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Year : 2019  |  Volume : 22  |  Issue : 12  |  Page : 1752-1757

Oral mucosal melanoma in four Nigerian teaching hospitals

1 Oral Pathology Unit, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Nigeria, Ile-Ife, Nigeria
2 Department of Oral and Maxillofacial Pathology/ Biology, Faculty of Dental Sciences, College of Medicine, University of Lagos, Ile-Ife, Nigeria
3 Department of Oral Pathology, Faculty of Dentistry, University of Ibadan, Ile-Ife, Nigeria
4 Department of Oral Maxillofacial Surgery and Oral Pathology, Faculty of Dentistry, College of Health Sciences, Obafemi Awolowo University, Ile-Ife, Nigeria
5 Oral Pathology Unit, Department of Oral and Maxillofacial Surgery, Clinical Dental Services, University of Nigeria Teaching Hospital, Ituku-Ozalla, Enugu, Nigeria

Date of Submission27-Mar-2019
Date of Acceptance21-Aug-2019
Date of Web Publication3-Dec-2019

Correspondence Address:
Dr. M C Nwoga
Oral Pathology Unit, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Nigeria
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njcp.njcp_176_19

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Background: Oral mucosal melanoma (OMM) is a malignant lesion of melanocytes of oral epithelium. The prevalence in four Nigerian teaching hospitals is reported. Aims: This study shows the hospital based prevalence and the clinicopathologic features of OMM in four Nigerian teaching hospitals. Subjects and Methods: A retrospective study of patients diagnosed with OMM in four teaching hospitals in Nigeria was carried out. All records of patients with orofacial lesions from 1969 to 2016 were identified and retrieved from the archives of four oral pathology departments. The biodata and relevant clinicopathologic information of those diagnosed with OMM were reviewed. Data analysis was done with SPSS for Windows, version 20. Results: There were 10,877 orofacial lesions managed during the period. Oral malignant lesions constituted 14.4% (1,552/10,877). OMM was diagnosed in ten patients with prevalences of 0.09% and 0.6% of all orofacial lesions and oral malignancies, respectively. There was a male predilection of 4:1 and a mean age of occurrence of 53.8 (±12.6) years. The palate was the most frequent site, 40.0% (4/10). Regional lymph nodes were hard, fixed, or matted in 50.0% (5/10) of patients and distant metastases observed in 20.0% (2/10). Among those followed up, only one was documented alive after 6 months. Amelanotic OMM, 20.0% (2/10) did not show ulceration or regional and distant metastasis. Conclusions: OMM has a low prevalence but with poor prognosis. Amelanotic OMM showed less clinical aggression. Early diagnosis and prompt treatment are recommended.

Keywords: Melanocyte, Nigeria, oral melanoma, oral mucosa

How to cite this article:
Nwoga M C, Effiom O A, Adeyemi B F, Soyele O O, Okwuosa C U. Oral mucosal melanoma in four Nigerian teaching hospitals. Niger J Clin Pract 2019;22:1752-7

How to cite this URL:
Nwoga M C, Effiom O A, Adeyemi B F, Soyele O O, Okwuosa C U. Oral mucosal melanoma in four Nigerian teaching hospitals. Niger J Clin Pract [serial online] 2019 [cited 2022 Dec 2];22:1752-7. Available from:

   Introduction Top

Oral mucosal melanoma (OMM) is a malignancy of the melanocytes of the oral mucosa. The prevalence varies in different populations and races.[1] OMM constitute 1-8% of malignant melanomas,[2] but only 0.5% of oral malignancies.[3] An incidence of 1.2 cases per 10 million per year is reported.[4] The lesions were already advanced by the time they become symptomatic,[5] and there is a 5-year survival rate of 0-20%.[6] There are few studies on the prevalence and clinicopathologic features of OMM in Nigeria.

   Subjects and Methods Top

The records of Oral Pathology Departments of four Nigerian Teaching Hospitals were assessed for patients with oral and maxillofacial lesions. The case files of patients with records of oral lesions confirmed by histology as OMM were retrieved from the departmental archives. The study involved four major tertiary health institutions in southern Nigeria. They represent regional referral health centers with oral and maxillofacial pathology services. They receive and manage patients with oral and maxillofacial lesions from large sections of population in Southern Nigeria. The investigation covered a period ranging from 5 to 47 years, depending on the year of establishment of the oral pathology service at each hospital. This study period extended therefore, from 1969 to 2016 for the hospital with the longest period of oral pathology service. Records were checked for presence of melanoma at other sites apart from the oral mucosa and history of therapy for melanoma. This was done to establish the oral lesion as a primary or metastatic disease.

