An unusual clinical presentation of gingival melanoacanthoma.

Gingival melanoacanthoma is a rare, benign pigmented lesion characterized clinically by sudden onset and rapid growth of a macular brown black lesion and histologically by acanthosis of superficial epithelium and proliferation of dendritic melanocytes. This article reports a previously undescribed case of pigmented unilateral diffuse gingival enlargement, which on histopathological examination proved to be melanoacanthoma. Intraoral examination revealed pigmented unilateral diffuse gingival enlargement in relation to second and third quadrants buccally, palatally/lingually. Based on these clinical findings, gingivectomy was performed and the excised tissue was sent for biopsy. Microscopic examination revealed acanthotic and parakeratotic surface epithelium with dendritic melanocytes distributed in basal and suprabasal layers of the epithelium. 1 year follow-up recall revealed no recurrence of lesion at the surgical sites. Our patient exhibits an unusual clinical presentation of melanoacanthoma of gingiva. Pigmented gingival overgrowth of recent origin and without any etiologic factors warrants histopathologic examination.

INTRODUCTION

Melanoacanthoma is a benign and uncommon pigmented mucocutaneous lesion characterized by dendritic melanocytes dispersed throughout the epithelium.[1] Goode et al. published the first retrospective review of 10 cases of oral melanoacanthoma reported in the literature in 1983.[2] Oral melanoacanthoma usually occurs on the buccal mucosa (51.4%), with fewer lesions originating on the palate (22.2%), lips (15.2%) and gingiva (5.6%).[3]

Oral melanoacanthoma is seen almost exclusively in blacks, shows a female predilection and is most common during the third and fourth decade of life. The lesion is smooth, flat or slightly raised, dark brown to black in color. Lesions often demonstrate a rapid increase in size and they occasionally reach a diameter of several centimeters within a period of few week, potentially masquerading as a melanoma.[4]

To the best of our ability, a comprehensive review of literature on gingival melanoacanthoma revealed 12 cases mostly involving singular lesions [Table 1]. Herein, we present an unusual case report of gingival melanoacanthoma, which presented clinically as pigmented unilateral gingival enlargement.

Table 1

Reported cases of gingival melanoacanthomas

CASE REPORT

Clinical findings

A 13-year-old male patient attended the Department of Periodontics, Mahatma Gandhi Post Graduate Institute of Dental Sciences, Pondicherry, in May 2011 for gingival enlargement and difficulty in mastication. The patient was otherwise healthy. He first noticed enlargement 6 months earlier along the buccal aspect of tooth 26, which increased in size slowly to the present clinical picture. The clinical examination was significant for the presence of pigmented diffuse gingival enlargement along buccal and palatal aspects of 24, 25, 26, 27 and lingual aspects of teeth 34, 35, 36, 37 [Figure 1]. Gingival enlargement was extending up to middle third of the crown of tooth 24, partially covering the occlusal surface of teeth 25, 26 and completely covering the tooth 27 [Figure 2] and extending up to occlusal surface of teeth 34, 35, 36, 37. The gingival enlargement was firm in consistency, painless, brownish black in color with well-defined borders and there was no associated erythematous background.

Figure 1

Melanoacanthoma on the maxillary posterior gingiva

Figure 2

Melanoacanthoma on the occlusal surface of 26, 27

Other significant dental findings included root canal treated fractured tooth 21 and congenitally missing tooth 23. Patient's oral hygiene was deemed satisfactory. There was no significant medical history. Patient was not having any associated cutaneous pigmentary changes. Based on the clinical findings, provisional diagnosis of idiopathic gingival enlargement was made and gingivectomy was planned for the treatment.

Treatment and follow-up

Patients’ parents provided oral consent for treatment prior to the initial and additional tests and the dental treatment that followed. Routine blood investigations were found to be within normal limits. Gingivectomy was performed under local anesthesia on the buccal aspect of II quadrant [Figure 3] and the excised tissue was sent for biopsy [Figure 4]. One week later, gingivectomy was performed on the palatal aspect of II quadrant followed by lingual aspect of III quadrant after 1 week. Kirkland knives were used for incisions on the facial and lingual surfaces. Orban periodontal knives were used for interdental incisions. Patient experienced an uneventful post-operative recovery [Figure 5] at 1 year recall examination there was no recurrence of gingival enlargement at the surgical sites [Figure 6]. Patient will continue to be monitored on a 6 month basis and any new gingival enlargement/lesion will undergo histopathologic investigation.

