|Year : 2021 | Volume
| Issue : 4 | Page : 168-171
Histopathological patterns of skin adnexal tumours in Ibadan, South-West Nigeria
Omolade O Adegoke, Mustapha Akanji Ajani
Department of Pathology, College of Medicine, University of Ibadan and University College Hospital, Ibadan, Oyo State, Nigeria
|Date of Submission||06-Apr-2021|
|Date of Decision||17-Jul-2021|
|Date of Acceptance||26-Aug-2021|
|Date of Web Publication||11-Jan-2022|
Mustapha Akanji Ajani
Department of Pathology, College of Medicine, University of Ibadan and University College Hospital, Ibadan, Oyo State
Source of Support: None, Conflict of Interest: None
Background: Skin adnexal tumours (SATs) are tumours that differentiate towards one or more of the adnexal structures of the skin. The aim of this study was to determine the incidence of SATs in Ibadan and to correlate them with age, sex and anatomic location. Methods: This is a 10-year retrospective study of all SATs in the Department of Pathology, University College Hospital, Ibadan. The clinicopathological data were obtained from the department's records for the given period. Haematoxylin and eosin-stained sections obtained from formalin-fixed paraffin-embedded tissue blocks were examined to confirm the diagnosis and special stains such as periodic acid Schiff staining done where necessary. Cases of SATs were further classified into benign and malignant tumours. Results: Twenty-seven cases of SATs were reviewed over the study period. Tumours from the sweat glands formed the largest group (55.6%) with trichoepithelioma being the most common subtype, followed by tumours with follicular differentiation (40.7%) and sebaceous tumours (3.7%). There was a slight female predominance with a male-to-female ratio 1:1.07. The highest number of tumours was seen in the fourth decade of life (23%). Benign tumours made up the majority of cases (85.2%). The most common location was the head and neck with 40.8% of cases. Conclusion: SATs are not uncommon among Nigerian patients. These tumours are mostly benign and are present commonly in the head and neck location.
Keywords: Head and neck, sebaceous carcinoma, skin adnexal tumours, trichoepithelioma
|How to cite this article:|
Adegoke OO, Ajani MA. Histopathological patterns of skin adnexal tumours in Ibadan, South-West Nigeria. Hamdan Med J 2021;14:168-71
| Introduction|| |
Skin adnexal tumours (SATs) are tumours that differentiate toward one or more of the adnexal structures of the skin. Historically, these tumours were classified on the basis of whether their histologic structures resembled hair follicles, sebaceous glands, apocrine glands or eccrine glands. Each of the aforementioned categories has benign and malignant subtypes. This classification albeit useful presents unique challenges as SATs are a heterogeneous group and tumours may exhibit histologic features of two or more appendageal types. The current concepts in SATs suggest that tumorigenesis arises from the proliferation and differentiation of pluri-and multipotent stem cells in the epidermis or adnexal structures and may express one or more types of appendageal differentiation in varying degrees.
There is no well-established aetiology for most adnexal tumours, although some are associated with inherited syndromes, particularly sebaceous carcinoma associated with the Muir − Torre syndrome and trichoepithelioma which may be inherited as an autosomal dominant trait known as the Brooke–Spiegler syndrome. Malignant transformation is rare but can occur. Basal cell carcinomas have also been described arising in association with multiple trichoepitheliomas. It may co-exist with other SATs such as syringoma as well as in association with melanomas and naevi. Some possible triggers for SATs include ultraviolet exposure, radiation, immunosuppression and antecedent trauma.
Benign SATs far outnumber their malignant counterparts and most of them arise de novo, although some may arise in pre-existing lesions such as nevus sebaceous. Most malignant cutaneous adnexal tumours (MCATs) also arise de novo although rarely apocrine carcinomas may arise in naevus sebaceous and porocarcinoma, spiradenocarcinoma or hidradenocarcinoma may arise in a pre-existent poroma, spiradenoma or hidradenoma, respectively.
Of particular importance amongst MCATs is Paget's disease. It is an intraepidermal adenocarcinoma characterised by large atypical and pale staining cells scattered throughout the epidermis either as single cells or in small clusters. Mammary Paget disease (MPD) typically presents as a demarcated, thickened, eczematoid, erythematous weeping or crusted lesion with irregular borders on the nipple and areola, and in almost all cases constitutes skin involvement by an underlying in situ or invasive ductal carcinoma of the breast. Rarely, there is no underlying breast tumour found and the tumour appears to have originated within the nipple epidermis. The clinical features are such that they can be confused clinically with generalised inflammatory skin conditions such as eczema and psoriasis.
Extramammary Paget disease is a scaly erythematous eruption affecting apocrine gland bearing areas of the skin, mainly the female and male genital areas. The majority of cases are thought to represent an apocrine adenocarcinoma in situ. In a subset of cases, there is an underlying internal malignancy. The skin manifestations of the two types are clinically and histologically indistinguishable from each other. In long-standing cases, the appearance may be modified by repeated trauma making it more difficult to recognise. However, just like in MPDs, the clinical features are non-specific and can easily be misdiagnosed as an inflammatory or infective lesion.
