|Year : 2015 | Volume
| Issue : 1 | Page : 51-54
Skin adnexal tumours in Kano, Northern Nigeria
Raphael Solomon1, Ibrahim Yusuf2, Ochicha Ochicha2
1 Department of Pathology, University and Aminu Kano Teaching Hospital, Kano, Nigeria
2 Department of Bayero University and Aminu Kano Teaching Hospital, Kano, Nigeria
|Date of Web Publication||8-May-2015|
Department of Pathology, Aminu Kano Teaching Hospital, P.M.B 3452, Kano 700001
Source of Support: None, Conflict of Interest: None
Background and Objective: Tumours of skin adnexae are an uncommon group of neoplasms that have not been formally studied in our locality. We undertook this review to document and evaluate the pattern in Kano, northern Nigeria. Materials and Methods: This is a 10-year (2004-13) retrospective study of all skin adnexal tumours diagnosed at the pathology department of Aminu Kano Teaching Hospital (AKTH), Kano. Results: Ninety-two skin adnexal tumours were diagnosed during the study period, and there was no significant gender predilection - males (49%), females (51%). The overwhelming majority were benign (86%), while malignancies comprised just 14%. Patients ranged from 4 to 90 years of age, peaking in the third and fifth decades. The most common histological types were nodular hidradenoma (17.4%), eccrine poroma (9.8%) and pilomatrixoma (9.8%), with sebaceous carcinoma (5.4%) as the most frequent adnexal malignancy. The tumours were most commonly located in the head and neck region (52%), followed by the trunk (25%) and extremities (23%). Conclusion: Skin adnexal tumours are relatively uncommon in Kano affecting predominantly people in the third and fifth decade without a definitive sex predilection. Most of the tumours showed sweat gland differentiation with nodular hidradenoma and sebaceous gland carcinoma being the most common benign and malignant tumours, respectively.
Keywords: Hidradenoma, Kano, pilomatricoma, sebaceous carcinoma, skin adnexa tumours
|How to cite this article:|
Solomon R, Yusuf I, Ochicha O. Skin adnexal tumours in Kano, Northern Nigeria. Niger J Basic Clin Sci 2015;12:51-4
| Introduction|| |
The skin adnexae is a part of the epidermis of the skin composed of different cells grouped as sweat gland (apocrine/eccrine), sebaceous gland and hair follicle but derived from the same origin. , They give rise to a relatively rare but bewildering large and varied group of tumours and tumour variants that differentiate along one or more adnexal lines in the same tumour. ,, The diagnosis of skin adnexal tumours (SATs) presents difficulties to the general practitioner (Pathologist) related not only to the large variety of different tumours and their variant forms, but also the frequency of differentiation along two or more adnexal lines in the same tumours, the various classification schemes, complicated nomenclature and their relative rarity, which makes the Pathologist unable to maintain ready familiarity with them. ,
SATs are often nonspecific, nondescript flesh-coloured solitary or multiple papulo-nodular lesions with varying clinic-pathologic significance according to type and clinical context: Some entirely benign but locally aggressive tumours may be confused clinically with cutaneous cancers such as basal cell carcinoma, while malignant ones like eccrine and apocrine carcinomas are often mistaken histologically for metastatic adenocarcinoma to the skin because of their tendency for abortive gland formation. ,,, Furthermore, other SATs such as trichilemmoma, cylindroma and others exhibit mendelian patterns of inheritance and germline mutations associated with genetic syndromes and internal malignancies. ,, The foregoing stresses the need for the Pathologist to be familiar with and make appropriate diagnosis of SATs so that proper surgical treatment, counselling and follow-up of patients can be instituted.
