A pathologic review of ophthalmic tumors in Kano, Northern Nigeria

Ali Bala Umar; Ochicha Ochicha; Yawale Iliyasu

doi:10.4103/0331-8540.102109

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ORIGINAL ARTICLE

Year : 2012 | Volume : 9 | Issue : 1 | Page : 23-26

A pathologic review of ophthalmic tumors in Kano, Northern Nigeria

Ali Bala Umar¹, Ochicha Ochicha¹, Yawale Iliyasu²
¹ Department of Pathology, Bayero University, Kano, Nigeria
² Department of Pathology, Ahmadu Bello University, Zaria, Nigeria

Date of Web Publication

10-Oct-2012

Correspondence Address:
Ali Bala Umar
Department of Pathology, Aminu Kano Teaching Hospital, PMB 3452 Kano
Nigeria

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/0331-8540.102109

Abstract

Background and Objective: Tumors of eye and ocular adnexa are reported to be common in Africa, but no formal study has been conducted here in Kano, the largest Northern Nigerian city. This study is a documentation of the pattern of ophthalmic tumors in our locality. Materials and Methods: This was a 12-year (1999-2010 inclusive) retrospective study of all orbito-ocular neoplasms diagnosed at the pathology department of a teaching hospital. Results : 438 ophthalmic tumors were diagnosed during the study period, of which 79.7% were malignant and 20.3% benign. Males were slightly more preponderant with M/F ratio of 1.3:1. Retinoblastoma and conjunctival squamous carcinoma were the commonest tumors respectively comprising 44.5% and 18.9%. These two ocular malignancies also largely accounted for the bimodal age distribution peaks of ophthalmic cancer in the 1 ^st and 4 ^th decades. Conjunctival squamous papilloma and hemangioma were the most prevalent benign ophthalmic tumors. Conclusion : Our findings were broadly similar to most other Nigerian and African studies but significantly at variance with those of the western world.

Keywords: Conjunctival carcinoma, eye tumors, Nigeria, retinoblastoma

How to cite this article:
Umar AB, Ochicha O, Iliyasu Y. A pathologic review of ophthalmic tumors in Kano, Northern Nigeria. Niger J Basic Clin Sci 2012;9:23-6

How to cite this URL:
Umar AB, Ochicha O, Iliyasu Y. A pathologic review of ophthalmic tumors in Kano, Northern Nigeria. Niger J Basic Clin Sci [serial online] 2012 [cited 2023 May 29];9:23-6. Available from: https://www.njbcs.net/text.asp?2012/9/1/23/102109

Introduction

Tumors of the eye and ocular adnexa have been reported to be more common in Africa than other parts of the world, ^[1],[2],[3] making ophthalmic neoplasms a major cause of clinical morbidity and mortality on the continent.

Histogenetically, these tumors are quite varied owing to the diversity and complexity of tissues within the eye and orbit. Accordingly, their biologic behavior also varies, ranging from benign to pre-malignant and malignant.

In general, benign tumors are more prevalent, although this is less apparent in published studies from sub-Saharan Africa ^{[2],[3],[4],[5],[6]} where comprehensive health care coverage is lacking and many poor patients with non-life threatening benign lesions don't bother with the medical attention they can ill-afford.

Striking epidemiological differences in the distribution of these ophthalmic tumors have been documented around the world. Ocular melanomas, for instance, are the most frequent ophthalmic malignancy among Caucasians in the Western world but are rare in Black Africa. ^{[2],[3],[4],[5],[6],[7],[8],[9]} Conversely, retinoblastoma is much more prevalent in Africa than in high-income developed world. ^{[2],[3],[4],[5],[6],[7],[8],[9]}

Race, genetics, and other poorly-defined environmental factors probably explain some of these observed global disparities.

Although several reports on orbito-ocular tumors have been published in Nigeria, this will be the first documentation of these tumors in Kano, North Western Nigeria. We, therefore, undertook this study to document the pattern in our locality.

Materials and Methods

This is a 12-year (1999 - 2010) retrospective study of all histologically diagnosed orbito-ocular tumors at the pathology department of Aminu Kano Teaching Hospital (AKTH). AKTH is the major tertiary health institution offering histopathology services to the entire Kano state as well as to the neighboring states of Jigawa, Katsina, and Bauchi.

Histology sections were made from formalin-fixed, paraffin-embedded biopsies and then routinely stained with hematoxylin and eosin (H and E). Special stains such as Gordon and Sweet's silver and Mallory's phosphotungstic acid hematoxylin (PTAH) as well as immunohistochemistry for CD20, S100, and Desmin were utilized where necessary.

Biodata comprising age, sex, and site of tumor on all cases were obtained from laboratory records, and the tumors were classified in accordance with the WHO International Classification of Tumors of the Eye and its Adnexa. ^[10]

Results

A total of 438 ophthalmic tumors were diagnosed in our laboratory during the 12-year study period. Eighty-nine (20.3%) were benign and 349 (79.7%) malignant. There was a slight male preponderance with 250 cases (57.1%), while females comprised the remaining 188 cases (42.9%) with a M/F ratio of 1.3:1. Tumors of the eye (conjunctiva and retina) were much more frequent (82.6%) than those of the ocular adnexa, which comprised the remaining 17.4%.