Most benign SATs present as papules or nodules and are difficult to distinguish clinically from other cutaneous lesions. Although some benign tumours may ulcerate, ulceration is usually a sign of malignancy. In general, the clinical features of SATs are mostly indistinguishable from other skin lesions; therefore, histopathology is essential to making a diagnosis, and sometimes, even this is difficult as these tumours may differentiate along multiple histological lines.
| Methods|| |
This was a 10-year retrospective study of SATs in the Department of Pathology, University College Hospital, Ibadan. The clinicopathological data were obtained from the surgical day book for the given period. Haematoxylin and eosin-stained sections obtained from formalin-fixed paraffin-embedded tissue blocks were examined to confirm the diagnosis and special stains like PAS done if necessary. Cases of SATs were further classified as either benign or malignant and then according to their line of histologic differentiation using the WHO classification of skin tumours.
| Results|| |
Twenty-seven cases of SATs were reviewed over the study period. Tumours from the sweat glands formed the largest group (15/27, 55.6%), followed by tumours with follicular differentiation (11/27, 40.7%) and sebaceous tumours (1/27, 3.7%). Females were slightly more than males with a M: F ratio 1:1.07. Tumours were observed from the first decade to the ninth decade (3–80 years). The mean age was 36.6 years, and the highest number of tumours was seen in the 31–40 age group (6/27, 23%) [Table 1]. Benign tumours made up the majority of cases (23/27, 85.2%) while there were just four malignant tumours (14.8%). Trichoepitheliomas [Figure 1] were the most common follicular derived tumours making up 7 out of 11 cases. There were only four malignant tumours in this cohort, a porocarcinoma, one sebaceous carcinoma [Figure 2] and two cases of Paget's disease. Syringomas were the most common sweat gland derived tumour with 4 out of 14 cases. Other sweat gland tumours include eccrine tubular adenoma and eccrine poroma [Figure 3] and [Figure 4]. The most common location was the head and neck with 40.8% of cases followed by the limbs with 22.2% and the trunk and abdomen with 11.1% [Table 2] and [Table 3]. In 7 (25.9%) of the cases, the location of the tumour was not known precisely.
|Figure 3: Photomicrograph showing eccrine tubular adenoma (H and E, ×100)|
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| Discussion|| |
SATs are rare cutaneous tumours, with only 27 cases reported in our institution over a 10-year period. Sharma et al. reported 56 cases over a 7-year period in India while Rabie and Omar reported 18 cases over a 4-year period in Egypt. In Nigeria, a 10-year review by Dele et al. in Benin revealed only 6 cases of cutaneous SATs, while Samaila in Zaria reported 52 cases over a 15-year period. In our study, the male-to-female ratio was almost equal suggesting that hormonal factors do not have any effect on the occurrence of these tumours. Pujani et al. reported a M: F ratio of 0.92:1 while Samaila reported an equal number of males and females, and this was similar to other studies reviewed. These tumours can be seen in all age groups with a peak age of occurrence among young adults. This was shown in our study where the mean age was 36.6 years with a peak in the 31–40 years' age group.
The head and neck has been shown to be the most common location of SATs and this can be explained by the presence of numerous pilosebaceous units as well as eccrine and apocrine sweat glands in this area. In our study, 55% of tumours were located in this region with more than half of these on the face.
Most cases are benign; Sharma et al. reported that 80.36% of cases reviewed were benign while Omar reported that 94.4% of cases were benign with only one malignant case in the series. Our study was similar with 85.2% of the cases being benign. A study from the SEER database in the United States over a 5-year period showed incidence rates for MCATs to be 5.1 per 1 million person years. This illustrates how rare MCATs are. Malignant tumours in our study made up just 14.8% of cases in this study and were consistent with studies from Nigeria and other parts of the world.
Tumours derived from the sweat glands appear to be the predominant type in our study. Pujani et al. reported that 56% of tumours were derived from the sweat glands followed by the hair follicles and the sebaceous glands while Samaila in Zaria reported the sweat glands as the commonest origin with 78.8% followed by the sebaceous gland 13.5% and hair follicle 7.7%. The findings were similar in our study with more than half of the tumours being sweat gland tumours, this was followed by follicular tumours and sebaceous carcinoma. Among the sweat gland-derived tumours, syringomas were the most common in our study while trichoepitheliomas were the most common of the hair follicle-derived tumours.
Some reports such as that by Heysari in Iran reported high numbers of sebaceous tumours; however, it is noted that cutaneous adnexal lesions such as sebaceous nevus of Jadasson and steatocystoma were included in this cohort. Nevus sebaceous of Jadasson is regarded as a harmatoma and is not included in the WHO classification of SATs. As rare as SATs are, the malignant forms are even rarer. In our study, only four cases were seen. One each of sebaceous carcinoma and porocarcinoma and two cases of Paget's disease. Sebaceous carcinoma appears to be the most common malignancy of skin adnexal structures in various studies.,
| Conclusion|| |
The incidence of benign SAT is more than the malignant ones, although there is low incidence of the SATs in our population. SATs are a heterogeneous group of tumours with clinical features indistinguishable from other unrelated skin lesions. Histopathology is required to make a diagnosis and the attending pathologist must have a high index of suspicion so as not to miss this diagnosis, especially as these tumours may sometimes differentiate along multiple lines or occur in association with other cutaneous tumours or lesions.
The institution gives a waiver for ethical approval for this study because we used anonymized data. The data obtained did not infringe on the rights of subjects and did not violate the principles of confidentiality.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]