Abstract
There is little information in the English-language literature about the epidemiology of salivary gland neoplasms in the eastern Chinese population. A large retrospective study (6982 primary salivary tumors during 23 years) was carried out to investigate the clinicopathological features (tumor location, patient sex and age) of these tumors in this population. 3593 tumors were in males and 3389 in females. Pleomorphic adenoma (69%) was the most common tumor and 20% were located in minor glands. 92% of Warthin’s tumors occurred in males. Malignant tumors were predominantly adenoid cystic carcinoma (30%) and mucoepidermoid carcinoma (30%). Incidences of lymphoepithelial carcinomas (5%) and polymorphous low-grade adenocarcinoma (1%) of malignant tumors were identified. 28% of tumors originated from minor glands. Most findings were similar to those in the literature, with some variations. The salivary tumors slightly predominated in males. Relatively higher incidences of minor gland tumors and specifically of pleomorphic adenoma in minor glands were noted. Adenoid cystic carcinoma and mucoepidermoid carcinoma constituted the most common malignancies. There was a high incidence of lymphoepithelial carcinomas but a low incidence of polymorphous low-grade adenocarcinoma. The historical significant male predominance of Warthin’s tumor was confirmed.
Salivary gland tissues are distributed widely in the upper aerodigestive tract. The major salivary glands are the parotid, submandibular and sublingual glands. Minor salivary glands are present in many sites, such as the lips, gingiva, cheek, palate, tongue, oropharynx, paranasal sinuses and parapharyngeal space. Neoplasms originating from salivary glands comprise about 3–6% of all head and neck tumors, with an estimated global incidence of 0.4–13.5 per 100,000 persons annually . In China, salivary gland tumors account for only about 2% of human tumors , and malignant salivary gland tumors represent about 5% of all malignant tumors in the head and neck region, with an incidence of 1.0 per 100,000 persons per year. Salivary gland neoplasms are relatively rare in China, but the three major paired salivary glands and hundreds of minor salivary glands located within the submucosa can give rise to a wide range of neoplasms, forming one of the most heterogeneous groups of histopathology.
The site, patient age and sex distributions of different salivary gland neoplasms vary with race, histological type and geographic location . There are discrepancies in the incidence of salivary gland tumors between different geographic areas and ethnic groups . A survey of different ethnic groups in Malaysia showed a higher frequency of salivary gland tumors in Malays than in Chinese and Indians . Many studies of the distribution of tumor site, patient age and sex have dealt with tumors presenting within the parotid gland or major or minor glands . To the authors’ knowledge, there are few reports in the English literature on salivary gland tumors in the eastern Chinese population. The aim of this study was to analyze the relative frequency, location, patient sex and age of a variety of histological tumors of the oral and maxillofacial region in the eastern Chinese population over 23 years.
Patients and Methods
This study included patients with primary epithelial salivary gland neoplasms who, during the 23-year period between 1985 and 2007, underwent operations in the Department of Oral and Maxillofacial Surgery, Ninth People’s Hospital, Shanghai Jiao Tong University, School of Medicine in the east of China.
Hematoxylin-eosin stained slides (and immunostained sections if necessary) of all cases were reviewed and reclassified by three pathologists based on the World Health Organization (WHO) Pathology and Genetics of Head and Neck Tumors (2005) criteria . The data were analyzed for their distribution of patient’s sex and age and anatomical location of presentation.
Results
Histological Types
6982 patients underwent operations for salivary gland tumors during the specified period. Of these tumors, 4743 (68%) were benign and 2239 (32%) were malignant. The ratio of benign tumors to malignancies was 2.12:1. The distribution of histological patterns by anatomical locations for benign and malignant salivary tumors are shown in Tables 1 and 2 , respectively.
