|Year : 2015 | Volume
| Issue : 1 | Page : 55-60
Histopathological pattern of thyroid lesions in Kano, Nigeria: A 10-year retrospective review (2002-2011)
Raphael Solomon1, Yawale Iliyasu2, AZ Mohammed1
1 Department of Pathology, Aminu Kano Teaching Hospital, Kano, Nigeria
2 Department of Pathology, Ahmadu Bello University Teaching Hospital, Shika Zaria, Nigeria
|Date of Web Publication||8-May-2015|
Department of Pathology, Aminu Kano Teaching Hospital, Kano
Source of Support: None, Conflict of Interest: None
Background and Objective: Thyroid gland lesions occur globally with geographical variation in incidence and histopathological pattern related to age, sex, dietary and environmental factors. There is, however, no published histological study from northwestern Nigeria; hence, we undertook this study to describe the spectrum, frequency, age and sex distribution of thyroid gland lesions seen in Kano, as well as compare the findings with previous studies done in Nigeria and elsewhere. Materials and Methods: This is a retrospective descriptive study of all thyroidectomy specimens received from January 1 st , 2002 to December 31 st , 2011 at the histopathology department of Aminu Kano Teaching Hospital, Kano, Nigeria. Results: Five hundred and twenty-two thyroid gland lesions were diagnosed during the ten year period with a female to male ratio of 6.4:1. The ages range from 5 months to 86 years with a mean age at presentation of 36.3 years and relative peak age of incidence occurring in the 30-39 years group. The most common entity was goitre (57.2%) with a mean age at presentation of 37.5 years. It was followed by thyroid adenomas (15.7%) and thyroid carcinomas (12.6%). Specifically among cancers, papillary carcinoma predominated (53%), followed by follicular carcinoma (33.3%) and medullary carcinoma (9.1%). There were 36 cases (6.9%) of thyroglossal duct cysts and 28 cases (5.4%) of toxic hyperplasia while thyroiditis was uncommon with only 2 cases (0.4%). Conclusion: This study shows that thyroid gland diseases are common in Kano and are seen in both genders with a striking female preponderance. It revealed a higher incidence of papillary carcinoma over follicular carcinoma, a reverse of the finding of an earlier clinicopathological study on thyroid gland diseases in Kano. The age and sex incidences as well as the histological featuresof thyroid lesions in this study are, however, similar to reports from other local and international studies.
Keywords: Adenoma, carcinoma, goitre, histopathology, Kano, thyroid lesions
|How to cite this article:|
Solomon R, Iliyasu Y, Mohammed A Z. Histopathological pattern of thyroid lesions in Kano, Nigeria: A 10-year retrospective review (2002-2011)
. Niger J Basic Clin Sci 2015;12:55-60
|How to cite this URL:|
Solomon R, Iliyasu Y, Mohammed A Z. Histopathological pattern of thyroid lesions in Kano, Nigeria: A 10-year retrospective review (2002-2011)
. Niger J Basic Clin Sci [serial online] 2015 [cited 2020 Jan 27];12:55-60. Available from: http://www.njbcs.net/text.asp?2015/12/1/55/150474
| Introduction|| |
The thyroid gland produces hormones that control oxygen consumption, the metabolism of macromolecules, the basal metabolic rate of most body cells and are necessary for normal growth and maturation as well as proper development of the central and peripheral nervous system. ,, Consequently, pathologic lesions of the thyroid gland are of importance not only because they affect the functions of other organs but also since most are amenable to highly effective surgical or medical treatment. They range from congenital lesions, goitre (hyperplastic/metabolic), inflammatory to neoplastic lesions. These diseases present clinically either as conditions associated with hyperthyroidism/hypothyroidism or as mass lesions.  Surgical excision and histopathological evaluation are crucial to establish diagnosis in the latter scenario. Thyroid diseases were thought to be uncommon in Africans in the early 1960s and 1970s, and gross underreporting is blamed for this scenario.  It is now known that diseases of the thyroid gland are the second most common endocrine disorders seen in endocrinology clinics in Nigeria, while thyroid surgery constitute a significant proportion of surgical practice in Nigeria. ,,]
There are only few histopathological reports on the general pattern of thyroid diseases from various parts of Nigeria.  These studies are predominantly from the southern parts of the country and given the differences in demography, lifestyle and possibly genetics, they may not be representative of the pattern in northern Nigeria. Furthermore, given the increased availability of iodised salt, flour and food supplements in Nigeria due to government adoption of the universal salt iodination strategy for reduction of iodine deficiency disorders promoted by ICCIDD/WHO/UNICEF and the new information in international literature of change in the pattern of thyroid lesions as communities transit from iodine deficiency to iodine sufficiency status, there is need to document the histopathological pattern of thyroid lesions in northern Nigeria. 
