The incidence of malignancy in neoplasms of the submandibular salivary gland.
Article Type: Clinical report
Subject: Parotid glands (Research)
Parotid glands (Diseases)
Salivary glands (Diseases)
Salivary glands (Research)
Tumors (Demographic aspects)
Tumors (Research)
Authors: Schoeman, B.J.
Clifford, S.D.
Pub Date: 11/01/2007
Publication: Name: South African Journal of Surgery Publisher: South African Medical Association Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2007 South African Medical Association ISSN: 0038-2361
Issue: Date: Nov, 2007 Source Volume: 45 Source Issue: 4
Topic: Event Code: 310 Science & research Canadian Subject Form: Tumours; Tumours
Geographic: Geographic Scope: South Africa Geographic Code: 6SOUT South Africa
Accession Number: 182036141
Full Text: Summary

Objective. To test the validity of the reported high incidence (50%) of malignancy in neoplasms of the submandibular salivary gland, and to compare it with that of the parotid gland.

Methods. This is a retrospective analysis of major salivary gland neoplasms in 127 patients who were treated between August 1988 and December 2004 (15 1/2 years) at Kalafong Hospital, Pretoria.

Results. All but 1 of the patients were black. There were 100 benign and 27 malignant tumours. Thirty tumours were in the submandibular gland, including 3 malignant tumours, i.e. 10%. Of 97 parotid gland tumours, 24 (24.7%) were malignant.

Conclusion. The 10% incidence of malignancy in neoplasms of the submandibular gland in our series is much lower than the 50% reported in the literature. We postulate that race (black ethnicity) is probably a factor in this low incidence.

Approximately 3-6% of head and neck neoplasms occur in the major and minor salivary glands. (1) The majority of these neoplasms arise in the parotid gland (70-80%), whereas 10-15% are found in the submandibular gland and 5-10% in the sublingual and minor salivary glands. (2,3) It is generally believed that there is a 50% incidence of malignancy in neoplasms of the submandibular salivary gland, (1-6) which is substantially higher than the 20-25% quoted for the parotid gland. (1-7)

We suspected that malignant tumours of the submandibular gland would be rare in our black patient population. A retrospective analysis was therefore conducted to ascertain the incidence of malignancy in neoplasms of the submandibular gland, and to compare it with that of the parotid gland.

Patients and methods

All patients presenting with major salivary gland neoplasms over a 15 1/2-year period (August 1988-December 2004) were included in the study. Patient data were extracted from the computerised database of the Department of Surgery, Kalafong Hospital. Final histological diagnoses of submandibular and parotid gland tumours were correlated with histopathological reports of resected specimens, or the occasional biopsy of locally advanced cancers. Neoplasms were classified into benign or malignant tumours, including various subtypes of each. The World Health Organization's histological classification of salivary gland tumours was used. (8)

Results

A total of 127 patients fitted the inclusion criteria for analysis, of which 126 were black patients. Only 1 patient was white, a female with cancer of the parotid gland. There were 100 benign and 27 malignant tumours in 55 male and 72 female patients, aged 16-86 years (mean 44.8) (Table I). Thirty tumours were in the submandibular salivary gland, including 3 malignant tumours (10%): 2 adenoid cystic carcinomas and 1 squamous cell carcinoma. The 27 benign tumours (90%) were all pleomorphic adenomas. Of 97 parotid gland tumours, 24 (24.7%) were malignant and 73 (75.3%) benign (Table II). Two patients in this group presented with locally recurrent tumours: 1 with carcinoma and 1 with pleomorphic adenoma.

Discussion

Our finding of a 10% incidence of malignancy in neoplasms of the submandibular salivary gland in black patients is at variance with the high incidence of 50% reported in the Western literature. (1-6) The reasons for this low incidence is not clear. Race or referral patterns may play a role, and our series might have been too small to be representative.

However, submandibular gland neoplasms are uncommon, as reflected by the 31 cases reported by Theron and Middlecote. (9) This series of 217 cases of salivary gland neoplasms was larger than ours, although they included 48 minor salivary gland tumours. Six of the 31 submandibular tumours were malignant, i.e. 19.4%, which is also much lower than the reported incidence. These 6 cancers included 2 mucoepidermoid carcinomas and 4 carcinomas of unspecified nature, while the 25 benign tumours consisted of 23 pleomorphic and 2 monomorphic adenomas.