[Table 1] shows the relative frequencies of the different orbito-ocular tumors. Conjunctival squamous papillomas and hemangiomas were the commonest benign tumors constituting 6.6% and 5.0% of ophthalmic tumors, respectively. Other benign neoplasms in this series were conjunctival naevi, lacrimal pleomorphic adenoma, neurofibroma, meningioma, sebaceous epithelioma, optic nerve glioma and one case each of lymphangioma, trichofolliculoma, and apocrine hydrocystoma.

Table 1: Relative frequency of ophthalmic tumors in Kano

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Retinoblastoma (44.5%) and conjunctival squamous carcinoma (18.9%) were the most prevalent ophthalmic malignancies in this study. Most of the retinoblastomas were poorly differentiated tumors lacking Flexner-Wintersteiner rosettes.

Other orbito-ocular malignancies in this series were rhabdomyosarcoma, non-Hodgkin lymphoma, conjunctival melanoma, sebaceous carcinoma, adenoid cystic carcinoma, basal cell carcinoma, mucoepidermoid carcinoma, and Kaposi's sarcoma.

[Table 2] shows the age distribution in years of malignant orbito-ocular tumors. A bimodal peak is evident in first and fourth decades. The much higher first peak is mostly due to early childhood retinoblastoma (0-5 years), while the broader second peak (3 ^rd to 5 ^th decades) is mostly due to conjunctival squamous carcinoma.

Table 2: Age distribution (in years) of ophthalmic malignancies in Kano

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The age range for the benign tumors was 7 months to 97 years with a mean age of 30 years [Table 3].

Table 3: Age distribution (in years) of benign ophthalmic tumors

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Discussion

Malignant tumors were overwhelmingly preponderant in this series, comprising over three-quarters (79.7%) of orbito-ocular neoplasms. This is consistent with reports from other parts of the country as well as sub-Saharan Africa but at variance with reports from the Western world and other high-income countries. ^{[4],[5],[11],[12],[13],[14],[15],[16]} The higher proportion of malignancies in our review may be due to under-reporting of benign tumors as many indigent patients with non-life threatening low morbidity benign lesions do not seek medical attention.

In addition to the ophthalmology department of our hospital, specimens from the ECWA eye hospital also contribute to the relatively high proportion of malignancies in this review.

Retinoblastomas were the most frequent ocular malignancy comprising 44.5% of all orbito-ocular tumors. High rates of retinoblastomas have also been documented in several sub-Saharan African studies, ^{[4],[5],[6],[11],[12],[13],[14]} but race is unlikely to explain this higher prevalence as there is no significant difference between Blacks and Whites in the United States. ^[17] Rather, the high rate of retinoblastoma, which has also been reported in some other parts of the developing world, ^[18],[19] has been ascribed to a yet to be defined infectious agent. ^[20]

As with most other malignant embryonal tumors, retinoblastomas mostly occurred in early childhood (0-5 years). Histologically, most (two-thirds) of our retinoblastomas were poorly differentiated and lacking in Flexner-Wintersteiner rosettes. This is due to late presentation as poorly differentiated tumors are said to be more common with advanced lesions, ^[21] and many of our poor patients only come to hospital after they have exhausted seemingly cheaper alternatives such as patent medicine stores and unorthodox means.

Conjunctival squamous carcinoma was the second most frequent ophthalmic tumor in this study, accounting for nearly one-fifth (18.9%) of orbito-ocular neoplasms. This HPV-associated malignancy, which mostly occurred in sexually active 20-50 year age group, has been linked to HIV. ^[22],[23] Not surprisingly, the rising incidence of conjunctival squamous carcinoma in some parts of Africa has been ascribed to high rates of HIV infection. ^[23],[24] However, this histopathology study did not evaluate the HIV status of conjunctival carcinoma patients as many of them were not screened for HIV sero-positivity.

Embryonal rhabdomyosarcoma and non-Hodgkin lymphomas were the most frequent orbital tumors comprising 2.3% and 2.1%, respectively, of ophthalmic tumors. Higher proportions of these tumors were recorded in Ibadan, Lagos, and Benin. ^{[11],[25],[26]} Unlike in most other African series, ^{[2],[4],[5],[6],[12],[14]} most orbital non-Hodgkin lymphomas were non-Burkitts rather they were intermediate and high grade lymphomas.

The only melanomas documented in this study were 5 conjunctival lesions.

We recorded no metastatic tumors in this study, similar to other Nigerian studies. This is contrary to reports from the United States where metastatic tumors were the second commonest ocular malignancy, with the breast and lungs as commonest primaries. ^[7]

Metastatic tumors are most likely to be detected during long-term management and follow-up of cancer patients.

Conjunctival squamous papillomas and orbital hemangiomas were the commonest benign ophthalmic tumors constituting 6.6% and 5.0%, respectively. This is consistent with reports from most other parts of Africa. ^{[2],[12],[25]}

Conclusion

Malignant tumors constitute about 80% of all ophthalmic tumors seen in Aminu Kano Teaching Hospital, and the majority of these are retinoblastomas, which are seen in the first decade of life. This is similar to findings from other Nigerian studies.

References

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Tables

[Table 1], [Table 2], [Table 3]

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