Figure 3

Gingivectomy carried out in II quadrant – Buccal aspect

Figure 4

Excised tissue after gingivectomy

Figure 5

Surgical area 2 weeks post-operatively

Figure 6

One year follow-up with no recurrence

Histopathological findings

Histopathological examination revealed numerous dendritic melanocytes distributed in basal and suprabasal layers of acanthotic epithelium. Melanocytes did not display any cytologic atypia [Figure 7]. The connective tissue was normal except for the presence of occasional eosinophils. There was no spillage of melanin pigment/melanocytes in subepithelial zone [Figure 8]. Histopathologic diagnosis of oral melanoacanthoma was rendered.

Figure 7

Microscopical features of melanoacathoma showing dendritic melanocytes distributed throughout acanthotic epithelium (H and E; original magnification ×100)

Figure 8

Melanoacanthoma showing dendritic melanocytes distributed in basal and suprabasal layers of epithelium with normal connective tissue (original magnification ×45)

DISCUSSION

Oral melanoacanthoma is a benign reactive process and shows a rapid increase in size that reaches several centimeters within a few weeks. The reported age of presentation ranges from 6 to 77 years with a mean age of 29 years.[713] Though the lesion is most predominantly observed among black patients, occurrences have also been observed among Caucasians, Hispanics and Asians.[213] The lesion usually occur on the buccal mucosa, but involvement of other sites such as the mucosa of lip, palate, gingiva and alveolar mucosa has also been reported. Clinically the lesion is flat or slightly raised black or brown macule.[13] The lesions are usually solitary and well-circumscribed, though a few authors have reported bilateral or multiple melanoacanthoma.

With the addition of featured case 13 patients with gingival melanoacanthoma have been reported [Table 1]. To the best of our knowledge, this is the first comprehensive case of gingival melanoacanthoma presented clinically as pigmented diffuse gingival enlargement. At 1 year follow-up examination of our patient revealed no recurrence of any of the excised lesions.

The pathogenesis of oral melanoacanthomas is not yet clear, although these lesions are considered a reactive phenomenon.[10141516] The etiology has been largely attributed to local irritation or even mild trauma.[4] Trauma was reported with only one case of gingival melanoacanthoma.[612] There were no attributable etiologic factors with the present case. There may be an idiosyncratic predisposition toward the formation of oral melanoacanthoma in the patient.

Histopathological examination did not reveal nuclear pleomorphism, hyperchromatism and nests of melanocytes, suggestive of malignancy. There was normal connective tissue with no spillage of melanin pigment/melanocytes in subepithelial zone. In the light of the history, clinical features and the histopathologic examination, the final diagnosis of oral melanoacanthoma was made.

The clinical differential diagnosis of localized brown to black gingival pigmentations include smoker's melanosis, drug induced pigmentation, physiologic pigmentation, addison's disease, melanotic macule, pigmented nevi, spitz nevus, post-inflammatory melanosis, hemochromatosis, oral melanoma, McCune-Albright syndrome and Peutz-Jegher's syndrome.[1718] In early stages, oral melanoma may be indistinguishable from other pigmented lesions. Therefore, sudden onset of oral pigmentation of unknown etiology needs histopathologic assessment for lesional identity and to rule out the presence of oral melanoma. The lesion may undergo spontaneous regression after incisional biopsy. The present case required surgical excision only as a treatment option since the clinical presentation was diffuse gingival enlargement interfering with normal mastication.

CONCLUSION

To the best of our knowledge, this is the first case of gingival melanoacanthoma in the Indian sub-continent. Pigmented gingival lesions of unusual clinical presentation should undergo histopathologic examination for timely identification and to rule out malignancy. Our case report emphasizes the need for clinicians to include gingival melanoacanthoma in the differential diagnosis of multifocal diffuse pigmented gingival enlargement and surgical excision is only treatment modality for such unusual clinical presentation.