The Bloemfontein series consisted of 124 black and 93 white patients. (9) Although the authors addressed the racial distribution of certain specific tumours, they did not give a racial breakdown of their 31 submandibular tumours. We suspect that the major portion of these would have occurred in blacks (B. D. Middlecote--personal communication, 2006). In Western literature quoted in this paper the race of patients is not mentioned. (1-6) We therefore assume that the vast majority of patients in these reports were white.

Possible referral bias of potentially malignant cases to a cancer hospital, viz. Memorial Sloan Kettering Cancer Center (MSKCC), may play a role in the high incidence of malignancy reported for the submandibular gland. (1,3) This factor does not seem to be applicable to the parotid gland, however, as the 25% incidence of malignancy reported by MSKCC1, (3) corresponds to ours (24.7%), and that of other general hospitals. (2,7,9)

To conclude, the 10% incidence of malignancy in neoplasms of the submandibular salivary gland in our series is much lower than that reported elsewhere. The 19.4% incidence in the Bloemfontein series supports this figure. We postulate that race (black ethnicity) is probably a factor in this low incidence of malignancy in the submandibular gland.

REFERENCES

(1.) Shah JP, Ihde JK. Salivary gland tumors. Curr Probl Surg 1990; 27(12): 775-843.

(2.) Califano J, Eisele DW. Benign salivary gland neoplasms. Otolaryngol Clin North Am 1999; 32(5): 861-873.

(3.) Spiro RH. Salivary neoplasms: Overview of a 35-year experience with 2,807 patients. Head and Neck Surgery 1986; 8: 177-184.

(4.) Lorenz RR, Netterville JL, Burkey BB. Salivary gland neoplasms. In: Townsend CM, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of Surgery. 17th ed. Philadelphia: Elsevier Saunders, 2004: 852-854.

(5.) Teknos TN. Salivary gland neoplasms. In: Greenfield LJ, ed. Surgery: Scientific Principles and Practice. 3rd ed. Philadelphia: Lippincott Williams & Wilkins, 2001: 650-652.

(6.) Smith WP, Langdon JD. Disorders of the salivary glands. In: Russell RCG, Williams NS, Bulstrode CJK, eds. Bailey and Love's Short Practice of Surgery. 24th ed. London: Arnold, 2004: 726.

(7.) Lakhoo K, Mannell A. Parotid tumours in black patients: The Baragwanath Hospital experience, 1981 - 1986. S Afr J Surg 1989; 27: 13-15.

(8.) Seifert G, Sobin LH. The World Health Organization's histological classification of salivary gland tumors. Cancer 1992; 70(2): 379-385.

(9.) Theron EJ, Middlecote BD. Tumours of the salivary glands: The Bloemfontein experience. S Afr J Surg 1984; 22: 237-242.

B. J. SCHOEMAN, M.B. CH.B., M.MED., F.C.S. (S.A.), F.R.C.S. (EDIN.)

S. D. CLiFFORD, M.B. CH.B., M.MED.

Department of Surgery, Kalafong Hospital and University of Pretoria, Pretoria
TABLE I. GENDER AND AGE OF PATIENTS

                  Male   Female   Mean age (yrs)
                                  (range)

Total cases       55     72       44.8 (16 - 86)
Submandibular tumour cases
  Malignant       2      1        43.4 (30 - 55)
  Benign          11     16       39.9 (16 - 78)
Parotid tumour cases
  Malignant       14     10       54.3 (20 - 86)
  Benign          28     45       43.5 (15 - 81)

TABLE II. DISTRIBUTION AND TYPE OF SALIVARY GLAND TUMOURS

                                        Parotid     Submandibular
                                         gland          gland

Malignant tumours
  Mucoepidermoid carcinoma             11
  Adenoid cystic carcinoma              3            2
  Acinic cell carcinoma                 4
  Malignant pleomorphic tumour          1
  Epithelial-myoepithelial carcinoma    1
  Squamous cell carcinoma               1            1
  Adenocarcinoma                        1
  Carcinoma, undifferentiated           1
  Lymphoma                              1
  Subtotal                             24 (24.7%)    3 (10%)

Benign tumours
  Pleomorphic adenoma                  66           27
  Warthin's tumour                      3
  Monomorphic adenoma                   2
  Cystadenoma                           1
  Myoepithelioma                        1
    Subtotal                           73 (75.3%)   27 (90%)
Total                                  97           30
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