The aim of the study was to present the histopathological pattern of thyroid gland lesions as seen in the histopathology department of Aminu Kano Teaching Hospital (AKTH), Kano. AKTH is a referral centre for most hospitals in Kano and the neighbouring Katsina, Jigawa, Bauchi and Kaduna states.
| Materials and methods|| |
The materials for this study consisted of the slides and paraffin-embedded blocks of all the thyroidectomy specimens received in the histopathology department of AKTH over a 10-year period from January 1 st , 2002 to December 31 st , 2011.
For each case, the laboratory request form and duplicate copy of the histological report were retrieved and relevant clinical information such as age, sex and the histological type of thyroid disease were extracted. All biopsies had been fixed in 10% formal saline, routinely processed for paraffin embedding then microtome sectioned at 5μm and stained with Haematoxylin and Eosin. The corresponding slides were retrieved from the archive and reviewed by the study pathologists. The lesions were classified based on their main histological diagnostic features into: Congenital, goitre (colloid/nodular), inflammatory and neoplastic lesions. The neoplastic lesions were then classified according to the WHO histological classification of thyroid tumours.  The data was subsequently analysed and presented as simple frequency tables and percentages with photomicrographs of some representative lesions taken.
| Results|| |
A total of 522 thyroid specimens were received over the 10-year period, representing 1.5% of all the cases seen at the histopathology department. There were 451 females (86.4%) and 71 males (13.6%) giving a female to male ratio of 6.4:1 [Table 1]. The overall age range was from 5 months to 86 years with a mean age at presentation of 36.3 years and relative peak age of incidence seen in the 30-39 years age group (33.3%).
|Table 1: Age and sex distribution of patients with neoplastic thyroid lesions in Kano |
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|Figure 1: Multinodular goitre showing variable-sized, colloid-rich follicles lined by flattened inactive epithelium. (H and E, ×20)|
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Goitre [Figure 1] is the most common pathologic entity, constituting 57.2% of all the cases studied and having a female to male ratio of 11.5:1 and a mean age of 37.5 years. About 90% of these were multinodular goitre while simple colloid goitre accounted for the remaining.
Toxic hyperplasia of the thyroid represented 5.4% of all the cases seen, with age range of between 18 and 80 years and a mean age at presentation of 37.1 years. All the cases except a 24-year-old man with Graves's disease were females. Inflammatory thyroid lesions accounted for only 2 (0.4%) cases seen in this study. They were seen exclusively in females comprising of one case each of Hashimoto thyroiditis and sub-acute lymphocytic thyroiditis.
Thyroglossal duct cysts were the only congenital thyroid gland anomaly seen in this study and accounted for 6.9%. There is a slight male preponderance. The age range of thyroglossal duct cyst was from 5 months to 58 years with an average age of 17 years. The majority of the cases occurred in the first two decades of life and no case was seen after the sixth decade.
The neoplastic thyroid lesions accounted for 157 cases (30.1%) of all the cases studied [Table 2]. They affected the age range of 15 to 80 years with a mean age of 35.8 years. There were 130 females and 27 males with female to male ratio of 4.8:1. The benign thyroid neoplasms consisted mainly of adenomas accounting for 82 (52.2%) of all the neoplastic lesions. Others included 4 cases (2.5%) of mature cystic teratoma and one case (0.6%) each of leiomyoma, neurofibroma, dermoid cyst, cystic lymphangioma and hamartoma, respectively.
|Figure 2: Papillary carcinoma showing top: Malignant cells arranged in papillary pattern around a fibrovascular connective tissue and below: cells with characteristic "Orphan Annie eye nuclei" (H and E, ×20)|
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Malignant thyroid lesions accounted for 66 cases (42%) of all the cases of thyroid neoplasms reviewed. They were exclusively carcinomas and affected a wide age range from 17 to 80 years with a mean age of 40 years. The peak age range was in the 4 th and 5 th decades of life accounting for 30 (15 each) cases with female to male ratio of 3.7:1. The most common histopathological variety of thyroid carcinomas was papillary carcinoma (53%) followed by follicular carcinoma (33.3%). Six cases (9.1%) of medullary carcinoma were encountered in this study while there was one case each (1.52%) of anaplastic carcinoma, squamous cell carcinoma and secondary/metastatic squamous cell carcinoma.
Papillary carcinoma was seen in the age range of 17 to 70 years with a mean age at presentation of 38.1 years while follicular carcinoma was seen in the age range of 17 to 80 years with a mean age of 42.9 years.
| Discussion|| |
Thyroid gland lesions are common and occur worldwide. ,, Thyroidectomy specimens constituted 1.5% of the surgical pathology load in the histopathology department of AKTH during the study period. This is comparable to the 0.9-2.2% reported in some Nigerian series and the 2-3.6% reported in International series. ,,,, The incidence and histopathological pattern of thyroid diseases show geographical and regional variations related to age, sex, dietary and environmental factors. 
