This 57 years (1961–2018) review of orbito-ocular tumours in Nigeria has shown that the majority (approximately 60%) of orbito-ocular tumours in Nigeria are malignant, with the rest being benign and inflammatory [1, 2, 12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. This finding differs from what was reported in a 10-year review in Chiba, Japan where 57.2% and 35.9% were benign and malignant respectively [33]. The likely reasons for this difference include location, with the index review on the west coast of Africa while the other was in far southeast Asia. Other likely reasons include differences in environmental factors, diet, and genetics. It is also possible that many patients with benign tumours who did not have any visual symptoms could have decided not to present to the hospital in our environment (Table 2).

Retinoblastoma was the most common orbito-ocular tumour from this nationally representative review conducted across all age groups. The finding is similar to an earlier report from Saudi Arabia by Johnson et al. [34] Though that study was conducted among children of paediatric age groups. This, however, is in contrast with reports from authors in Europe (Jensen) and the US (Shields) [35, 36]. Orbital invasion is the main reason for the similarity found in Nigeria (the index review) and the report from Saudi Arabia which is not the case in Europe and America [32, 36, 37]. This is most likely because of late presentation predominantly noticed in the studies included in this review. This is similar to an earlier report by Fasina and Ubah in Ibadan, Nigeria [38]. From Table 5, about 5 of the included studies categorized the tumours by anatomical site of the eye involved which were the eyeball (intraocular), conjunctiva, orbit, eyelid, optic nerve, and lacrimal gland. Four out of five of these studies (80%) reported intraocular involvement in almost half of the patients (46.8 – 77.0%) had intraocular disease. This classification also supports the high frequency of retinoblastoma, which is the most common primary intraocular tumour (Table 2).

Conjunctival squamous cell carcinoma is the second common tumour in this review. This is similar to reports from other parts of Africa and the tropical world [5, 16, 39, 40]. This high frequency may be attributed to high exposure to sunlight in the tropics as opined by Shield and Shield [41]. Conjunctival squamous cell carcinoma was the most common among the adults in this review. HIV infection is an important comorbidity in patients with conjunctival squamous cell carcinoma. Burkitt’s Lymphoma (BL) was the next in this review. The study by Olurin and Williams [12] (included in his review) reported BL to be the second most frequent tumour, similar to reports from the Western world by Jensen et al [35], Shields et al [36] Mago and Mulla [42] (Table 2).

Next in the log is Rhabdomyosarcoma, which is considered the most common primary orbital tumour in children as highlighted in this review and a few other studies within and outside Nigeria [35, 42, 43]. Another important malignant tumour is basal cell carcinoma, which is the most common malignant lid tumour. There was a relatively low prevalence of 1.5%—4.0% in this review. Previous studies among the Caucasian population have reported a relatively higher prevalence of basal cell carcinoma compared to dark-pigmented races [37, 44]. The likely adducible reason for this is the heavy pigmentation considered to be protective for basal cell carcinoma among ‘blacks’ [1]. Also from the review, the prevalence of melanomas ranged from 2.6 – 9.1%. This is at variance with a previous 20-year retrospective review in Ibadan which reported a 0% prevalence of melanomas [1]. The study in question was a single-centre study which considered 215 tumours, unlike the index review, which considered 2643 tumours over 57 years. The importance of this point is that melanomas may not be as rare as was reported by Fasina et al. in Ibadan. [1]

Benign tumors account for less than 40% of lesions reported in this review. This is unlike what was reported earlier in Chiba Japan in 2021 where almost 60% of lesions were benign.33 The most common lesions were squamous cell papillomas (5.0 – 16.9%), haemangiomas (2.9 – 18.8%), and neavus (2.0 – 10%) unlike cysts (7.8%), neavus (5.9%) and papilloma (6.0%) in Chiba, Japan. The reason for this difference, especially the papilloma, could not be ascertained.

The age range of the patients included in this review was not comprehensively captured in the included studies, probably because of the retrospective nature of all but one of the included studies. (Table 1) However, three studies representing 6.4% of the total sample size were completed among children. (References from Table 1) The higher frequency of childhood tumours such as retinoblastoma, rhabdomyosarcoma, and Burkitt’s lymphoma suggest a higher frequency of children in the studies included in this review. This also may explain why retinoblastoma which is arguably the most common childhood intraocular tumor with a peak age at 18 months, is the most common tumour reported in this review.

