Among malignant tumors in Korean women, cervical cancers have been reported as the fifth most common form of cancer after breast, stomach, colorectal, and thyroid cancers [1]. Recently, however, the occurrence of cervical cancer has decreased as it takes considerable amount of time to develop invasive cancers through a progress of dysplasia and intraepithelial carcinoma, and early detection of precancerous lesions is readily available due to periodic screening and the development of cervical cancer examination methods utilizing colpos copy and human papillomavirus (HPV) tests [2].

Pap smears are the most frequently utilized method for cervical cancer screening. The Pap smear technique was first developed by Papanicolaou and Taut [3], in 1941, and although it is a convenient, inexpensive, and safe method for cervical cancer screening, the rate of false negative errors is between 6% and 55%. In order to improve upon this error rate, liquid-based Pap [4], colposcopy, and human papillomavirus tests have been suggested as alternative screening methods [5]. Likewise, 'The Bethesda System' (TBS) was established by the National Cancer Institute meeting, held in Bethesda, USA in 1988, to address problems regarding diagnostic classification of Pap smear results. Currently, a variety of classification methods are utilized around the world, especially in the US. Specifically, atypical squamous cells of undetermined significance (ASCUS) and atypical glandular cells of undetermined significance (AGUS) are among the most important characteristics of TBS. According to TBS, ASCUS is defined as foremost by abnormal cells observed are worse than either reparative or reactive cells, and secondly as cells that do not satisfy the quantitative and qualitative criteria of squamous intraepithelial lesions [6], where AGUS are defined as those cells that satisfy the range of positive reactive changes but are not enough sufficient to be diagnosed as invasive adenocarcinomas [7]. In 2001, the Bethesda III classification, the terminology of both ASCUS and AGUS, were updated as ASC and atypical glandular cell (AGC), respectively; where ASC is subdivided into ASC-US and ASC-H while AGUS is subdivided into AGC-not otherwise specified (NOS) and AGC-favor neoplastic, respectively, and are now utilized in clinical diagnoses [8].

ASCUS findings accounts for 3% to 5% of Pap smear results, although this figure has been reported to vary between 10% to 20% and 3% to 5% of the diagnosed patients possessed the risk of cervical intraepithelial neoplasia (CIN)1 and CIN2 or CIN3, respectively. A significant proportion of ASCUS patients with CIN1 are accompanied by positive HPV infection, the lesions of which have been reported to spontaneously disappear in more than 60% of cases. Thus, follow-up analysis via an outpatient clinic after confirming whether lesions of grade CIN2 or CIN3 are present in the patients who were diagnosed ASCUS appears to be an important research avenue [9-13]. Indeed, the prevalence of AGC accounts for 0.08% to 5.96% of known cases, and it has been shown that 8% of diagnosed patients are associated with malignant lesions, thereby requiring more attention and additional histological examinations and outpatient clinic follow-up for the patients clinically diagnosed with AGC [14].

Thus, the objective of this study was to investigate the clinical significance of AGC (AGC-NOS, AGC-favor neoplastic) by analyzing the final diagnosis results obtained from biopsies of female patients diagnosed with AGC based on the TBS classification method according to Pap smear.

Pap smears are a meaningful diagnostic tool for identifying early stages of precancerous lesions of cervical cancers, thereby reducing cancer mortality. Thus, when examination results indicate the presence of cell abnormalities accurate interpretation and subsequent follow-up is critical. In the present study, we aimed to analyze the meaning of Pap smear results in females who diagnosed as AGC (NOS, favor-neoplastic) among the females who had abnormal Pap smear results during regular check-ups. A total of 83 of 54,160 subjects (0.15%) were diagnosed with AGC, which was in agreement with a previously reported value of 0.08% to 5.96% [14], indicating that AGC diagnosis our hospital can be considered relatively well managed.

