Salivary gland tumours: A 16-year review at Jos University Teaching Hospital, Jos

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1 Salivary gland tumours: A 16-year review at Jos University Teaching Hospital, Jos 1 EC Otoh, 2 BM Mandong, 1 IS Danfillo, 1 PH Jalo 1 Regional Center for Oral Health Research and Training Initiatives (RCORTI), Jos, Nigeria 2 Department of Histopathology, Jos University Teaching Hospital (JUTH), Jos, Nigeria Correspondence: Dr. Emmanuel Chukwuka Otoh Basic Science & Research Division Regional Centre for Oral Health Research & Training Initiatives (RCORTI) for Africa 3, CBN Road, PMB 2067 Jos, Plateau State, Nigeria Tel: / / / Fax: ecotoh@yahoo.co.uk Key words: salivary gland, neoplasia, radiation, pleomorphic adenoma, Nigeria SUMMARY There is a dearth of information on the history of salivary gland tumours in northern Nigeria and the objective of this study is to document the epidemiology of salivary gland tumours as seen at the Jos University Teaching Hospital (JUTH), Jos, Plateau State, Nigeria. It is designed as a retrospective study and made use of the duplicate histology reports and case notes of all reported cases of salivary gland tumours seen at the JUTH over a period of 16 years which were retrieved from the histopathology department of the hospital. Information on sociodemographic characteristics, histological type and relevant clinical parameters were extracted and entered for data analysis using the Brititsh Association of Head & Neck Oncologists (BAHNO) Minimum Dataset for Cancers. A total of 117 cases of histologically confirmed salivary gland tumours were seen during the period. The benign-malignant ratio was 2.7:1 and the parotid gland was the most affected site (52.1%). Pleomorphic adenoma (89.4%) and mucoepidermoid carcinoma (22.6%) respectively, were the most common benign and malignant tumours reported. Mucoepidermoid carcinoma occurs commonly between the 2 nd and 5 th decades of life with no gender predilection while pleomorphic adenoma Volume 1 Number

2 occurs usually between the 2 nd and 3 rd or 4 th decades of life; with a fairly equal gender distribution (M : F= 1 : 1.2). Although there were greater delays in the presentation of benign cases (30.4 ± 24.2 months) in comparison with malignant cases (12± 6.9 months), the difference was not statistically significant (p=0.09). INTRODUCTION Geographical variations in the prevalent site and type of salivary gland tumours have been reported in the literature. 1-6 The commonly involved sites include the parotid and sub-mandibular glands and the minor salivary glands of the palate, with the sublingual gland being the least affected. 2,3,5,6 The commonly reported tumours (benign and malignant) include pleomorphic adenoma, mucoepidermoid carcinoma, adenocystic carcinoma, carcinoma ex-pleomorphic adenoma and adenocarcinoma. 4,5,7,8,9,10 Studies in Nigeria and Africa showed that salivary gland cancers constitute between 2.8% and 10% of all head and neck malignancies. 1,2,5,9 Certain risk factors, like radiation exposure, have been associated with the development of malignant salivary gland tumours. 11 Most studies in Africa showed a delay by patients in reporting to the hospital, with most presenting with the late stage disease (stage III/IV), whereas early reporting in developed countries has greatly improved the survival of patients diagnosed with these tumours. 1,5,6,10,12,13 An earlier study of salivary gland tumours in northern Nigeria decried the poor record of the natural history of tumours in northern Nigeria due to the long distances patients had to travel for treatment and loss of patients to follow up. 8 The commencement of histopathology services at JUTH in 1986 was expected to increase the number of referrals for biopsy from the areas in north central Nigeria served by the hospital. This study documents the epidemiology of salivary gland neoplasia in the areas served by the hospital. METHOD JUTH is one of the referral hospitals for histopathology in the North Central Zone of Nigeria and receives biopsy samples from both public and private hospitals in the North Central Zone (Plateau, Nassarawa, Benue, Kogi states and some states in the North Eastern Zone (Bauchi and Taraba states), with an approximate population of about 14 million. The ethical clearance for the study was obtained from the Ethical Committee of JUTH. Only histologically diagnosed salivary and extra-salivary gland tumours were included in the study. Socio-demographic information and history of patient management (age, sex, occupation, ethnic group, history of habits; history of symptoms, dates of referral and 1 st appointment, pre-treatment and histological TNM staging of lesion, clinical and histological diagnosis, dates of biopsy and dates of biopsy report; definitive treatments and date of discharge) were retrieved from pathology and medical records of patients from January 1987 (the commencement of histopathological services at JUTH) until December 2002 were reviewed. The information obtained were entered into data entry forms designed and modified according to the pattern developed for the British Association of Head and Neck Oncologists (BAHNO) Minimum Dataset. 14 The tumours recorded were as classified by the 3 rd Edition of the International Classification of Diseases Oncology (ICD-O). 15 The information was analyzed statistically using the Microsoft Office 2000 Excel Package; SPSS 11+ and the STATCALC R statistical package of the Epi Info Version 6.0 (1993). The student s t test, Yates corrected, and Fisher s exact tests were used to determine areas of significant associations between nominal variables such as prevalence rate and duration of symptoms and to compare means in this study with the reported findings from previous studies. A p-value of 0.05 or less was considered significant. RESULTS A total of 117 cases of histologically diagnosed salivary and extra-salivary gland tumours were seen during the period of study with a benign-malignant ratio of 2.7:1. Of these 117 tumours, 85 (72.6%) were benign, while 32 (27.4%) were malignant. Plemorphic adenoma (89.4%) was the most common benign tumour and muco-epidermoid carcinoma (18.6%) the most common malignant tumour seen. The prevalence of other tumours is as shown in table Volume 1 Number

