Anhui is located in the southeastern province of China, covering 140,100 square kilometers with a population of 61.13 million. Hefei is the capital and central region of the Anhui Province, with a permanent resident population of 9.3699 million. Fuyang is the largest northern central city of Anhui Province, with a permanent resident population of 8.171 million. Wuhu is the regional center of southern Anhui Province, with a permanent resident population of 3.672 million. Many patients with parotid gland tumors are treated in the largest comprehensive hospitals in each region. This provided a population to evaluate epidemiological and pathological features of parotid gland tumors in the Anhui province of China.
This study observed a slight female predilection among the 758 patients with parotid tumors in the Anhui province, consistent with other findings11,12,13,14. However, other studies concluded that parotid gland tumors were more common in males, which could be due to regional differences15,16. In the current study, the ages of the patients ranged from 14 to 90 years (mean, 50.77 years). The age group of benign tumors with the highest incidence was 51–60 years old in both men and women, which was similar to previous reports15,17. Furthermore, there were more cases of women in their 30s and 40s than men, which may be due to the gender characteristic of benign tumors17.
Based on the histopathological data, 84.6% of the parotid gland tumors were benign tumors in this group, which was higher than the rates reported by authors in the UK, Brazil, Shanghai, and the Sichuan region of China15. All reports suggested benign tumors were predominant in parotid gland tumors. Comparing the incidence between the three hospitals, PAs were the most common benign tumors varying from 40.82% in Wuhu to 51.85% in Hefei, consistent with previous literature5. This study showed that the second most common benign tumor were WTs, similar to earlier demographic studies12,18,19. BCA was found to be the third most common benign tumor in Hefei and Fuyang. However, the third most common benign tumor in Wuhu was MEC, which was much higher than BCA. This trend may be characteristic of the disease distribution in Wuhu.
In this study, a large female predilection was observed in cases of PA. Pseudopodia were also found in pathological sections of the PAs, which was recognized as the infiltration of neoplastic cells into the capsule20. PAs are a tumor with a wide range of histopathological features that typically exhibit various cell types, including round, angular, oval, and plasmacytoid cells with a duct-like space dominated by fibrous and mucoid stroma21. Squamous metaplasia and incomplete capsules were common, whereas other features such as vascular invasion, crystals, and psammoma bodies were less common. Zbären and Stauffer22observed that 48% of 218 cases of parotid PAs had features of pseudopodia and/or satellite nodules, with a higher incidence in classical subtypes. The high rate of tumor infiltration into encapsulated tissue may be a risk factor for recurrence, especially after surgical resection, as tumor tissue within the capsule may remain at the surgical site23. This is the theoretical basis of superficial parotidectomy in cases with PA20.
In this study, WT accounted for 18.4% of benign tumors, which was less than the prevalence in parts of Pennsylvania per one study. WT showed a significant gender difference, with a male-to-female ratio of 15.86:1. The prevalence in males was significantly more than in females, which was higher compared to previous literature24. Some literature showed a relationship between smoking and WT. There were a few female tobacco users in the WT group; however, we did not further explore this relationship. But the historically significant male predilection of WT was confirmed.
The present study showed that the most common malignant tumor of the parotid gland was MEC, varying from 18.75–35%, which was consistent with previous reports of global prevalence14,17,25,26. The second most common malignant tumor was ACC accounting for 20% of all malignant tumors in all centers except Hefei, where the second most common malignant tumor was SCC. We found that the prevalence of SCC was higher than that of other regions, which was inconsistent with other reports 19. Lee et al reported that the most frequent malignant tumor in the parotid gland was SCC (30%), which was considered to be the epidemiologic distribution of parotid gland tumor in the Chumnam area of Korea27.
High-grade solid MEC and SCC are pathologically confusing and susceptible to the subjective influence of pathologists. In our study, the prevalence of MEC in Hefei was lower than in the other two centers. We speculated that this result was related to the aspect of pathological diagnosis. The third most common tumors were AdCC and ACC in Hefei and ACC in Fuyang and Wuhu. Some studies report that ACC is the fifth most common malignant parotid gland tumor13. In fact, the variability in different pieces of literature about the prevalence of ACC may result from small and unicentric cohorts, perhaps due to geographic characteristics.
Understanding the epidemiological and histopathological characteristics of parotid gland tumors in the Anhui Province is crucial for better diagnosing these diverse and complex tumors and serving as an epidemiological baseline for diagnosing patients in this area.
Limitations
Due to the multi-institutional retrospective setting, we should consider the selection bias from three hospitals. Finally, the results may be limited by documentation.