in horses, dogs, cats, and humans.13,14,15 The macroconidia of Curvularia lunata have 3 septae and 4 cells, whereby the second cell from the conidiophore tip has a thicker wall that swells and causes a characteristic bend or curve.16 There are reports10,14,17 of Curvularia spp, Alternaria spp, and Drechslera spp that have bulbous terminal dilations of the hyphal elements, which are described as chlamydospore-like or chlamydoconidium-like. This characteristic may have accounted for the unusual yeast-like forms that predominated in specimens obtained from the horse of the present report. Treatment of Curvularia infections is the same as treatment of other phaeohyphomycoses. Antifungal susceptibility profiles derived from samples collected from humans with nasal Curvularia infections indicate that echinocandins, amphotericin B, and posaconazole are more effective agents than voriconazole and itraconazole.15

Primary localized intranasal phaeohyphomycosis in horses has not been reported to the authors' knowledge. Potential mechanisms of infection could include traumatic inoculation or inhalation of contaminated foreign or plant material, along with concurrent compromise to the nasal mucosa or mucosal immunity that could occur with local or systemic immunosuppression. Curvularia spp have been isolated from the conjunctiva of healthy Thoroughbred mares in Florida18 and could be part of the nasal mucosal microbiome; if so, alterations to the mucosa could predispose horses to opportunistic infection. Additionally, Curvularia spp have been identified as contaminants in feed for racehorses in Argentina,19 which may allow for increased potential for developing opportunistic infection.

The horse of the present report was hospitalized for 1 week following excisional biopsy of the mass. While in the hospital, the horse received a tetanus toxoid booster vaccine, antimicrobials (penicillin and gentamicin), an anti-inflammatory drug (flunixin meglumine), and antifungal agents (local administration of amphotericin B via transendoscopic rhinoscopic injection into the area of previous mass removal [right sinonasal region] and oral administration of fluconazole). Nasal airflow normalized following the excisional biopsy. The horse was discharged from the hospital, and the owner was instructed to continue treatment with fluconazole and taper the dosage of flunixin meglumine. Three weeks after surgery, the horse had mild, right-sided, serous nasal discharge and a smaller, firmer facial crest swelling. Repeated rhinoscopy revealed no evidence of fungal granuloma regrowth. Fluconazole treatment was continued for a total of 6 weeks. At the 6-month recheck, there was no rhinoscopic evidence of recurrence of a fungal granuloma.

Acknowledgments

Funding sources did not have any involvement in the study design, data analysis and interpretation, or writing and publication of the manuscript. The authors declare that there were no conflicts of interest.

This case was presented at the 2018 Annual American College of Veterinary Pathologists and American Society for Veterinary Clinical Pathology Conference, Washington, DC.

The authors thank Alexandra Hughey for technical assistance.

Footnotes

a.

Myers AN, Older CE, Thomas JE, et al. Panfungal PCR for identification of fungi in skin cytologic preparations (abstr), in Proceedings. 31st N Am Vet Derm Forum 2018;106.

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