The presentation varied and overlapped among the included studies. Proptosis was the main common single presentation in this review. The frequency ranged from 19.0 – 84.6%. This is most likely because orbital space-occupying lesions result in forward protrusion of orbital contents [36]. About 3.1 – 71.2% presented with blindness. This is most likely because of due to a late presentation. This explains why the mean duration of symptoms before presentation is about 10 months in Ibadan [38]. Another presentation that suggests late presentation is orbital involvement and fungating mass which was seen in 4.1 – 56.1% of all presentations. This is a poor prognostic factor for malignant lesions as it implies metastasis to distant sites at presentation. Another common presentation was leukocoria (20.4 – 61.5%). This is not surprising as it is the most common presentation of retinoblastoma [1], which was also noted to be the most common orbito-ocular tumour in this review.

Usually, the outcome is expressed in terms of recurrence after standard treatment or survival rate. Very few of the included studies considered treatment modalities and outcomes of the condition. This varied mainly according to the orbito-ocular lesion under consideration. Five of the studies included in this review attempted to discuss the treatment or outcome of the tumours (see Table 5).

The series by Owoeye et al [15] (2005) reported that enucleation and exenteration were offered to the patients in the proportion of 73.9% and 26.1% respectively. Almost half (45.5%) were lost to follow-up (maybe presumed dead) while the rest died on admission. Exenteration and enucleation were the most common interventions at different proportions in the included studies. Others included excision biopsy, adjuvant chemotherapy, and radiotherapy. Abdu and Malami in 2011 [20], reported that almost half of the 13 patients who needed chemotherapy had the recommended full six cycles for retinoblastoma. Another series by Alabi et al [23] reported 87.9% cases of loss to follow-up and a high probability of unreported mortality among these.

From this review, it is evident that orbito-ocular tumours are a group of morbidity and mortality-laden pathologies. There is a significant risk of recurrence, even with the best treatments. Several factors contribute to some of these undesirable outcomes. Late presentation, which may be because of poor awareness or poor health-seeking habits and lack of access to the correct information and care. Access to quality healthcare is a multipronged challenge in developing countries like Nigeria, which no universal health coverage. Thankfully, the recent restructuring of the health insurance administration in the country has led to the inclusion of cancer chemotherapeutic agents to the list of medications covered by the National Health Insurance Agency (NHIA) [45]. Out-of-pocket-payment is another main challenge faced by Nigerians because of the lack of Universal Health Coverage, especially with the rising rate of inflation in the country. Even with some funding, some chemotherapeutic agents are not readily available. It is also noteworthy that the mere inclusion of anti-cancer medications to the NHIA list does not solve the problem of poor access, as current statistics still show that less than 5% of Nigerians are enrolled into the national health insurance system [46]. Another study in a tertiary eye clinic found that unemployed people and unskilled workers who had no form of insurance coverage spent more than their average monthly income on medications compared to insured patients, most of whom are employed professionals or skilled self-employed people [47]. This definitely will adversely affect treatment compliance and adherence.

So far Nigeria has an improved number of ocular oncology experts evidenced by training for new fellows whose numbers could not be estimated from this review [48,49,50], they are however not equitably distributed for different reasons. the improved numbers is expected to translate into more retinoblastoma survivors which is likely due to improved care in the country. This gain also has its challenges as it is expected that when these survivors (who already have some RB mutation) eventually become parents, some of the offspring may have a similar mutation thus increasing the burden of retinoblastoma in the future.

It is also important to note that the outcome, which includes survival rate and recurrence rate, depends on the time of presentation, stage of disease, and pathology under consideration (Table 7). This was highlighted by Uche et al [2] in Enugu and in agreement with results of a recent study in Calabar, Nigeria which considered the patient-related outcome of retinoblastoma in a tertiary hospital showed that 13.2% completed treatment while 26.4% and 22.6% respectively abandoned alone and chemotherapy with surgery [51]. The study showed an association between early presentation (p = 0.005), non-relapse (p < 0.001), and survival rates. Patients with bilateral disease were more likely to die (p = 0.002) and advanced stages and wasting were more likely to die in the study (p = 0.01). Local therapy, besides chemotherapy, was associated with an improved survival rate (p = 0.001) compared to those who had chemotherapy only. Furthermore, external beam radiation, which was mentioned in one of the included articles is another important treatment modality which has reported in studies to have good results where it is available [2, 52,53,54], the infrastructure for this intervention is not readily available in Nigeria. A recent survey of the state of public funded radiation services in the country reported a crisis state for radiation services in the country with only two (33.3%) out of six of the public regional centres actively treating patients [55].

Except for one prospective study included in this review, all the others were retrospective studies and the data collection methods were not uniform. This affected the quality of data obtained from this review as typified by some scanty cells in the tables above. Despite these limitations, this systematic review provided a good picture of the patterns of orbito-ocular tumours in Nigeria. Authors recommend that the body of ocular oncologists and plastic surgeons develop a protocol similar to that used in the report by Fasina in 2011 [1].