| Major glands (n) | Minor glands (n) | Total ( n ) (%) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Parotid | Sub-mandibular | Sub-lingual | Floor of mouth | Palatal | Lips | Buccal | Larynx | Lingual | Gingival | Retro-molar | ||
| Pleomorphic adenoma | 2126 | 479 | 4 | 2 | 508 | 73 | 66 | 12 | 4 | 5 | 2 | 3281 (69.18) |
| Warthin’s tumor | 957 | 4 | 961 (20.26) | |||||||||
| Basal cell adenoma | 248 | 2 | 5 | 255 (5.38) | ||||||||
| Myoepithelioma | 119 | 3 | 47 | 2 | 1 | 2 | 174 (3.67) | |||||
| Cystadenoma | 17 | 1 | 1 | 1 | 4 | 1 | 2 | 1 | 28 (0.59) | |||
| Oncocytoma | 22 | 1 | 23 (0.48) | |||||||||
| Ductal papillomas | 1 | 5 | 1 | 3 | 10 (0.21) | |||||||
| Sebaceous lymphadenoma | 4 | 4 (0.08) | ||||||||||
| Canalicular adenoma | 2 | 1 | 3 (0.06) | |||||||||
| Sebaceous adenoma | 2 | 2 (0.04) | ||||||||||
| Nonsebaceous lymphadenoma | 2 | 2 (0.04) | ||||||||||
| Total (n) (%) | 3500 (73.79) | 490 (10.33) | 4 (0.08) | 2 (0.04) | 566 (11.93) | 76 (1.60) | 72 (1.52) | 13 (0.27) | 12 (0.25) | 6 (0.13) | 2 (0.04) | 4743 |
| Major glands (n) | Minor glands (n) | |||||||
|---|---|---|---|---|---|---|---|---|
| Parotid | Submandibular | Sublingual | Floor of mouth | Palatal | Lingual | Buccal | Gingival | |
| Adenoid cystic carcinoma | 79 | 74 | 50 | 67 | 209 | 68 | 36 | 11 |
| Mucoepidermoid carcinoma | 182 | 28 | 11 | 25 | 214 | 50 | 51 | 27 |
| Carcinoma ex pleomorphic adenoma | 98 | 27 | 40 | 3 | 1 | |||
| Acinic cell carcinoma | 137 | 7 | 2 | 1 | 11 | 2 | 5 | |
| Adenocarcinoma, NOS*** | 52 | 6 | 4 | 4 | 27 | 10 | 5 | 10 |
| Lymphoepithelial carcinoma | 94 | 12 | 2 | 1 | 9 | 1 | ||
| Myoepithelial carcinoma | 21 | 6 | 1 | 14 | 1 | 5 | 3 | |
| Epithelial-myoepithelial carcinoma | 21 | 1 | 9 | 1 | 1 | |||
| Squamous cell carcinoma | 29 | 7 | ||||||
| Cystadenocarcinoma | 14 | 1 | 1 | 3 | 2 | 3 | 2 | |
| Polymorphous low-grade adenocarcinoma | 2 | 20 | 7 | 1 | ||||
| Large cell carcinoma | 8 | 1 | 1 | 5 | 1 | 2 | 3 | |
| Clear cell carcinoma | 1 | 1 | 10 | 3 | 2 | |||
| Basal cell adenocarcinoma | 13 | 2 | ||||||
| Mucinous adenocarcinoma | 1 | 1 | 1 | 1 | 4 | |||
| Salivary duct carcinoma | 3 | 2 | 1 | 1 | ||||
| Sebaceous carcinoma | 4 | 1 | ||||||
| Small cell carcinoma | 1 | |||||||
| Oncocytic carcinoma | 3 | |||||||
| Sialoblastoma | 1 | |||||||
| Total (n) (%) | 764 (34.12) | 173 (7.73) | 71 (3.17) | 103 (4.60) | 572 (25.55) | 145 (6.48) | 116 (5.18) | 63 (2.81) |
| Minor glands (n) | ||||||||
|---|---|---|---|---|---|---|---|---|
| Jaw | Sinus maxillaris | Retro-molar | Lips | Larynx | External auditory canal | Others | Total ( n ) (%) | |
| Adenoid cystic carcinoma | 37 | 35 | 4 | 8 | 2 | 1* | 681 (30.42) | |
| Mucoepidermoid carcinoma | 38 | 5 | 29 | 11 | 2 | 673 (30.06) | ||
| Carcinoma ex pleomorphic adenoma | 4 | 2 | 2 | 1 | 1** | 179 (7.99) | ||
| Acinic cell carcinoma | 4 | 2 | 2 | 1 | 174 (7.77) | |||
| Adenocarcinoma, NOS | 3 | 7 | 4 | 1 | 1 | 1 | 1**** | 136 (6.07) |
| Lymphoepithelial carcinoma | 2 | 121 (5.40) | ||||||
| Myoepithelial carcinoma | 4 | 1 | 56 (2.50) | |||||
| Epithelial-myoepithelial carcinoma | 1 | 1 | 1 | 36 (1.61) | ||||
| Squamous cell carcinoma | 36 (1.61) | |||||||
| Cystadenocarcinoma | 3 | 2 | 1 | 32 (1.43) | ||||