A total of 64/51,510 subjects (0.12%) and 19/2,650 subjects (4.9%) were diagnosed via conventional Pap and liquid-based Pap (ThinPrep), respectively. AGC-NOS was present in 41/51,510 subjects (0.08%) for conventional Pap and 14/2,650 subjects (0.53%) for liquid-based Pap. In addition, AGC-favor neoplastic were observed in 23/51,510 subjects (0.04%) for conventional Pap and 5/2,650 subjects (0.19%) for liquid-based Pap. Given these results, diagnosis of AGC (NOS, favor-neoplastic) was relatively more frequent in liquid-based Pap than that of conventional Pap (P=0.011), and thus AGC diagnosis utilizing liquid-based Pap appeared to increase the frequency of diagnosis. However, as liquid-based Pap accounted for only 2,650/54,160 subjects (4.9%), it is somewhat unreasonable to determine an overall diagnosis ratio, and more results are needed to support whether this observation is clinically relevant.

Since it has been reported that HPV18 is highly associated with cervical adenocarcinoma [15], we investigated the correlation of HPV infection. In AGC, HPV infection was present in 10/26 subjects (38.4%) including 1 case of low risk infection and 9 cases of high risk of infection. In cases of high risk HPV infection, 5/10 subjects (50%) and 4/16 subjects (25%) exhibited AGC-favor neoplastic and AGC-NOS, respectively, indicating that the high risk infection was significantly higher in AGC-favor neoplastic compared with AGC-NOS. Of the cases of HPV observed, type 18 accounted for 1 case, while type 33 accounted for 3 cases; these represent the most common types of HPV infections. Even though these results represent different patterns within cervical adenocarcinoma, evaluation of more subjects is required to determine whether there is a direct correlation, due to the small number of patients in this study.

The average CA-125 of patients with AGC was 50.8 ±101.6 (U/mL), whereas the average CA-125 in AGC-NOS and AGC-favor neoplastic was 24.4 ± 36.5 (U/mL) and 97.6 ±155.4 (U/mL), respectively. Although the average CA-125 was higher in AGC-favor neoplastic, it was difficult to establish whether these values were significant due to the large standard deviation.

Chhieng et al. [16], reported that AGUS (AGC) is highly correlated to malignant diseases (15.45%). Moreover, Seok et al. [17], reported that invasive diseases were found in 50 subjects (57.4%) during histologic examination, among 87 subjects who were diagnosed with AGUS by Pap smear. In the present study, 24/83 subjects (28.9%) were diagnosed with malignancy in the histologic examination results of the patients with AGC, indicating high correlation. Particularly, the frequency of AGC-favor neoplastic (16/28 subjects, 57.1%) was significantly higher than that of AGC-NOS (8/55 subjects, 14.6%), indicating that AGC-favor neoplastic was relatively more correlated to malignant diseases (P=0.000). In patients with AGC, cervical adenocarcinoma (8/83 subjects, 9.6%) was the most frequently observed malignant disease, followed by, in decreasing order, endometrial cancer (6/83 subjects, 7.2%), ovarian cancer (4/83 subjects, 4.8%), breast cancer (3/83 subjects, 3.6%), and stomach cancer (3/83 subjects, 3.6%). Recently, Schnatz et al. [18,19], and Sharpless et al. [20], also found that malignancy in extrauterine organs, primarily the large intestine and breast, can be observed in histologic examination results of patients with AGUS.

Based upon the results above, liquid-based Pap smear, colposcopy and biopsy, human papillomavirus tests, and cervical curettage are needed in patients with AGC to obtain appropriate examination results; cervical curettage may be especially important for patients who aged 35 years and older, or who possess risk factors for endometrial cancer. Moreover, examination of abnormalities within the pelvis, including pelvic examination and pelvic sonography, is also necessary.

If no abnormalities are observed according the examinations described above, additional evaluation of extrauterine adenocarcinoma such as breast examination, gastroscopy, and colonoscopy is recommended, with consideration of the patient's age. Regardless of such comprehensive examinations, a 4.7% false negative error rate has been reported [18]. Thus, it is suggested that follow-up be carried out with Pap smear every 4 to 6 months, even if patients appear to be normal according to the examinations listed above.

Given the results of the study, we can speculate that AGC, especially in cases of AGC-favor neoplastic, may be associated with adenocarcinoma (e.g., ovarian cancers, breast cancers, stomach cancers) or certain modifications found before or after AGC formation. Large-scale investigations with more subjects and investigation of the molecular basis for these results are warranted.