3 The major salivary glands (67.5%), especially the parotid gland (52.1%), were the most affected sites. The intra-oral minor salivary glands were less affected (5.1%), with the palate and unspecified intra-oral glands constituting 1.7% each. No malignancy was reported in any minor salivary gland site (table 1). The age and sex distribution at presentation among the patients presenting with salivary and extrasalivary gland tumours is shown in table 2. The mean age at presentation was 34.2 ± 19.0 years with a range of 5-90 years. Majority of the benign tumours (58.8%) occurred during the 2 nd -4 th decades of life with a malefemale ratio of 1 : 1.2. Pleomorphic adenoma was more commonly reported in the 2 nd and 3 rd decades of life, with a peak in the 2 nd decade (table 2). Its overall mean age of occurrence was ± 15.3 years (males = 31.9 ± 18.2 years; females = 28.4 ± 12.5 years). Malignant tumours occurred most commonly in the 4 th -5 th decades of life with an equal sex distribution. Mucoepidermoid carcinoma was reported commonly in the 2 nd and 5 th decades of life, with an overall mean age of occurrence of 36 ± 14.4 years (males = 29.3 ± 15.3 years; females = 6 ± 5.7 years) (table 2). The duration of symptoms is defined in this study as the interval between the onset of symptoms and the date of reporting at the hospital. Patients with benign tumours of the major salivary glands delayed about 2.5 times longer than those with malignant lesions (p=0.09). Specifically, patients diagnosed with pleomorphic adenoma delayed for twice as long as the patients diagnosed with its malignant variant (table 3). DISCUSSION The ratio of benign to malignant tumours is relatively higher (p>0.05) than previously reported for Nigeria and Tanzania 1,2,5,10 (see table 4). Table 1. Salivary gland tumours by ICD-O codes Tumours Major Salivary Glands Minor Salivary Glands Unspecified glands Parotid Submnd Subling Palate Lip Mouth Extra-SG Tonsils Total No. (%) Pleomorphic adenoma * (64.9)* Monomorphic adenoma (2.6) Warthin s tumour (1.7) Volume 1 Number