| Polymorphous low-grade adenocarcinoma | 1 | 31 (1.38) | ||||||
| Large cell carcinoma | 21 (0.94) | |||||||
| Clear cell carcinoma | 1 | 1 | 19 (0.85) | |||||
| Basal cell adenocarcinoma | 15 (0.67) | |||||||
| Mucinous adenocarcinoma | 1 | 9 (0.40) | ||||||
| Salivary duct carcinoma | 7 (0.31) | |||||||
| Sebaceous carcinoma | 5 (0.22) | |||||||
| Small cell carcinoma | 2 | 1 | 4 (0.18) | |||||
| Oncocytic carcinoma | 3 (0.13) | |||||||
| Sialoblastoma | 1 (0.04) | |||||||
| Total (n) (%) | 93 (4.15) | 50 (2.23) | 44 (1.97) | 30 (1.34) | 9 (0.40) | 3 (0.13) | 3 (0.13) | 2239 |
Pleomorphic adenoma (PA) was the most common tumor and accounted for 69% (3281/4743) of all benign tumors, followed by Warthin’s tumor (961/4743, 20%). Basal cell adenoma and myoepithelioma accounted for 5% (255/4743) and 4% (174/4743) of benign tumors, respectively, followed by cystadenoma (0.6%, 28/4743), oncocytoma (0.5%, 23/4743) and ductal papillomas (0.2%, 10/4743). Sebaceous and nonsebaceous lymphadenoma, canalicular adenoma, and sebaceous adenoma were rare, each accounting for less than 0.1% of benign tumors ( Table 1 ).
Of the 2239 malignancies, adenoid cystic carcinoma (ACC, 681/2239, 30%) and mucoepidermoid carcinoma (MEC, 673/2239, 30%) were the most common histological types, followed by carcinoma ex pleomorphic adenoma (179/2239, 8%), acinic cell carcinoma (174/2239, 8%), adenocarcinoma, not otherwise specified (136/2239, 6%) and lymphoepithelial carcinoma (LEC, 121/2239, 5%). Myoepithelial carcinoma (56/2239, 3%), epithelial-myoepithelial carcinoma (36/2239, 2%), squamous cell carcinoma (36/2239, 2%), cystadenocarcinoma (32/2239, 1%), polymorphous low-grade adenocarcinoma (PLGA, 31/2239, 1%), and large cell carcinoma (21/2239, 1%) were rare. The remaining cases included, in descending frequency, 19 (0.9% of malignancies) clear cell carcinomas, 15 (0.7%) basal cell adenocarcinomas, 9 (0.4%) mucinous adenocarcinomas, 7 (0.3%) salivary duct carcinomas, 5 (0.2%) sebaceous carcinomas, 4 (0.2%) small cell carcinomas, 3 (0.1%) oncocytic carcinomas, and 1 (0.04%) sialoblastoma. There were no cases of carcinosarcoma, sebaceous lymphadenocarcinoma, low-grade cribriform cystadenocarcinoma, or metastasizing pleomorphic adenoma in this series ( Table 2 ).
Locations
Most of the salivary gland tumors (5002/6982, 72%) originated from the three major salivary glands. The rest (1980/6982, 28%) originated from minor glands sited in the palate, cheek and lips.
Among the three paired major glands, more than three-fifths of salivary tumors involved the parotid gland (4264/6982, 61%), which was the most common site both in benign (3500/4743, 74%) and malignant (764/2239, 34%) tumors ( Fig. 1 ). There were about 4.6 times as many benign parotid tumors (3500/4264, 82%) as malignant ones (764/4264, 18%). The submandibular gland was the third most common site of involvement among all salivary gland tumors (663/6982, 10%), and there were about 2.8 times as many benign submandibular tumors (490/663, 74%) as malignant ones (173/663, 26%). In contrast, in the sublingual gland (75/6982, 1%), there were only 4 benign tumors involved and 95% (71/75) of sublingual tumors were malignant.
