From January 1, 2012, to December 31, 2021, a total of 1358 AT patients were confirmed in our institution, including 534 in the first stage (2012–2016) and 824 in the second stage (2017–2021), with an increasing rate of 54.3%. The number of incidences demonstrated increasing trends according to the research results.
Patel et al. [6] retrospectively analyzed 3994 AT patients, with a median onset age of 54 years. Ebbehoj et al. [7] retrospectively investigated 1287 AT patients, with a median onset age of 62 years, of whom 49.7% were between 40 and 64 years and 42.2% were over 65 years. The mean onset and peak onset ages were 46.2 ± 12.4 years (14–80) and 41–50 years (28.4%), respectively. The above contents have indicated that the onset age of our center was lower than that of European and American countries.
AT most often occurs in females. Duralska et al. [8] retrospectively analyzed 881 AT patients, including 275 males and 606 females, with a gender ratio of 1:2.2. Battistella E et al.[9] retrospectively investigated 502 AT patients, including 212 males and 288 females, with a male to female ratio of 1:1.36. There were 1358 patients in our center, including 565 males (41.6%) and 793 females (58.4%), with a male to female ratio of 1.4:1. Between the two stages, there were more females than males. The gender ratio was consistent with previous reports in our center.
Different countries have racial differences even if the same country also has different ethnic groups. At present, there are few studies on whether national factors have affected the incidence rate of AT. Ebbehoj et al. [7] analyzed 1287 patients in the United States, including 1209 (93.9%) Caucasian, 34 (2.6%) African American, and 17 (1.3%) Asian patients. China is a multiethnic country with a total of 56 ethnic groups. Our medical center is located in Nanning, the capital of Guangxi Zhuang Autonomous Region. In addition to the Han ethnicity, there are also 11 ethnic minorities. The Zhuang ethnicity is the most common ethnic minority in China. There is currently no literature on the proportion of Han and Zhuang patients with AT. This study first found that there were 905 Han and 404 Zhuang individuals, with Han being higher than Zhuang (2.2:1). The majority of the two stages were Han, which is consistent with the ethnic composition in China.
AT tends to occur on the left side, while bilateral AT is rare in clinical practice as seen by its low incidence (7.6%) [10]. Azhar RA et al. [11] analyzed 160 ATs, which were 84 (52.5%) and 76 (47.5%) on the left and right sides, respectively. Conzo G et al. [12] analyzed 254 AT patients, with 124 (55.9%) and 108 (42.91%) on the left and right sides, respectively. Our study suggested that there were 714 (52.6%) and 625 (46.0%) cases on the left and right sides, respectively, with a tendency to occur on the left side, which is consistent with literature reports. However, there were only 19 (1.4%) cases of bilateral AT in our center, which is a lower incidence than that reported in the literature.
AT was divided into functional and nonfunctional types according to endocrine tests. Functional tumors secrete related hormones, causing corresponding clinical symptoms[13, 14]. When diagnosing AT, endocrine function tests must be performed to clarify the nature of the tumor. Our center confirmed 914 (67.3%) clinical types and 444 (32.7%) incidental types. In the second stage, 297 (36.0%) incidental types had increased proportions compared to 147 (27.5%) in the first stage. The clinical types decreased from 387 (72.5%) in the first stage to 527 (64.0%) in the second stage. There were 729 (53.7%) functional types and 629 (46.3%) nonfunctional types. The proportion of patients with nonfunctional types in the second stage increased from 50.4–40.1% in the first stage; the proportions of patients with functional types decreased from 59.9% in the first stage to 49.6% in the second stage. This may be related to the increasingly wide application of imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), in our center, resulting in increasing numbers of incidental and nonfunctional types.
Ebbehoj et al. [7] analyzed 1287 AT patients, with a median diameter of 1.5 cm (0.5–25.5 cm). Duralska et al. [8]explored 881 AT patients, with an average diameter of 4.2 cm (6–13 cm) and a median diameter of 4 cm. Zhao et al. [15]evaluated 621 AT patients with a median diameter of 1.74 cm (0.4–10.2 cm). The results of our study suggested that the median diameter was 2.6 cm (0.4–17.2 cm). There was no statistically significant in median diameter between the two stages, which was consistent with literature reports.