4 Schwannoma (0.85) Cavernous lymphangioma (0.85) Cavernous hemangioma (0.85) Lymphangioma (0.85) Mucoepidermoid carcinoma (5.9) Adenoidcystic carcinoma (4.3) Squamous cell carcinoma (2.5) Acinic cell tumour (3.4) Ca. Ex Pleomorphic adenoma (3.4) Adenocarcinoma (0.85) Adenolympho carcinoma (0.85) Undiff. carcinoma (1.7) Unspecified carcinoma (2.5) Lymphoepithelioma (0.85) Non Hodgkin s lymphoma (0.85) TOTAL (%) 61 (52.1) 17 (14.4) 1 (0.85) 2 (1.7) 1 (0.85) 2 (1.7) 4 (3.4) 1 (0.85) 28 (23.7) 117 (100) * Includes 4 cases in other minor salivary gland sites like the Eye (2), Max. Antrum (1) and Neck (1) Table 2a. Age and gender distribution of salivary gland tumours benign tumours Age group Pleomorphic adenoma Monomorphic adenoma Other benign tumours Total Sex Age Male Female Gender not specified Male Female Male Female Unspecified adult Unspecified age Total Table 2b. Age and gender distribution of salivary gland tumours malignant tumours Age group Mucoepidermoid carcinoma Adenoidcystic carcinoma Other malignant neoplasms Total Sex M F U M F U M F Age Volume 1 Number

5 Unspecified adult Unspecified age Total Table 3. Duration of symptoms by site and tumour type Site Histological type Duration of symptoms (months) All salivary glands benign 30.4 ± 24.2 malignant 12 ± 6.9 Parotid gland benign 27.3 ± 28.2 malignant 12 ± 6.9 Submandibular gland benign 30 ± 20.8 malignant Minor salivary glands benign 42 ± 25.5 malignant Tumours Duration of symptoms (months) Pleomorphic adenoma 32.1 ± 24.5 Carcinoma. ex pleomorphic adenoma 16.3 ± 7.1 Relative to head and neck cancers, the 4.4% prevalence of malignant salivary gland tumours in this study is lower (p<0.05) than the 10% and the 11% previously reported for Lagos and Maiduguri respectively (table 5). The variations could be attributed to the varying inclusion criteria for tumours in the Lagos study and the lack of maxillofacial surgery facilities at Jos. 1,16 The prevalence of pleomorphic adenoma among benign tumours agrees with the previously reported findings in Nigeria and East Africa. 1,5,10 The pattern of salivary gland malignancies in northern Nigeria has shifted from a prevalent adenocystic carcinoma in the pre-1980 period to a currently prevalent muco-epidermoid carcinoma in Jos and Maiduguri. 8,16,17 The prevalence of mucoepidermoid carcinoma (5.9%) in this study is similar to previously reported rates from Nigeria, but contrasts with the findings in Tanzania (p<0.05) that reported a 24.8% prevalence of adenocystic carcinoma. 5 Beal and others in a study to establish a relationship between radiation exposure and salivary gland tumours, suggested an increased risk for developing secondary malignant (versus benign) after radiation exposure, with the mucoepidermoid carcinoma being the most implicated malignancy. 11 There is the need for further research into such a possibility among patients that have had radiotherapy for various forms of head and neck cancers in Nigeria. The prevalence of tumours in the parotid gland in this study is similar to cases in other studies. However, the occurrence of tumours in minor glands is significantly lower (p = ) than in previously reported studies in northern Nigeria. 8,16 The occurrence of cases of salivary gland malignancies in patients aged 40 years and below in this and other Nigerian studies is higher than reported for most Western countries (p<0.05). This could be attributed to the early diagnosis and advanced referral system in the developed countries and the possible exposure to risk factors associated with the development of these malignancies. 6,16 The late stage at presentation of patients with malignancies agrees with the pattern reported for salivary gland and other head and neck cancers in Nigeria and parts of Africa, but contrasts significantly with findings in Western countries. 1,5,6,16-18 This could be attributed to delayed reporting because of the painless and slow-growing nature of most salivary Volume 1 Number

