A clinico-pathological and cytological study of oral candidiasis

Candidiasis of the oral mucosa arises chiefly as a result of infection with Candida albicans. Many clinicopathological analyses of macroscopic findings have been described, although the clinical findings of oral candidiasis vary considerably and the conditions are complex. The present study analyzes the distribution, clinical, cytological and histological diagnoses of oral candidiasis, associated complex diseases and the diagnostic value of cytology. The ratio of Candida infection was 28.9% among 1551 study participants. Females were infected significantly more often than men (p < 0.01) and the affected age range was 60 79 years (61.0%, p < 0.01). The predominantly affected areas were the tongue (48.3%, p < 0.01) and gingiva (20.0%, p < 0.01), and occurrence at multiple loci was seen in 43 (9.6%) patients. The typical clinical findings of oral candidiasis were ulcerative/erythematous lesions (33.2%, p < 0.01) and pseudomembranous candidiasis (31.6%, p < 0.01). A histopathological diagnosis of candidiasis based on biopsy specimens from 26 lesions in patients with Candida infection indicated by cytology was confirmed from cultures. The breakdown of a cytological to a definite diagnosis was 6 positive (SCC 4, verrucous carcinoma 1, moderate to severe dysplasia 1), 6 suspected positive (mild dysplasia, 2; moderate to severe dysplasia, 2; papilloma, 1 and SCC, 1) and 14 negative (epulis, 3; papilloma, 3; granulation tissue, 2; fibrosis, 2 and others, 4). Exfoliative cytology can easily judge the presence of Candida species, although experience is necessary for the presumptive diagnosis of an oral mucosal disease. The application of exfoliative cytology using the Periodic acid-Schiff reaction is helpful for the earlier detection of oral candidiasis with various macroscopic findings.


INTRODUCTION
Candidiasis in the oral mucosa is usually caused by Candida albicans, which is an indigenous fungus in the oral cavity of healthy individuals.However, oral candidiasis can develop as a result of decreased host immunity, that is, as an opportunistic infection.The causes of oral candidiasis include being elderly or being an infant, having AIDS or diabetes, various drugs and local factors such as wearing dentures, steroid preparations and xerostomia.Many macroscopic findings of clinico-pathological analyses have been reported, although oral candidiasis has a variable clinical presentation and thus can be difficult to precisely diagnose.Exfoliative cytology to screen for oral mucosal disease has been performed for 30 years at our hospital and all specimens are checked for Candida.Additionally, the accuracy of detecting Candida by exfoliative cytology has already been proven by simultaneous culture testing [1].
The present study analyzes the distribution of oral candidiasis screened by exfoliative cytology according to sex, location, age and clinical findings.Clinical, cytological, histological diagnoses and complicated diseases associated with oral candidiasis and the effectiveness of cytology as a diagnostic tool are examined and discussed.

MATERIALS AND METHODS
We initially enrolled 1551 patients who presented mainly due to oral mucosal abnormalities, and who were diagnosed with a Candida infection by exfoliative cytology between April 2008 and March 2009 at the Department of Diagnostic Pathology at the Hospital of Nihon University School of Dentistry at Matsudo.All cytologi-cal specimens were examined by Papanicolaou (Pap) staining and the Periodic acid-Schiff (PAS) reaction, and reconfirmed by an internationally qualified cytological screener and three specialists in oral cytopathology.Candida infection was diagnosed when spores, pseudohyphae and/or mycelia were confirmed by PAS reaction.Candida infection in those with only detectable spores was confirmed by colony formation and culture (Nissui Pharmaceutical Co. Ltd., Tokyo, Japan).Six cases performed biopsy immediately among 12 cases in which the malignant tumor was suspected, cytological and clinically.The 6 remaining cases transferred to another hospital at the patient's requests.The 437 cases except these 12 cases were performed intraoral re-examination after they had removed Candida.Biopsies were obtained from those with consistent macroscopic findings and diseases were histopathologically diagnosed by three oral pathologists using hematoxylin and eosin staining (H.E.) to determine more complex diseases.Histopathological diagnoses followed the diagnostic criteria of the World Health Organization WHO [2].Data were analyzed according to the age, location, clinical diagnosis, cytological diagnosis, histopathological diagnosis and disease complexity.The Ethics committee of Hospital of Nihon University School of Dentistry at Matsudo approved this study, and all patients provided written, informed consent to participate in all procedures associated with the study.All data were statistically analyzed using the Chisquare test (SPSS).