There has not been any published work on SATs from our centre, which is a major referral centre for histopathological services in north western Nigeria. In fact, the literature on the histopathological pattern of SATs in the African population is almost non-existent with only one published work  available to the Authors. The objective of this study was to document the histopathological spectrum of skin adnexal tumours, their age, sex and anatomical site distribution in the Pathology department of Aminu Kano Teaching Hospital (AKTH) and compare our findings with those from previous series.
| Materials and methods|| |
This was a 10-year retrospective study of all histologically diagnosed skin adnexal tumours at the Pathology department of AKTH, Kano, Nigeria, from 1 st January 2004 to 31 st December, 2013.
All biopsies had been fixed in 10% formal saline, routinely processed for paraffin embedding then microtome sectioned at 5μm and the resulting slides stained with Haematoxylin and Eosin. Special stains such as Periodic acid Schiff (PAS) and Alcian blue were deployed where necessary. Relevant data such as age, sex, anatomical sites and histological diagnosis were obtained from the histology request forms and duplicate copy of the histology reports.
The corresponding histology slides were retrieved, reviewed and the tumours classified based on their adnexae origin into sweat gland, hair follicle and sebaceous gland tumours by the study Pathologists. The results were then analyzed and presented in simple frequency table.
| Results|| |
A total of 92 skin adnexal tumours (SATs) were seen during the 10-year study period. Forty-five (49%) were males while 47 (51%) were females giving a male to female ratio of 1:1. The tumours were commonly located on the head and neck region (52%), followed by the trunk (25%) and extremities (23%).
The overall age range of patients with SATs in this study was 4-90 years with mean age at presentation of 37 years and peak incidence seen in the third and fifth decades. The benign tumours affected patients between 4-90 years with a mean age of 37 years while the malignant tumours affected patients between the ages of 20-70 with a mean age of 40.6 years. [Table 1] shows the relative frequency of different histologic types as well as the age and gender distribution of skin adnexal tumours in Kano (2004-2014).
|Table 1: Relative frequency, age and gender distribution of skin adnexal tumours in Kano |
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The tumours were categorized based on their adnexae origin with 50 (54.4%) sweat gland, 27 (29.3%) hair follicle and 15 (16.3%) sebaceous gland tumours, respectively. There were 79 (86%) benign to 13 (14%) malignant lesions giving a striking benign to malignant ratio of 6.7:1. The benign tumours affected 41 (44.6%) females and 38 (41.3%) males while the malignant tumours affected 6 (6.5%) females and 7 (7.6%) males.
The commonest tumours were all benign: Nodular hidradenoma-16 cases (17.4%), eccrine poroma-9 cases (9.8%), pilomatrixoma-9 cases (9.8%), trichofolliculoma-7 cases (7.6%) and apocrine hidrocystoma-7 cases (7.6%). Sebaceous carcinoma (5.4%) and malignant trichilemmal tumour (2.2%) were the most frequent malignancies.
| Discussion|| |
Ninety-two cases of SATs were seen during the 10-year study period, representing an annual hospital-based frequency of 9.2 cases per year. This number is reasonably small for the only department providing histopathological service in Kano, the largest city in northern Nigeria that is also the capital of the most populous state  in Nigeria and a major referral centre for the neighbouring north western states.
It is, however, in keeping with most of the reviewed literature, which showed similar paltry figures. ,,,,,, Samaila  in Zaria, documented 52 cases over a 16-year period, while Ankit et al.  in South India recorded 56 in a 7-year study. Two 3-year studies in India documented 25  and 33  cases each. A 13-year study in Malaysia  recorded 112 cases, while a 5-year study in Pakistan  reported 166 cases. These small sample sizes underscore the rarity of skin adnexal tumours. ,, It is also quite possible that the true incidence is under-reported as most SATs are benign non-life threatening lesions with minimal clinical morbidity. Consequently, low income patients in resource poor countries like ours may not seek medical attention they can ill-afford. Even when the tumours are surgically excised, many patients in our locality do not bother with the additional expense of histopathological examination.