6 gland tumours, until it has reached a size when it either constitutes a social embarrassment 5 or like the adenocystic carcinoma, results in painful neurological symptoms following peri-neural invasion. 19 Expectedly, the survival of patients with malignancies would be relatively low, considering the late stage at presentation, but different studies have shown that individual differences exist with respect to different malignancies. It has been reported in studies in Europe and America that while the tumour size, peri-neural invasion and margin status (staging characteristics) influence the local control of adenocystic carcinoma, the tumour grade and stage are less important than previously described in the survival of patients with mucoepidermoid carcinoma. 13,19,20 CONCLUSION Pleomorphic adenoma and mucoepidermoid carcinoma were the most common benign and malignant tumours reported in Jos and the parotid gland most common site affected. The late stage at presentation of patients with malignancies is attributable to delayed reporting because of the painless and slow-growing nature of most salivary gland tumours, until it has reached a size when it either constitutes a social embarrassment or results in painful neurological symptoms. ACKNOWLEDGEMENTS The fund for this research was provided by a grant from the Regional Centre for Oral Health Research and Training Initiatives (RCORTI) for Africa, Jos, Nigeria. Our sincere appreciation goes to the management, the heads of the Histopathology and Medical Records Departments and the Cancer Registry Manager of the Jos University Teaching Hospital for their approval and kind contributions in the retrieval of the required data. REFERENCES 1. Arotiba GT. Salivary gland neoplasms in Lagos, Nigeria. WAJM 1996 Jan-Mar; 15(1): Kolude B, Lawoyin JO, Akang EE. Salivary gland neoplasms: a 21-year review of cases seen at the University College Hospital, Ibadan. Afr J Med Med Sci 2001; 30(1-2): Sousa J, De Sa O. Salivary gland tumours: an analysis of 62 cases. Indian J Cancer 2001; 38(1): Jansisyanont P, Blanchaert RH, Ord RA. Intraoral minor salivary gland neoplasms: a single institution experience of 80 cases. Int J Oral Maxillofac Surg 2002; 31(3): Masanja MI, Kalyanyama BM, Simon EN. Salivary gland tumours in Tanzania. East Afr Med J 2003; 80(8): Hyam DM, Veness MJ, Morgan GJ. Minor salivary gland carcinoma involving the oral cavity or oropharynx. Aust Dent J 2004; 49(1): Batsakis JG. Clinical pathology of oral cancer. In: Shah JP, Johnson NW, Batsakis JG, eds. Oral Cancer. Pp London :Martin Dunitz Publication, Adekeye EO, Robertson JM. Salivary gland tumours in Northern Nigeria. Trop Doct 1979 Oct; 9(4): Abiose BO, Oyejide O, Ogunniyi J. Salivary gland tumours in Ibadan, Nigeria: a study of 295 cases. Afr J Med Med Sci 1990 Sept; 19(3): Ezeanolue BE. Salivary Gland Neoplasms. A descriptive analysis of the pattern in Enugu. WAJM 1999; 18: Beal KP, Singh B, Kraus D, Yahalom J, Portlock C, Wolden SL. Radiation-induced salivary gland tumours: a report of 18 cases and a review of the literature. Cancer J 2003; 9(6): Olasoji HO, Pindiga UH, Ugboko VI, Arotiba GT. A clinicopathologic study of soft tissue tumours of the palate in Nigerians. The National Postgraduate Medical Journal 1999; 6(3): Kokemueller H, Eckardt A, Brachvogel P, Hausamen JE. Adenoidcystic carcinoma of the head and neck a 20 years experience. Int J Oral Maxillofac Surg 2004; 33(1): Wight R. BAHNO National Minimum and Advisory Head and Neck Data Sets. Version1.0. London: Fritz A, Percy C, Jack A, Shanmugaratnam K, Sobin L, Parkin DM, Whelan S eds. International Classification of Diseases for Oncology. 3 rd Edition. Geneva: Otoh EC, Johnson NW, Danfillo IS, Adeleke OA, Olasoji HO. Primary head and neck cancers in North Eastern Nigeria. WAJM 2004; 23(4): Otoh EC, Johnson NW, Mandong BM, Danfillo IS, Jalo PH. Primary head and neck cancers in Jos, Nigeria: A Re-visit. [WAJM press 2004]. 18. Oji C. Late presentation of orofacial tumours. J Craniomaxillofac Surg 1999; 27: Marsh WL, Allen MS. Adenoidcystic carcinoma: biologic behaviour in 38 patients. Cancer 1979; 43: Boahene DK, Olsen KD, Lewis JE, Pinheiro AD, Pankratz VS, Bagniewski SM. Mucoepidermoid carcinoma of the parotid gland: the mayo clinic experience. Arch Otolaryngol Head Neck Surg 2004; 130 (7): Volume 1 Number

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