Respiratory System

Nose - Fungus

Narrative
Comment:
Fungal organisms are occasionally seen in the nasal cavities of mice and rats from NTP toxicity/carcinogenicity studies, more commonly in rats. Mats of fungal mycelia may occur within the nasal passages (Figure 1, Figure 2, Figure 3, and Figure 4), but tissue invasion is extremely rare.

Based on fungal morphology (characteristic fruiting heads and hyphal branching patterns) and reports in the literature, the fungal organisms are usually an Aspergillus sp., with Aspergillus fumigatus being the most common. Aspergillus spp. have characteristic fruiting heads and hyphal branching patterns (Figure 3). The fungi are typically accompanied by suppurative inflammation. Changes such as hyperplasia and metaplasia are usually present in the adjacent epithelium, and there is often acute to chronic-active inflammation in the associated underlying lamina propria.
Recommendations:
Fungus should be diagnosed whenever present but should not be graded. The morphologic features of the fungal organisms should be described in the narrative. The fungal genera/species cannot be definitively identified by histopathology alone; however, it may be stated that the morphologic features are consistent with a particular type of fungal organism. When warranted by severity, all associated lesions should be diagnosed separately and assigned severity grades. Whenever possible, it should be noted in the narrative whether or not the associated lesions are secondary to the presence of the fungus or if they may be related to treatment.
References:

Boorman GA, Morgan KT, Uraih LC. 1990. Nose, larynx, and trachea. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, eds). Academic Press, San Diego, 315-337.

Everitt JI, Richter CB. 1990. Infectious diseases of the upper respiratory tract: Implications for toxicology studies. Environ Health Perspect 85:239-247.

Full Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1568352/

Herbert RA, Leninger JR. 1999. Nose, larynx, and trachea. In: Pathology of the Mouse: Reference and Atlas (Maronpot RR, ed). Cache River Press, Vienna, IL, 259-292.

National Toxicology Program. 1986. NTP TR-300. Toxicology and Carcinogenesis Studies of 3-Chloro-2-methylpropene (Technical Grade Containing 5% Dimethylvinyl Chloride) (CAS No. 563-47-3) in F344/N Rats and B6C3F1 Mice (Gavage Studies). NTP, Research Triangle Park, NC.

Abstract: https://ntp.niehs.nih.gov/go/6603

Nyska A, Kuttin ES. 1988. Upper respiratory tract infection in mouse and rats. Mycopathologia 101:95-98.

Abstract: https://www.ncbi.nlm.nih.gov/pubmed/2963960
  • Image of fungus in the nose from a male F344/N rat in a chronic study

    Nose - Fungus in a male F344/N rat from a chronic study. A mat of fungal hyphae is present in the lumen of the nasal cavity and is accompanied by epithelial changes and inflammation of the nasal tissue.

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<p>Nose - Fungus in a male F344/N rat from a chronic study. A mat of fungal hyphae is present in the lumen of the nasal cavity and is accompanied by epithelial changes and inflammation of the nasal tissue.</p>

Nose - Fungus in a male F344/N rat from a chronic study. A mat of fungal hyphae is present in the lumen of the nasal cavity and is accompanied by epithelial changes and inflammation of the nasal tissue.
<p>Nose - Fungus in a male F344/N rat from a chronic study (higher magnification of Figure 1). The hyphae are visible in the fungal mat.</p>

Nose - Fungus in a male F344/N rat from a chronic study (higher magnification of Figure 1). The hyphae are visible in the fungal mat.
<p>Nose - Fungus in a male F344/N rat from a chronic study. Characteristic pigmented fruiting heads and hyphae are shown in a fungal mat from the nasal cavity.</p>

Nose - Fungus in a male F344/N rat from a chronic study. Characteristic pigmented fruiting heads and hyphae are shown in a fungal mat from the nasal cavity.
Nose - Fungus in a male F344/N rat from a chronic study. Silver staining techniques, such as this Gomori's methenamine silver stain, highlight the fungal organisms.
Nose - Fungus in a male F344/N rat from a chronic study. Silver staining techniques, such as this Gomori's methenamine silver stain, highlight the fungal organisms.

Authors

Rodney A. Miller, DVM, PhD, DACVP
NC Pathology Group Manager
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Mark F. Cesta, DVM, PhD, DACVP
Staff Scientist, NTP Pathologist
Cellular and Molecular Pathology Branch
Division of the National Toxicology Program
National Institute of Environmental Health Sciences
Research Triangle Park, NC

Reviewers

Robert R. Maronpot, DVM, MS, MPH, DACVP, DABT, FIATP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Ronald Herbert, DVM, PhD
NTP Pathologist
Group Leader, Pathology Support Group
Division of the National Toxicology Program
National Institute of Environmental Health Sciences
Research Triangle Park, NC