In Iran where medical care is free and of relatively better quality, Kambiz et al.  reported a whopping 1016 (cases of) SATs over a 5-year period. While no reliable data exist on the impact of race and geography on the incidence of these lesions, the reason for the higher prevalence in Iranians is unclear. It should be noted though that, the work by Kambiz et al.  was carried out at Razi hospital in Tehran, a tertiary care and referral dermatology/dermatopathology unit where biopsies are more frequent and may explain the huge sample size.
The overwhelming majority of adnexal tumours in this study were benign (86%), which is consistent with other published reports. In the studies by Samaila,  Ankit et al.  and Radhika et al.,  benign tumours comprised 88.5%, 80.4% and 77.1%, respectively.
SATs in this series mostly involved the head and neck (52%), distantly followed by the trunk (25%) and extremities (23%). This preponderance of head and neck is in accord with 46-64.5% in other studies, ,,,, and has been ascribed to the abundance of pilosebaceous units, apocrine and eccrine sweat glands in the head and neck region.
The age distribution of patients in this study demonstrated wide range of occurrence (4-90 years), which conforms with reports across the globe. ,,,, Similarly, the mean age of 37 years in this study agrees with 29.8-40.2 years in various published series. ,,, While malignant SATs in this study affected patients between the ages of 20-70 years, they affected only patients older than 50 years in India.  The mean age of 40.6 years for malignant SATs in this series is almost a decade and half earlier than what was noted in Pakistan. 
However, the peak age group of SATs differs substantially among various published reports. Like in this study, Samaila  and Kambiz et al.  both noted a bimodal peak incidence. In this study and in Iran,  SATs peaked in the third and fifth decades. In Zaria,  adnexal tumours peaked in 2 nd and 5 th decades, while in India  they peaked in the sixth decade. There is no clear explanation for the bimodal peak in this and other studies, but the foregoing shows there is no discernible global pattern as to which age group has the highest occurrence. ,, The small sample sizes of several published reports undermine their statistical significance and may help explain the wide disparities in their age distribution.
As with most published reports, there was no significant gender predilection in this study. ,,, A few studies from Malaysia  and India , however document a modest female preponderance with female to male ratios ranging from 1.5:1 to 2.4:1.
Sweat gland tumours were the most common histological type (54%) in this review followed by pilar tumours. This conforms with reports from Zaria,  South India,  Pakistan  and Paraguay,  but at variance with reports from Iran,  Malaysia  and Korea  where pilo-sebaceous tumours were more common.
Hidradenoma was the most frequent sweat gland tumour in this study and has a mean age of 43 years. This was followed by eccrine poroma and pilomatricoma. Nodular hidradenoma was also the commonest adnexal tumour in Zaria, India and Pakistan, while nevus sebaceous of Jadassohn and pilomatricoma were the most prevalent in Iran and Korea, respectively. ,,,, Majority (50%) of the cases of nodular hidradenoma affected the head and neck region distributed in the scalp, face, cheek and neck. The trunk and the lower limb accounted for four cases each.
As in most studies around the globe, malignant SATs were few in this review. Only 13 cases (14%) were documented. Sebaceous carcinoma was by far the most common with 5 cases (38%). Sebaceous gland carcinoma was also the most frequent adnexal malignancy in India, Pakistan, Iran and South Korea. ,,, Samaila in Zaria, however, documented sweat gland carcinoma as the most common skin adnexal malignancy.  Four of the cases of sebaceous carcinoma in this study affected the eyelid while the remaining one was seen in the lower limb. This is understandable as sebaceous glands are abundant in the eyelids independent of hair follicles. 
In conclusion, skin adnexal tumours are relatively uncommon in Kano affecting predominantly people in the third and fifth decade without a definitive sex predilection. Most of the tumours showed sweat gland differentiation with nodular hidradenoma and sebaceous gland carcinoma being the most common benign and malignant tumours respectively. While a general pattern cannot be drawn for Nigeria and Africa given the dearth of available reports, our findings are generally consistent with global pattern in terms of tumour types, relative frequency, age, sex and anatomic distribution.
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