AT are mainly benign. Adenomas are the main pathological type of benign tumors. Ebbehoj et al. [7] investigated 1287 AT patients, including 1077 with adenomas and nodular hyperplasia (83.7%) and 14 with pheochromocytoma (1.1%). Duralska M et al. [8] analyzed 881 patients with adrenal tumors, including 391 adenomas (44.3%), 178 pheochromocytomas (20.2%) and 177 nodular hyperplasia (20.1%). A total of 1315 (96.8%) benign ATs were confirmed, including 508 (38.6%) nonfunctional adenomas, 298 (22.7%) PAs and 215 (16.3%) pheochromocytomas, which is consistent with previous literature reports.
The common pathological types of malignant tumors include ACC, adrenal metastatic tumors, lymphoma, etc[16–18]. Ebbehoj et al. [7] evaluated 1287 AT patients, including 111 (8.6%) with malignant tumors, 96 (7.5%) with adrenal metastatic tumors and 4 (0.3%) with ACC. Coste et al. [19] analyzed 520 AT patients and found 64 (12.3%) with malignant tumors, with 36 (6.9%) adrenal metastatic tumors being the most common pathological type, followed by 27 (5.2%) with ACC. However, the number of malignant patients in our center was only 43 (3.1%), with ACC being the most common malignant type, accounting for 17 (1.2%) patients, followed by 9 (0.6%) with adrenal metastatic tumors. Both the numbers of malignant tumors and the most common malignant pathological types differed from literature reports.
In 1992, Gagner et al. reported the world's first case of LA. Compared to open surgery, LA has advantages such as minimal damage, fast recovery, less pain, and shorter length of stay (LOS). For AT with a diameter less than 6 cm, laparoscopic techniques have replaced traditional open surgery as the gold standard for treatment[20]. However, the optimal surgical treatment for AT with a diameter greater than 6 cm is still controversial. However, some studies have successfully reported LA with a diameter of 10 cm [21]. The choice of a transperitoneal or retroperitoneal approach is mainly based on the preferences of the surgeon and the tumor situation. Compared to TPLA, RPLA has the advantages of less interference with abdominal organs and faster recovery, making it more widely performed by Chinese scholars[22]. When dealing with large AT with diameters greater than 6 cm, the TPLA approach has advantages such as a large operating space and clear anatomical location, making it widely applied in European and American medical centers[4]. There were 1059 patients with RPLA, 470 (88.0%) in the first stage and 589 (71.5%) in the second stage, indicating that the RPLA approach is the main surgical approach in our center. There were 145 (10.7%) patients with TPLA, and the number of patients increased from 8 (1.5%) in the first stage to 137 (16.6%) in the second stage. These findings have indicated that with the changing treatment concepts and increasing communication with the outside world, LA technology has currently diversified in our center.
In 2001, Horgan et al. [23] reported the world's first RALA surgery. Compared to traditional LA technology, RALA not only has advantages such as a 3D visual field, fine manipulation and less tremor but also has virtues including less intraoperative bleeding, fewer surgical complications and a shorter LOS[24]. Some scholars have considered that RALA has advantages in dealing with complex AT, such as large volume tumors (> 6 cm) and patients with obesity. Furthermore, RALA has reduced intraoperative conversion rates[25, 26]. It is undeniable that RALA has the drawbacks of more operation time and high medical costs[27, 28], which also affects its wide utilization in clinical practice. In 2016, our center conducted RALA. A total of 48 procedures were performed, including 8 (1.5%) on patients in the first stage and 40 (4.9%) in the second stage, which is much less than that carried out by various medical centers in both domestic and external countries[29, 30]. This may be related to the late introduction of RALA in our center, the relatively mature RPLA technology, and the relatively low economic level of the region where we are located.
There were limitations in this study. 1. As a single-center retrospective study, there may be bias in the research results. 2. This article did not discuss surgical efficacy. There was no analysis of surgery-related factors, such as body mass index (BMI), operation time, intraoperative bleeding, postoperative complications and prognosis.