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Oral melanoacanthoma: a case report and review of the literature
© Lakshminarayanan and Ranganathan; licensee BioMed Central Ltd. 2009
Received: 01 February 2008
Accepted: 13 January 2009
Published: 13 January 2009
Oral melanoacanthoma is a rare, benign pigmented lesion characterized clinically by the sudden appearance and rapid growth of a macular brown-black lesion and histologically by acanthosis of the superficial epithelium and proliferation of dendritic melanocytes.
We present a case report of oral melanoacanthoma in a 24-year-old Asian Indian man. He presented with an intra-oral brown macular lesion on the left buccal mucosa with a duration of one and a half months. Microscopic examination revealed acanthosis of stratified squamous surface epithelium and dendritic melanocytes diffusely distributed in the epithelium; the Masson-Fontana silver impregnation technique was used to demonstrate the dendritic melanocytes. Based on the history, clinical features and histological presentation, the lesion was diagnosed as melanoacanthoma.
This is the first reported instance of oral melanoacanthoma in the Indian sub-continent. This report details the course of the lesion from diagnosis to its resolution. Melanoacanthoma must be differentiated from other intra-oral pigmented lesions and biopsy may be required to rule out melanoma.
No. of patients
Matsuoka et al. *
Schneider et al. 
Wright et al. *
Goode et al. 
Buccal, labial, palatal, alveolar mucosa and gingiva
Frey et al. 
Sexton and Maize 
Whitt et al. *
Horlick et al. *
Zemtsov and Bergfeld 
Heine et al. *
Buccal mucosa – bilateral
Chandler et al. 
Fatazedah and Sirois 
Fornatora et al. *
Buccal (including bilateral), gingival, labial and palatal mucosa; retromolar pad, floor of the mouth
Buchner et al. 
Buccal, labial and lingual mucosa
Kauzman et al. 
Andrews and Trask 
Carlos-Bregni et al. 
Buccal mucosa, gingiva, palate
The brownish-black macular lesion on the left buccal mucosa was well demarcated from the surrounding mucosa with regular, well-defined borders. The lesion extended anteriorly from the region of the mandibular first molar (36) to the mandibular left canine region. It measured 25 mm antero-posteriorly and had a maximum width of 16 mm supero-inferiorly. The lesion was not tender, did not blanch under pressure and was not fixed to the underlying mucosa.
The term melanoacanthoma refers to a lesion exhibiting a proliferation of dendritic melanocytes throughout the surface epithelium. Cutaneous melanoacanthoma is also known as pigmented seborrheic keratosis .
Oral melanoacanthoma is a benign, reactive process and is unrelated to cutaneous melanoacanthoma. The reported age of presentation ranges from 9 to 77 years, with a mean age of 29 years [3, 4, 12]. The lesion is most predominantly observed among black patients, though occurrences have been observed among Caucasians, Hispanics and Asians [1, 4, 12–14]. Oral melanoacanthomas show a female predilection, with a male to female ratio of 2:1 [1, 2, 14]. The etiology has been largely attributed to local irritation or even mild trauma [3, 14]. The intra-oral site most commonly affected is the buccal mucosa but involvement of other sites such as the mucosa of the lip, palate, gingiva and alveolar mucosa has also been reported (Table 1). Clinically, the lesion is a flat or slightly raised black or brown macule and may rapidly increase in size, ranging from a few millimeters to several centimeters [1, 12, 13]. The lesions are usually solitary and well circumscribed though a few authors have reported bilateral or multiple (Table 1) melanoacanthomas. Oral melanoacanthomas are usually asymptomatic and are not neoplastic. The other lesions to be considered in the differential diagnosis are smoker's melanosis, drug induced pigmentation, Addison's disease, melanotic macule, pigmented nevi – junctional, intramucosal, compound, Spitz nevus, postinflammatory melanosis and oral melanoma. A biopsy is mandatory to rule out melanoma and to alleviate patient apprehension. Histologically, melanocytes which are usually restricted to the basal layer are found distributed throughout the epithelium. These melanocytes exhibit prominent dendritic processes and are immunoreactive for S-100, Melan-A/Mart-1, HMB-45 and Tyrosinase . Other dendritic cells in the oral mucosa are the Langerhans' cells which are antigen presenting cells of the immune system, usually distributed in the superficial epithelium and are demonstrated on immunohistochemistry by S-100 or CD1a. The adjacent connective tissue exhibits chronic inflammatory cell infiltrate. The presence of eosinophils among the inflammatory cells is not a universal feature and may not be essential for the diagnosis of oral melanoacanthoma. Once diagnosis is established, no further treatment is required, with some cases exhibiting spontaneous regression after biopsy . It has been suggested that this entity be renamed melanoacanthosis or oral melanotic macule – reactive type, since the term melanoacanthoma is suggestive of a neoplastic process .
In our patient, the etiology of the lesion may be attributed to the incident of trauma during the restorative procedure. It may be safely assumed that GIC did not contribute to the cause of the lesion since the patient has multiple restorations with the same material and the adjacent sites did not exhibit any lesion.
To the best of our knowledge, this is the first case of oral melanoacanthoma in the Indian subcontinent and the second case of melanoacanthoma reported in an Asian Indian. In the present instance, a biopsy was performed to alleviate the patient's anxiety and as reported, the lesion regressed following biopsy. Thus, melanoacanthoma must be considered in the differential diagnosis of rapidly progressing pigmented lesions of the oral cavity and requires a histopathological diagnosis to rule out melanoma.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
We thank our Principal, Dr. S. Ramachandran, for encouraging and facilitating the publication of this case report and Dr. Sai Prasanth, for having referred the case.
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