Histopathologic Patterns Of Nasopharyngeal Malignancy In Lagos, Nigeria And Its Association With Epstein-Barr Virus (Ebv): A 10-Year Retrospective Study

Abstract Background: Nasopharyngeal cancer (NPC) is a rare cancer worldwide. It is now found to be increasing in incidence in Nigeria, though the incidence is lower when compared to countries in the Mediterranean basin, North Africa and Southeast Asia. NPC is frequently associated with Epstein-Barr virus (EBV), but no previous study has been done in Lagos to document the association. Objective: To determine the prevalence, histologic types and age distribution of nasopharyngeal malignancy in Lagos University Teaching Hospital (LUTH) and its association with EBV over a period of 10 years, between January 2003 to December 2012. Materials and Methods: Slides and formalin-fixed paraffin-embedded (FFPE) tissue blocks, hospital request forms, referral cards, patients’ case notes and duplicate copies of histopathology reports of cases of histologically diagnosed nasopharyngeal malignancy in the Anatomic and Molecular Pathology department of LUTH within the study period were retrieved. The cases were reclassified into epithelial and non-epithelial malignancies. The epithelial malignancies were reclassified according to WHO classification. Immunohistochemistry (IHC) for EBV latent membrane protein-1 (LMP-1) was carried out on cases with viable FFPE to evaluate the prevalence of the virus in Nasopharngeal malignancy. Results: A total of 75 histologically confirmed cases of nasopharyngeal malignancy were seen during the study period, which constituted 1.1% of the total cancer recorded in this center. There were 47 males (63%) and 28 females (37%) with a male to female ratio of 1.7:1. The age ranged from 3 to 75 years, mean age was 44.1 years, the peak age group was 40 -49 years for males and 50 - 59 years for females. On histological classification, undifferentiated carcinoma (WHO type III) was the commonest (49.3%), differentiated non-keratinizing squamous cell carcinoma, SCC (WHO type II) and keratinizing SCC (WHO type I) accounted for 24% and 9.3% respectively. Thus, NPC accounted for 82.6% of the total cases of nasopharyngeal malignancy seen. Other histological types seen were non-Hodgkin lymphoma (NHL) 13.3%, well differentiated adenocarcinoma 2.7% and low grade mucoepidermoid carcinoma 1.3%. EBV LMP-1 IHC was positive in 30 (86%) out of the 35 cases studied. These consisted of 14 undifferentiated carcinoma, 5 NHL, 2 adenocarcinoma, 7differentiated non-keratinizing SCC (WHO type II) and the 2 cases of keratinizing SCC (WHO type 1). Conclusion: Nasopharyngeal malignancy is not uncommon in this environment. It occurred more frequently in males than females with the peak age of incidence at 5th decade of life, undifferentiated carcinoma (WHO type III) is the commonest histologic type and it is highly associated with EBV. Note: This abstract was not presented at the meeting. Citation Format: Oladipo Omoseebi, Olakanmi Akinde, Omobolade Obadofin, Nzechukwu Ikeri, Gabriel Ogun, Adekumbiola Banjo. Histopathologic patterns of nasopharyngeal malignancy in Lagos, Nigeria and its association with Epstein-Barr virus (EBV): A 10-year retrospective study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5759. doi:10.1158/1538-7445.AM2017-5759