Cytological and Histopathological Diagnoses
Cytology with the PAS reaction detected Candida infection with 100% precision.That is, Candida infection was confirmed by mycelia growth in all of the cultures that tested positive by PAS.

Treatment for Candida Infection
The 437 patients in whom Candida infection was cytologically diagnosed were treated with an antifungal drug.These strategies resulted in the disappearance of the fungal mycelia from 432 cases (98.9%).

DISCUSSION
Oral candidiasis is a common opportunistic infection in individuals with decreased immunity.Physiological factors that predispose individuals to oral candidiasis comprise pregnancy, immune defects, drugs and malnutrition, and local factors including trauma, denture-associated problems and oral cancer [3].Most reports have relied on macroscopic observation by dental clinicians, although many reports have described clinico-pathological studies of oral candidiasis.The present epidemiological study examined oral candidiasis detected by exfoliative cytology and by visible cultures.We also identified the value of oral exfoliative cytology for diagnosing oral candidiasis.

Ratio of Candidiasis
Candida species comprise the most common opportunistic fungal pathogens in humans, with C. albicans being the most prevalent cause of mucosal and systemic infection.C. albicans has been described as the most frequently encountered oral fungal commensal with detection rates of 40% to 65% in healthy adults [4].The ratio of oral candidiasis in the present study was 28.9%, which was similar to the reported 24% of outpatients at a dental clinic [5] and 24.5% in a review of eight publications [6].
On the other hand, the rate of candidiasis was 14.09% in a large-scale Brazilian study of 1586 randomly selected individuals [7].However, the detection rates were very low when Candida infection was determined only from interviews and macroscopic observations.

Epidemiological Features
Infection rates were influenced by age and removable prostheses in a Brazilian study [7].Age-matched statistical analysis in the present study found a significantly higher infection rate among 60 -79-year-olds than in any other age group.Many factors have been investigated, such as an impaired host defense causing deceased Salivary flow [8], an increase in the morbidity rate of diabetes [9], wearing dentures [10], and taking medicine to treat chronic [11] and auto-immune diseases such as Sjögren syndrome [8].The prevalence rate of oral candidiasis among children with oral mucosal diseases was the highest among those aged 0 -12 years (28.4%)[12], which was similar to findings from other countries [13][14][15].The ratio of 0 -19-year-olds was very small in the present study.Rare symptoms of oral candidiasis in children might have been one of the causes.The higher prevalence of candidiasis among women in the present study is in agreement with the findings of other studies [16,17].In fact, 62.9% of the patients who presented with the chief concern of oral mucosal abnormalities were female in the present study Furthermore, xerostomia and autoimmune diseases that cause oral candidiasis are prevalent among women.Half of our patients with a Candida infection had lesions that were concentrated mostly on the dorsum and edges of the tongue.The dorsal sur-face is the main ecological niche for Candida in the oral cavity [4,8,11,18].Presumably, chronic contact with dentures [10] and relationships with oral mucosal diseases such as leukoplakia and injuries might explain the high frequency of infections being located on their edges.Moreover, since multiple symptoms were quite abundant (15.6%), we considered that factors such as age, drugs and immune defects were involved.