The inclusion criteria

All cases with histological or immunohistochemical diagnoses of OMM were included in this study.

The exclusion criteria

All benign oral pigmented lesions and melanoma of other sites were excluded from the study.

The following data were retrieved from individual patients' records: biodata (gender, occupation, age at presentation), and relevant clinicopathologic information (duration of lesion, location, ulceration, complaint of pain, and evidence of metastases). Also, documentation of history of diagnosis or treatment of any other site was sought. The hematoxylin and eosin (H and E) stained slides of the patients were reviewed. Similarly, tissue blocks were retrieved and new slides prepared where archival H and E stained slides were faded. The results of immunohistochemical studies for amelanotic cases which stained positive for melanocytic marker HMB45 and protein S100 were accepted. Immunohistochemical study was not repeated. Any diagnosis of amelanotic OMM without a confirmatory study was to be confirmed with an immunohistologic study. The primary outcome was positive histopathologic diagnosis of OMM. All the cases were confirmed based on either H and E staining or by immunohistochemical study. The secondary outcomes were the clinical features of gender, age, occupation, tumor site, duration, clinical lesion color, pain, ulceration, bleeding from the tumor, recurrence, regional lymph node involvement, distant metastases, and posttreatment survival period. The clinical staging of OMM was achieved through direct visualization and palpation, and histological studies for all cases.

The clinical staging of oral mucosal melanoma disease was based on the American Joint Committee on Cancer (AJCC) of mucosal melanoma disease of the head and neck.[7] Four clinical stages are described: III, IVA, IVB, and IVC. They are based on the anatomic TNM classification, where the T (primary tumor) has only T3, T4a, and T4b.

The histological grading of the tumors was based on the Western Society of Teachers of Oral Pathology (WESTOP) criteria.[8] The WESTOP system has three classes: melanoma-in-situ, invasive melanomas, and a combined pattern of in-situ and invasive features.

The microscopic examination and diagnoses of the OMM specimens were based on demonstration of proliferating malignant melanocytes that appeared as epithelioid, plasmacytoid, or spindle-shaped cells, arranged in nests, sheets, alveolar, or organoid patterns. The observation of malignant melanocytes at the epithelial-connective tissue junction with proliferation and invasion along the basal cell layer into the dense connective tissue stroma was considered diagnostic. Melanotic OMM was diagnosed where all or some of the malignant cells have variously sized dark brownish melanin pigments, [Figure 1] and [Figure 2]. Amelanotic variants of OMM showed similar histologic features with no visible melanin pigment.
Figure 1: Palatal lesions of oral mucosal melanoma

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Figure 2: Photomicrograph showing invasive large pleomorphic malignant melanocytes deep in the stroma, with numerous deposits of melanin pigments (hematoxylin and eosin, magnification × 40)

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The proportions, frequencies, percentages, and mean with standard deviation were calculated for the descriptive variables using Statistical analytical package for social sciences (SPSS) for Windows Version 20.0, Chicago: SPSS Inc. The means and standard deviations of continuous variables, the frequency tables of categorical variables, and association of categorical variables using chi square tests were determined. The test of significance was set at P = 0.05

   Results Top

A total of 10,877 orofacial biopsy specimens were received and processed during the period. The period of oral pathology services in the four tertiary health institutions were 6, 16, 27, and 48 years. The total orofacial biopsies with histology reports were 308, 1184, 3059, and 6326, respectively. Malignant lesions constituted 14.4% (1,552/10,877) of all specimens, among which were three cases of cutaneous melanoma of the facial region. Primary OMM occurred in ten patients with a prevalence of 0.09% (10/10,877) of oral biopsies and 0.6% (10/1,552) of oral and maxillofacial malignancies. Eight cases, 80.0% (8/10) were diagnosed as melanotic OMM with routine H and E stains only. Two cases, 20.0% (2/10) required additional immunohistochemical investigations. They were positive for HMB-45 and S-100, thus were diagnosed as amelanotic OMM. None of the cases had a history of a prior diagnosis of melanoma of the skin or any other site or therapy for melanoma before diagnosis of OMM was made. One of the patients was an albino. There was no case documented as recurrent. Some of the general features of the ten cases of OMM are shown in [Table 1].
Table 1: Features of oral mucosal melanoma cases

