Fordyce's Granules of the Incisor and Molar Gingiva in F344 Rats

Abstract

Abstract. Fordyce's granules were observed in the gingiva of the upper incisor and molar teeth in F344 rats. The data were based on 734 males and 722 females that were used as control and treated animals in 26-week, 65-week, and 2-year studies by the National Toxicology Program. The incidence of Fordyce's granules was markedly different when comparing sex, age, and site of the lesion. Fordyce's granules were very common in the midsagittal gingiva of the upper incisor in males and increased in incidence with age (34.2, 50, and 56.3% in 26-week, 65-week, and 2-year studies, respectively). The granules of the incisor gingiva were rare in females (0, 0, and 2.8% in 26-week, 65-week, and 2-year studies, respectively). Fordyce's granules of the molar gingiva were very rare in both sexes and were found only in 9/734 (1.29'0) males and in 3/722 (0.4%) females. Only three unilateral granules of the molar were grossly recognized as focal swelling of the gingiva or a white nodule with a huge cyst in the third upper molar. Histologically, Fordyce's granules were arranged as a collection of sebaceous glands unassociated with hair follicles. In addition, the granules of the molar gingiva were associated with cystically dilated ducts filled with sebum. Ultrastructurally, the sebaceous cells were characterized by varying numbers of cytoplasmic lipid droplets and occasional desmosome and hemidesmosome formation. Fordyce's granules previously reported in rats of other strains were also reviewed and compared with those in F344 rats in regard to incidence, location, and age.

Spontaneous Ectopic Sebaceous Glands (Fordyce's Granules) in the Oral Mucosa of Sprague-Dawley Rats

“…These results were essentially consistent with the data from previous investigators, suggesting that Fordyce's granules are more extensively seen in the anterior portion of the molars of aged males [9][10][11][12] . In Holtzman, Long-Evans, and Wistar strain rats, the locations of Fordyce's granules have been reported to be only in the anterior gingiva of the first upper or lower molar [9][10][11] .…”

“…In humans, Fordyce's granules had the secreting function with true ducts, which were usually plugged with keratin 6 . In F344 strain rats, the duct was reported to be occluded by sebum plugs, followed by the formation of cystic dilatation 12 . Based on these data, cystic dilatation in the duct may be brought about by the presence of plugs derived from the sebum and/or food intake, leading to the cyst formation in the excretory ducts.…”

“…Additionally, the granules are recognized to occur frequently and bilaterally in the buccal, labial, retromolar mucosa, and vermilion border of the lip 2,[4][5][6] . In other species, Fordyce's granules have been reported as ectopic sebaceous glands in the soft palate of the guinea pig 7 , the lip of the chimpanzee 8 , and the gingiva of rats [9][10][11][12] . In rats, ectopic oral sebaceous glands have previously been reported in Holtzman, Long-Evans, Wistar, and F344 strains, and their morphological features closely resemble human Fordyce's granules used as a common name.…”

Nonproliferative and Proliferative Lesions ofthe Gastrointestinal Tract, Pancreas andSalivary Glands of the Rat and Mouse

“…Pathogenesis: This developmental change consists of aggregates of ectopic dermal sebaceous glands (Fordyce’s granules) in the oral cavity of rats ( Yoshitomi et al 1990 ) and is associated with gingival mucosa. This is most common in the F344 strain and seen primarily in males.…”

Wistar and Sprague–Dawley rats

“…In rats, there are, at present, only four reports of intraoral 'ectopic' sebaceous glands in the literature (Bernick & Bavetta 1962, Frandsen 1962, Rulli & Martinelli 1971, Yoshitomi et al 1990. In Holtzman and Long-Evans rats, as well as in Wistar rats, Fordyce's granules are found in the molar gingiva.…”