Abstract
Thyroid cancer is the most common endocrine cancer. There are various histopathological types requiring different therapeutic approaches and having variable prognoses. The objective of this study was to determine the pattern of thyroid cancers in Nigeria. The systematically searched databases were African Journal Online, Google Scholar, PubMed, and SCOPUS. The pre-print databases Research Square, SciELO, and medRxiv were also systematically searched. Moreover, the available grey literature was equally searched. The quality of the selected studies was assessed using the Newcastle-Ottawa scale. The meta-analysis was done using Meta XL version 5.3. The DerSimonian Laird random effect model was used for the meta-analysis. The heterogeneity of the selected studies was determined using the I(2) statistic and Cochran's Q test. Publication bias was assessed with the Luis Furuya-Kanamori (LFK) index and Doi plot. Twenty-six studies met the eligibility criteria. The total sample size was 1224. In Nigeria, thyroid cancer was most common in the 4th and 5th decades of life. It was 3.5 (95% CI 3.0-4.6, p < 0.0001) times commoner in females than males. The pooled proportions of thyroid cancers included papillary thyroid cancer, 46% (95% CI 40-53); follicular thyroid cancer, 39% (95% CI 32-45); medullary thyroid cancer, 7% (95% CI 6-9); and anaplastic thyroid cancer, 5% (95% CI 3-7). The trend showed a change from follicular cancer predominance to papillary cancer over the past two decades. Papillary thyroid cancer is the commonest type in Nigeria. Thyroid cancer is seen more in females and it occurs most commonly in middle age.