|Year : 2019 | Volume
| Issue : 1 | Page : 38-41
Nasopharyngeal cancer in Kano – A histo pathologic review
Ochicha Ochicha, Abdullahi M Ahmad
Department of Pathology, Aminu Kano Teaching Hospital, Kano, Nigeria
|Date of Web Publication||5-Mar-2019|
Dr. Abdullahi M Ahmad
Department of Pathology, Aminu Kano Teaching Hospital, Kano
Source of Support: None, Conflict of Interest: None
Background: Nasopharyngeal cancer (NPC) represents the most common head and neck malignancy in most Nigerian centers. Although it is uncommon among all cancers, it has significant morbidity and mortality associated with it. There has been no specific study on NPC in our locality. This review, therefore, endeavors to document and evaluate the pattern in our center. Materials and Methods: This was a retrospective review of all nasopharyngeal cases diagnosed at the pathology department of our hospital between 1st January 2005 and 31st December 2014. The biodata and histopathological findings were reviewed. Results: NPC accounted for 1.3% of all cancers during the study period and was twice as common in males than females (M: F = 2.1:1). Patients' age ranged from 16 to 70 years with median of 38 years and bimodal peaks in the 3rd and 5th decades. Squamous carcinoma was the most frequent histologic type (97.1%), followed by adenoid cystic and papillary adenocarcinoma each comprising 1.4%. The prevalent squamous carcinoma subtypes were non-keratinizing (80%) and keratinizing (17%). Conclusion: Our findings were broadly similar to other Nigerian centers, but slightly at variance with other low incidence zones in Western world.
Keywords: Head and neck cancer, nasopharyngeal carcinoma, Nigeria
|How to cite this article:|
Ochicha O, Ahmad AM. Nasopharyngeal cancer in Kano – A histo pathologic review. Niger J Basic Clin Sci 2019;16:38-41
| Introduction|| |
Globally, nasopharyngeal cancer (NPC) is the 24th most common malignancy, accounting for 0.7% of the global cancer burden. The incidence shows striking geographic variation, with the highest rates in Southern China and North Africa; while rates are low in the Western world (Europe, North America).
Published studies from sub-Saharan Africa are few but indicate low prevalence., In Nigeria, although several studies report it as the most common head and neck cancer,, the incidence appears to be low.
Squamous carcinoma is overwhelmingly the most frequent histologic type. In addition, this has been strongly associated with Epstein-Barr virus infection, which is present in over 90% of nasopharyngeal carcinoma. Because this virus is ubiquitous globally, additional factors must be involved to explain the striking global variation: notably genetic and environmental factors.,,,
Implicated genetic factors include race (Chinese, Eskimos and Arabs/Berbers in north Africa) as well as polymorphisms of several genes involved in immune regulation, cell cycle control, and DNA repair.,, These include certain HLA haplotypes (HLA A2-B46, A*0206, B*N5502), enzyme polymorphisms (GSTM1, CYP2E1), and susceptibility loci (4p12-p15) have been implicated.,
Contributory environmental factors are mainly dietary-salt-preserved fish, rancid butter, and rancid sheep fat.
There have been several published studies on this uncommon malignancy in Nigeria but none from our locality; thus, this study is aimed at documenting the pattern of NPC in our hospital.
| Materials and Methods|| |
This was an ethically approved retrospective study of all NPCs diagnosed at the Pathology Department of our hospital over a 10-year period (2005–2014). Ethical approval was obtained from the Institutions Research Ethics Committee.
Relevant biodata (age and gender) were obtained from laboratory records. Histology slides of all cases were retrieved and reviewed by the authors. Missing slides were re-cut from archival paraffin blocks. Cases without complete biodata or missing slides and tissue blocks were excluded from the study. All biopsies had been fixed in 10% formol saline, and then routinely processed for paraffin embedding. Sections were cut at 4 microns and stained with hematoxylin and eosin (H and E). Diagnoses were in accordance with WHO histological classification of tumors.
| Results|| |
Sixty-nine nasopharyngeal malignancies were diagnosed during the 10-year study period, comprising 1.3% of all cancers. Forty-seven were in males and 22 were in females (M: F = 2.1:1). Their ages ranged from 16 to 70 years with median of 38 years [Table 1]. NPC most frequently (81%) occurred in 3rd to 5th decades, with bimodal peaks in the 3rd and 5th decades [Figure 1] of life.
|Table 1: Histological types, age, and sex distribution of nasopharyngeal cancers in Kano (ORIGINAL)|
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The bimodal age peak was mostly owing to squamous carcinoma. Among the histological types, squamous carcinoma comprised 67 cases (97.1%) and adenocarcinoma 2 cases (2.8%), which was by far the most common histologic type comprising 97.1% (67 cases). This was distantly followed by 2 cases (2.8%) of other carcinomas.