The mean age of patients with thyroid diseases in this study was 36.3 years and the peak incidence (33.3%) seen in the age group of 30-39 years. These results are consistent with findings from an earlier study in this centre, which reported a median age of 36.5 years and peak age prevalence between 30 and 39 years.  A report from Lagos found that the majority of goitres occurred in the age group of 30-39 years while in Port-Harcourt, the highest frequency of cases was seen between 31 and 40 years of age. ,
Thyroid diseases essentially affect women with a remarkable female preponderance reported for all thyroid lesions except thyroglossal duct cyst which shows no sex predilection. ,,,,,,,,,,,,
The female to male ratio found in this study was 6.4:1, which compares favourably with 7:1, 6.2:1, 6:1 and 5.7:1 from Lagos, Enugu, Ile-Ife and Ilorin, respectively. ,,, Hill et al. (2004) in Kenya reported a female to male ratio of 7.2:1 while Tsegaye et al. (2003) in Ethiopia recorded a ratio of 4.5:1. , This ratio is also similar to reports from the United States of America, SaudiArabia and Pakistan, which recorded female to male ratios of 7:1, 6.2:1 and 4.5:1, respectively. ,,
A significant number of the cases in this study were non-neoplastic thyroid lesions constituting 69.9% of the cases. This is comparable with reports from some Nigerian studies but lower than reports from others. ,,,, This observed preponderance of non-neoplastic lesions is in consonance with findings from the Kenya (60.5%) and USA (84.1%). ,
Goitre is the most predominant thyroid pathology in this study. It occurred in 79.6% of females similar to the series reported from Lagos (79%), Ile-Ife (68.6%) and Ilorin (65.1%). ,, Majority of the women are in the active reproductive age group of 20-40 years which agrees with the findings in Lagos.  This high prevalence of goitre in women is believed to be due to the physiological demands of puberty, menstruation, pregnancy and lactation.  Overall, goitres accounted for 57.2% of all the thyroid lesions and 81.9% of the non-neoplastic thyroid cases seen. This frequency of 57.2% for goitres in this study is similar to the frequency recorded in earlier work in Kano (68%), Enugu (63.2%) and Port-Harcourt (52.5%). ,, It is, however, lower than the 73.4-74.8% recorded in other Nigerian series and the 73-76.9% documented in some African studies. ,,,,
The explanation for the reduced incidence of goitres in this study compared to other studies is unclear but it may be related to increased commercially available iodised salts, flour and other food supplements to the populace due to the collaborative efforts of the Federal government and the National agency for food and drug administration and control in the last two decades.  The goitres consisted of multinodular goitre (53.6%), simple/colloid goitre (3.4%) and one case (0.19%) of amyloid goitre. Multinodular goitre was the most common type of non-toxic goitre similar to the findings in some published works. ,,,,,,
Enlarged thyroid gland with excessive circulating thyroid hormones (hyperthyroidism) leading to a hypermetabolic state or thyrotoxicosis is called toxic hyperplasia of the thyroid gland.  The common causes are Graves's disease, hyperfunctional multinodular goitre and hyperfunctional thyroid adenoma. While Graves's disease has an autoimmune basis, the latter two have no such basis. In this work, toxic hyperplasia consisted of Graves's disease and toxic goitre and they accounted for 5.4% of all the cases in this study. This finding agrees with the 1.8-5% documented in some local studies and the 7.7-8% reported in the Middle East but low when compared to the 20-50% recorded for Europe and America. ,,,,,, While this may lend credence to the observation that thyrotoxicosis is relatively uncommon in Africans, it should be noted that most patients with toxic goitres are treated medically and only few cases are incidental cases operated on. 