Clinical Manifestations
The clinical classification of candidiasis is highly complex because the findings are diverse.Therefore, we categorized candidiasis into acute, chronic and Candida-associated lesions based on Lakshman's classification [3].We concentrated on the ulcerative/erythematous and pseudomembranous types.An inflammatory reaction was obvious in ulcerative/erythematous and Candidaassociated lesions.The hyphae of C. albicans tightly adhere to epithelial cells, and proteinases secreted by the hyphae damage the oral mucosa [19].Schaller et al. assert that C. albicans proteinase causes tissue damage and increasing vascular permeability leads to an inflammatory reaction and clinical symptoms [20].Chronic erythematous candidiasis is associated with corticosteroids, antibiotics and HIV infection.Dentists often treat stomatitis with triamcinolone acetonide, which is routinely available at Japanese drugstores and prolonged use of this drug can become problematic [21].In addition, candidiasis can be a side effect of the inhaled steroids that are used to treat asthma [22] and allergosis.Because erythematous candidiasis is similar to a non-specific inflammatory reaction, it should be cytologically diagnosed as soon as possible.The reported ratio of denturerelated stomatitis (DRS) ranges from 11% to 67% [23].
A removable prosthesis is the most common cause of the growth and pathogenicity of Candida species [4,18,24].Angular cheilitis is also associated with yeasts and bacteria in relation to wearing dentures [3].Candida species proliferate by contact with the resin [10], and Candida counts significantly correlate with the intensity of denture plaque scores [25].The rate of hyperplastic candidiasis that macroscopically presented like leukoplakia was 12.2% in the present study, and the malignant transformation rate was high [26].Simultaneous Candida infection and several etiological factors seemed to play a role in malignant transformation [27].Candida species were identified in 43.7% of the patients with lichen planus and leukoplakia in their oral cavities [28].The reported prevalence of oral candidiasis varies between 8% and 94% in patients with advanced cancer, because of differences in diagnostic criteria, diagnostic methods and the study population [29].Whether a condition depends only on a Candida infection or such infection with coexistent mucous membrane diseases should be determined as soon as possible.Macroscopic classification is limited as most epidemiological surveillance concerning oral candidiasis considers the candidiasis, DRS and cheilitis as separate entities [17,30].

Accuracy of Exfoliative Cytology
Information about investigating Candida infection of the cervical area using Pap smears is very scarce [31].Candida species have been detected based on the growth of hyphae on PAS smears [4,6].The high accuracy of detecting oral candidiasis by exfoliative cytology was demonstrated here, as well as by others [1].The cytological detection of candidiasis is simple, inexpensive, accurate and painless.As for oral candidiasis, it is clinically variegated to present the findings of leukoplakia or intractable ulcerative lesion, etc.In this result, the abbreviation half of oral candidiasis was occupied by these confusing clinical view.Therefore, discovery of candidiasis by cytology was useful for avoiding unnecessary biopsy.In addition, as a result of giving antifungal drug immediately, as for candidiasis detected by cytological diagnosis, the fungal mycelia disappeared with 98.9% of these cases.However, Candida can be over-and underdiagnosed when other mucosal diseases coexist, especially dysplasia and SCC.The size and shape of oral epithetlial cells infected with Candida significantly change [1,32].Judgment of changes between atypia by Candida and dysplastic change should be required experience.In that case, judgment becomes possible by carrying out observation of a macro-scopic view, and exfoliative cytology after antifungal drug.In Japan, there is a custom which applies triamcinolone acetonide easily to stomatatis.Moreover, since triamcinolone acetonide is marketing, using it for a long period of time may be continued by a patient's judgment, and it tends to merge the side effects of the Candidal infection [33].Cell atypia was observed in epithelial cells of the decubitus ulcer accompanied by the Candidal infection which uses triamcinolone acetonide for a long period of time, in this study.The observation of cytological specimen of intractable ulcer after the long-term application of triamcinolone acetonide should be carefully.The presence or absence of Candida species can be easily determined by exfoliative cytology, although experience is necessary for a presumptive diagnosis of oral mucosal disease.Exfoliative cytology using the PAS reaction enables earlier detection of oral candidiasis that presents with macroscopically variable symptoms.

Table 1 .
Distribution of the patients of oral candidiasis.
**: A significant difference (p < 0.01) was observed among all the age groups by chi-square test.

Table 2 .
The location of oral candidiasis.

Table 3 .
Clinical diagnoses of oral candidiasis.
**: A significant difference (p < 0.01) was observed among all the age groups by chi-square test.

Table 4 .
Result of cytology, treatment and biopsy.