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Male to female ratio was 4:1. The patients' ages ranged from 38 years to 80 years, with a mean age of 53.8 ± 12.6 years. Concerning occupation of subjects, there were two peasant farmers, a petty trader, a herbalist, a retired nurse, a pastor, an unemployed, and three others with unspecified occupation. There was no significant association between occupation and the risk of OMM, P = 0.56. All the lesions involved the mucosa of upper jaw and the related soft and hard tissues [Table 2].
Table 2: Summary of clinicopathologic features of patients with oral mucosal melanoma, n=10

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Of the nine patients with information about the color of the lesions, 55.6% (5/9) were black [Figure 1]. Others were brownish-black, greenish, gray, and reddish, all of which constituted 44.4% (4/9) of the lesions, [Table 1]. There was a significant association between OMM and coloration especially black/brownish pigmentation P = 0.04. The mean duration of lesion was 12.7 ± 10.5 months. Of the ten cases, 70.0% (7/10) had ulceration. The ulcers had rolled edges with granular surfaces. There was a significant association between ulceration and melanotic OMM, P = 0.03. Spontaneous hemorrhage of the tumor was reported in 40.0% (4/10), while 80.0% (8/10) reported having pain.

There were nodal metastases in 50.0% (5/10) of the patients indicated by hard, fixed, or matted regional lymph nodes. Distant metastases to the lungs were reported in 20.0% (2/10). All the cases were classified as invasive melanoma based on the WESTOP system. All the patients presented with stage IV disease based on the American Joint Committee on Cancer (AJCC) staging system for mucosal melanoma, [Table 2].

A review of patients' management revealed that 30.0% (3/10) did not receive treatment because they failed to return to the hospital after being diagnosed of OMM, receiving counseling or after being scheduled for surgery. However, 70.0% (7/10) of the patients were treated.

Of the seven patients who received treatment, 71.4% (5/7) had surgery alone, 14.3% (1/7) had chemotherapy alone, and 14.3% (1/7) had both surgery and radiotherapy. Only 49.2% (3/7) of patients who received treatment attended any post-therapy review and follow-up. They did so for an average period of 5.3 months. At 6-months post-treatment, only one (33.3%) of the three patients was recorded to be alive, while the other two were lost to follow-up.

Comparison of Amelanotic and Melanotic OMM

Although there were only two amelanotic cases in the series, they presented with the longest duration at diagnosis of 36 and 12 months, [Table 3]. They were not associated with regional or distant metastases at the time of diagnosis. Duration of lesion did not show any statistically significant relationship with regional lymph node involvement P = 0.7, nor with the lesion P = 0.2.
Table 3: Comparing features of amelanotic and melanotic OMM, n=10

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   Discussion Top

OMM accounted for 0.09% and 0.6% of all orofacial lesions and oral malignancies respectively in this study. This is contrary to the opinion of some authors that due to the increased density of intraoral melanin pigmentation, Africans have a higher prevalence of OMM.[2] However, reports show higher values of oral mucosal melanoma among Asians especially the Japanese with 11-12.4% of all melanomas.[1]

The mean age of 54 years in this study is slightly lower but comparable with reports of mean age range of 55-57 years.[8],[9] In this study, OMM was more common in male patients. This conforms with results by other authors,[8],[9],[10] but contrasts with frequent observations of equal gender distribution in cutaneous melanoma.[11],[12] The suggested reasons for the greater male preponderance included frequent tobacco chewing, smoking, and exposure to formaldehyde.[13],[14] Similar to other societies, male patients in Nigeria use tobacco in various forms. Other reported risk factors for development of oral malignant melanoma include race, culture, and geographic location.[5] Patients in this study, according to their occupation, were mostly low-income earners, an observation similar to the finding of Hasan et al.[15] The majority of these are exposed to sunlight, though studies have not established any strong association between OMM and exposure to ultraviolet radiation.[16]

Oral melanoma occasionally clinically mimics various common benign oral pigmented lesions, such as amalgam tattoos, nevus, and melanotic macule.[4],[9] Melanin is a pigment which appears brown, red, or green due to the physical properties of light absorption and reflection (Tyndall light phenomenon).[17] Nambiar et al. in a review observed that melanomas present various clinical colors, such as black, gray, purple, and reddish.[2] Pigmented cases, as found in this study, were more frequently reported.[13] The color of the lesions in this study being mostly black is consistent with that reported by Baker et al.[18] Coloration of lesions facilitated early identification. Amelanotic OMM, however, may appear red, white, or have same color as the oral mucosa.[17] About 40% of mucosal melanomas of the head and neck region are amelanotic,[7] but the proportion of these constituted by OMM was not reported. In this study, 20% of OMM were amelanotic. Amelanotic melanomas are believed to be biologically more aggressive than pigmented melanomas.[19] Though the number of cases was low in this series, amelanotic OMM appeared to exhibit less clinical aggression than melanotic OMM based on the absence of ulceration, better clinical stage despite longer duration before presentation, absence of regional nodal involvement, and absence of metastasis.