Only 2 cases (0.4%) of thyroiditis were seen in this study. They were seen exclusively in females comprising of one case each of Hashimoto thyroiditis and sub-acute lymphocytic thyroiditis seen in a 24 year and 31 year old female respectively. The rarity of inflammatory thyroid diseases is supported by findings from other reports in Nigeria where they constituted 0.9%-3.8% of cases studied. ,,,, The figures are however relatively higher in the Middle East. ,
Although rare, thyroglossal duct cysts are the most common clinically significant congenital thyroid lesion and the most common congenital cause of anterior neck swellings in children. , They accounted for 6.9% of all the thyroid specimens in this study with 36 cases, similar to the 1.8-6.9% recorded in some local and International studies. ,,,,,, The relative rarity of congenital thyroid lesions is supported by their paucity in previous studies from Africa, the Middle East and the USA. ,,,, The congenital thyroid lesions are said to have neither sex predilection nor hereditary predisposition. , This study, however, recorded a slight male preponderance with 19 of the 36 cases seen in males. Although these cysts are said to bear some risk of infection and malignant transformation of the thyroid tissue within them, no such observation was made in this study. ,
Thyroid adenoma accounted for 15.7% of all the cases reviewed and constituted 89% of the benign neoplasms. The preponderance of adenoma over the other benign thyroid tumours in this study compares with studies globally. ,,,,,,, This figure of 15.7% concurs with the 10-21% recorded for adenoma from Nigeria, Africa and the USA. ,,,, Some series in Nigeria documented lower frequencies of adenoma. , This variation has been attributed to differences in the relative frequencies of simple goitre in such areas.  Follicular adenoma represented the most common histological subtype similar to what is recorded in literature. There were four cases (4.9%) of mature teratomas seen in this study similar to the report of two cases of mature teratoma by Saad et al. (2007) in Zaria. One case each of Neurofibroma and lymphangioma were recorded in this work as was also documented by Nzegwu et al. (2010) in Enugu. ,
Thyroid cancer was diagnosed in 12.6% of all the thyroid specimens received in this study. This was similar to the 10.9-14.1% in some Nigerian series but higher than the 8.1% and 7% reported by Adeniji et al. (1998) and Abdulkareem et al. (2005) in Ilorin and Lagos respectively. ,,,,, There is no clear explanation for the lower incidence of thyroid cancer in Ilorin and Lagos.
The predominant histological type of thyroid carcinoma in this study was papillary carcinoma [Figure 2] similar to other Nigerian series and in keeping with reports from some International series. ,,,,,, This finding is however at variance with some local reportswhich found follicular carcinoma to be the most common thyroid cancer. ,,, Papillary carcinoma represented 6.7% of all the thyroid specimens and 53% of the malignant thyroid tumours. This figure of 53% agrees with reports by Saad et al. in Zaria (70.5%), Nzegwe et al. in Enugu (56.5%) and Seleye-Fubara et al. (2009) in Port-Harcourt (54.5%). ,, Papillary carcinoma of the thyroid is the most common type globally and in iodine sufficient areas while follicular carcinoma have higher frequency in iodine deficient areas. ,, Kano in northwestern Nigeria and its catchment areas are in the iodine deficient zone of Nigeria.  However, the impact of the salt and flour iodination programme introduced in Nigeria about two decades ago may account for this changing pattern. ,
Follicular carcinoma was the second most common thyroid cancer with 22 cases (33.3%) and a mean age of 42.9 years. This is similar to the 42 years reported by Nzegwu et al. in Enugu. 
Medullary carcinomas are relatively uncommon with only 6 cases (1.15%). This relative rarity agrees with findings from Lagos (4 cases), Zaria (3 cases), Enugu (1 case), Ile-Ife (1 case) and Port-Harcourt (1 case) in Nigeria as well as reports from Pakistan  (4 cases) and Ethiopia (1 case). ,,,,,,
The study recorded only one case of anaplastic carcinoma similar to the reports of Nzegwu et al., Ngadda et al. (2008), Abdulkareem et al. and Seleye-Fubara et al. in Enugu, Ile-Ife, Lagos and Port-Harcourt respectively. ,,, One case of metastatic squamous carcinoma was also noted consistent with the finding in the Enugu series. 
In conclusion, this study shows that thyroid gland diseases are common in Kano and are seen in both genders with a striking female preponderance. It revealed a higher incidence of papillary carcinoma over follicular carcinoma, a reverse of the finding of an earlier clinicopathological study on thyroid gland diseases in Kano. The age and sex incidences as well as the histological features of thyroid lesions are, however, similar to reports from other local and international studies.
| Recommendation|| |
The information in this study should be considered a baseline data of thyroid diseases in Kano but we recommend that a more elaborate epidemiological, population based prospective multicentre study be carried out to project the exact national profile of thyroid diseases. Such a study will help in outlining plans for early detection, diagnosis and management of thyroid diseases especially the malignant subtypes with a view to reducing the morbidity and mortality associated with them.
This study shows that multinodular goitre (although reduced in incidence relative to an earlier study in Kano), which is largely a preventable disease is the most common thyroid disease in Kano. We thus recommend that iodinisation of salt/flours programme should be sustained by government and non-governmental organisation with accompanying public health education on the need to consume them as a mean of further reducing the incidence of this disease.
This study also revealed that thyroid tumours in general represent the second commonest histologic disease while thyroid carcinoma specifically constitutes the third commonest pathologic entity. We recommend therefore that clinical evaluation of any enlarged thyroid should be thorough and not be overshadowed by the prevalent nodular goitre. Instead, it should always raise the possibility of a thyroid tumour particularly thyroid carcinomas and as a result, efforts should be made to arrive at a definite diagnosis.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]