Approximately, 80% of the squamous carcinomas were non-keratinizing, while only 20% were keratinizing.
There was one papillary adenocarcinoma and an adenoid cystic carcinoma. With exception of adenocarcinoma, all histologic types were most common among males.
| Discussion|| |
NPC is uncommon, except for the endemic regions, however, it forms an important part of head and neck cancers. NPC accounted for 1.3% of all cancers in our center, which is within the national range-from 1.1% in Lagos to 2% in Ibadan, Ilorin, and Zaria.,,, In Ghana, Kitchner et al. reported a comparable frequency of 1.2%. However, in high incidence South East Asia, relative frequencies of NPC varied from 6.7% in Malaysia to as much as 32% of cancers in Guangzhou, Southern China, where this upper respiratory malignancy was most common cancer.,
High rates are also observed in North Africa and parts of East Africa.,,,, In the western world, NPC is relatively uncommon comprising <1% of cancers.,
Several reasons have been adduced for this marked disparity in the global distribution of NPC, but none is totally satisfactory, particularly as EBV, the major aetiologic factor is ubiquitous worldwide. Genetic factors are probably involved as higher rates are observed among Chinese and their descendants in Malaysia, Thailand, Vietnam, and U.S. than among non-Chinese locals. Several genetic loci including certain HLA haplotypes (HLA A2-B46, A * 0206, B*N5502), enzyme polymorphisms (GSTM1, CYP2E1), and susceptibility loci (4p12-p15) have been implicated.,,
These genetic factors are thought to interact with dietary factors such as salted fish in Southern China, and rancid butter/sheep fat in north Africa to account for the high rates in these endemic areas.,
As in most published studies, males were overwhelmingly preponderant in Kano (M: F = 2.1:1).,,,,, In Jos, Lagos, Maiduguri, Kenya, and Sokoto M: F ratio was 1.6:1, 1.7:1, 2.1:1, 2.2:1, and 2.8:1, respectively.,,,, IARC similarly reports 2-3 fold male preponderance around the world. The reason for this gender disparity is uncertain.
The age range of NPC in our center was quite wide: 16–70 years. Again this is consistent with most Nigerian reports; 14–60 years in Sokoto, 10–81 years in Ibadan, 6–70 years in Maiduguri, and 23–80 years in Ilorin.,,,, However, the mean age in Kano (33.76 years) is lower than other Nigerian studies: 39 years in Maiduguri, 39.1 years in Sokoto, 41 years in Ibadan, 44 years in Lagos, and 48 years in Ilorin.,,,, The reason why our patients present earlier than most studies is not certain, but future studies using larger sample size and involving more centers will probably shed more light in that regard.
As in most low incidence populations, a bimodal age distribution was observed in Kano, with peaks in the third and fifth decades. This is similar to Nwaorgu et al. report in Ibadan, but slightly at variance with reports from Jos and Lagos, as well as other low incidence populations around the world (USA, Malaysia, India), where the first peak was in the 2nd decade.,,,, In North America and Europe, the second peak was a decade or 2 later than in Nigerian studies.
Squamous cell carcinoma was by far the most frequent histologic type comprising 97.1% of NPCs in our center. Similar findings were reported from other parts of Nigeria: 76.7% in Sokoto, 82.6% in Lagos, and 92.5% in Maiduguri.,, Squamous carcinoma also constitutes the overwhelming majority of NPC in other parts of the world, such that NPC is considered squamous unless otherwise stated. Accordingly, WHO classification simply refers to the squamous type as “nasopharyngeal carcinoma.”
Squamous carcinoma subtypes, however, vary around the world. In U.S., keratinizing variant (type 1) is the most frequent. However, in this and other Nigerian studies, as well as high incidence localities such as Southern China and North Africa, the non-keratinizing variant predominates.,,,,
The issue is somewhat complicated by the different WHO classifications used in various studies. In the earlier more widely used 1991 classification, non-keratinizing and undifferentiated are separate categories. However, in the current 2005 WHO classification, both are lumped together as non-keratinizing. Consequently, any study using the current 2005 classification will have much larger proportion of non-keratinizing than those that used 1991 classification.
This sub-classification brouhaha is hardly consequential, given that the histologic subtypes of squamous carcinoma are not considered significant prognostic or predictive factors.
Other non-squamous histological types (adenocarcinoma, sarcomas, and lymphomas) in Kano were few, and their numbers were not statistically significant.
The limitation to our study has to do with missing slides, paraffin tissue blocks, and some cases without complete biodata, however, because those cases were few, we believe the validity of the study was not affected.
In general, our findings are largely consistent with other Nigerian reports and most low incidence regions around the world. There are, however, some notable differences with the western world in terms of relative frequency, histological subtypes, and age distribution.
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Conflicts of interest
There are no conflicts of interest.
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