The predilection of OMM for the maxillary region especially the palate in this series is consistent with reports from other studies.[4],[13],[16],[18] The delayed presentation and diagnosis may be attributed to the intraoral location and the initial painlessness of the lesion. Pain, ulceration, and spontaneous bleeding were observed in majority of our patients. These features often are indicative of advanced disease.[5],[20] OMM is generally aggressive, with rapid growth and early metastatic spread, a feature attributed to the complex anatomy and the rich lymphatic system of the oral region.[21] The mean delay of 12.7 months before presentation in this series, contributed to the development of regional and distant metastases, and poor prognosis. The occurrence of hard, fixed, and/or matted regional lymph nodes in 50.0% of the cases was higher than the 15.0% estimated in literature[7] and conforms with the high metastatic potential of OMM.[13],[15],[16]

Although most of our cases were simply diagnosed with routine H and E stained slides, the histological diagnosis of OMM may occasionally be challenging for pathologists due to the presence of amelanotic variants. Examination of tissues stained with H and E remains the gold standard for definitive diagnosis of melanotic cases of OMM.[1],[2],[22] Amelanotic melanoma and other difficult melanotic melanoma cases require additional immunohistochemical investigations such as S-100, gp-100, HMB-45, MITF, and MART-1 for diagnosis.[1],[2],[4],[19]

A multimodal treatment approach for OMM is recommended with surgical excision as the primary mode followed by radiotherapy and occasionally chemotherapy. Chemoimmunotherapy is a novel treatment modality still under consideration.[2] Diseases restricted to the mucosal tissues and diagnosed at AJCC Stage III offer the best prognosis with surgical resection and radiotherapy.[7] Majority of the Nigerian citizens have no health insurance. Thus, the responsibility of financing the primary and adjuvant therapy rests on patients and their relatives. Therefore, the clinicians' recommendations of therapy were predicated on the stage of the disease, presence of metastases, and the financial capacity of the patient. In this study, the therapy that combined radical surgery with adjuvant radiotherapy and palliative chemotherapy for the few patients who received treatment, did not improve prognosis. Although a low 5-year survival rate of 0--20% has been reported,[5],[6] the cases treated in the present study were not followed up beyond 8 months postsurgery due to patients' failure to keep review appointments. The available record only showed that at 6-months post-treatment, only one (33.3%) of the three patients was alive. The poor outcome in this study may be attributed to the advanced stage of disease at presentation with regional and distant metastases, poor enlightenment of patients and the delayed treatment often associated with sourcing fund for treatment. There were additional constraints when patients travel to referral centers in other states in the country for radiotherapy.

The rarity of OMM, reliance on case-note documentation, and incomplete record keeping were limitations to this study. Other factors important in predicting performance and survival of patients, such as comorbidities, alcohol, and tobacco abuse were inadequately documented. The low prevalence of the OMM may account for the few Nigerian studies. Goubran et al., more than 4 decades ago, reported two Nigerian cases of melanoma of the face and mouth.[23] Another publication by Adisa et al. reported a single case of oral amelanotic melanoma.[19] A relatively recent publication by Adeyemi et al. recorded five oral cases in a review of 31 melanomas of head and neck region.[24] The authors did not focus on clinical features and management of OMM. Most other Nigerian studies focused on cutaneous melanoma.[11],[12] The present study is the largest on OMM in Nigeria known to the authors. Further studies comparing the clinical and biological behavior of melanotic and amelanotic OMM will be required to confirm the findings in this study.

   Conclusion Top

OMM has a low prevalence in the Nigerian population studied, and it was characterized by late presentation, high metastatic potential, and poor prognosis. A high index of suspicion for all asymmetrical oral pigmented lesions is required for early diagnosis and prompt treatment. Clinicians and policymakers should work toward improving oral health awareness and oral examination.

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Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]

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