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AUTHOR AND EDITOR INFORMATION

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Author: Talib Najjar, DMD, MDS, PhD, Professor of Oral and Maxillofacial Surgery and Pathology, University of Medicine and Dentistry of New Jersey

Coauthor(s): Thomas A Chiodo, DDS, Staff Dentist, Department of Oral and Maxillofacial Surgery, University of Medicine and Dentistry of New Jersey; Private Practice, Oral and Maxillofacial Surgery; Nathan Wuebbels, DMD, MD, Staff Physician, Department of Oral and Maxillofacial Surgery, University of Medicine and Dentistry, New Jersey, University Hospital

Editors: Neil Shear, MD, Professor and Chief of Dermatology, Professor of Medicine, Pediatrics and Pharmacology, University of Toronto Faculty of Medicine; Head of Dermatology, Sunnybrook Women's College Health Sciences Center and Women's College Hospital, Canada; Michael J Wells, MD, Associate Professor, Department of Dermatology, Texas Tech University Health Sciences Center; Jeffrey J Miller, MD, Associate Professor, Department of Dermatology, Penn State University, Milton S Hershey Medical Center; Glen H Crawford, MD, Assistant Clinical Professor, Department of Dermatology, University of Pennsylvania School of Medicine; Chief, Division of Dermatology, The Pennsylvania Hospital; Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center

Author and Editor Disclosure

Synonyms and related keywords: oral melanoacanthoma, melanoacanthoma, mucosal melanoacanthoma, mucosal lesions, cutaneous melanoacanthoma, pigmented seborrheic keratosis, melanocyte and keratinocyte proliferation, pigmented macular lesions, benign nonovoid melanoepithelioma

INTRODUCTION

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Background

Melanoacanthoma is a rare condition of oral mucosa  that has been reported only in the last century. The lesion is characterized by a proliferation of both melanocytes and keratinocytes that results in pigmented macular or plaquelike lesions (see Media File 1).

Oral melanoacanthoma is regarded by many as a reactive condition unrelated to cutaneous melanoacanthoma, but the histologic features are similar. Cutaneous and mucosal melanoacanthoma differ in terms of patient age, patient race, and site.

In 1927, Bloch provided the earliest known description of melanoacanthoma, which was reported in the German literature.1 Bloch described several skin lesions, which he originally called benign nonovoid melanoepithelioma of the skin. He further subdivided his cases into 2 types: In the histologic samples studied, type 1 had both dendritic melanocytes and keratinocytes, whereas the histologic appearance of type 2 was similar to that of type 1, but it lacked the dendritic melanocytes.

In 1960, Mishima and Pinkus reexamined the condition and further refined the diagnostic terminology.2 The condition that Bloch designated as type 1 is currently called melanoacanthoma, and type 2 is currently called pigmented seborrheic keratosis.

Although cutaneous lesions of melanoacanthoma were reported as early as 1927, Tomich et al at the American Academy of Oral Pathology first reported oral mucosal lesions in 1978.1 Although many authors subsequently published case reports, Goode et al published the first case report in 1983.3 This was a retrospective review of 10 cases of oral melanoacanthoma reported in the literature.

To date, oral melanoacanthoma remains a rare condition, with approximately fewer than 100 reported cases. The cutaneous variant is also rare; however, it is more prevalent than the mucosal variant.

Pathophysiology

The mucosal variants of melanoacanthoma have histologic appearances similar to that of cutaneous melanoacanthoma. The lesion consists of proliferating melanocytes and keratinocytes, which result in large pigment-containing dendritic cells. The dendritic cells are present throughout the middle and upper layers of the epithelium.

Inflammation occurs almost universally in patients with mucosal lesions. The presence of inflammation and the spontaneous resolution of oral lesions are suggestive of a reactive process rather than a neoplastic process. The observation of trauma and inflammation associated with oral lesions has led to the conclusion that the mucosal variant is likely the result of a reactive process rather than a neoplastic process.4

Frequency

United States

Oral melanoacanthoma is rare, with only approximately fewer than 100 cases reported since 1978,5, 6, 7 when the lesions were first reported. The cutaneous variant is more common, but it is still relatively rare among skin lesions. Among all the cases reported, specific patterns are described with respect to the race, sex, and age of patients with cutaneous melanoacanthomas and those with mucosal melanoacanthomas.

Race

  • Cutaneous lesions of melanoacanthoma are reported almost exclusively in white patients.
  • The mucosal variant is reported almost exclusively in black patients.8, 9
  • Some sporadic mucosal cases are reported in Asian individuals.

Sex

The prevalence for both variants of melanoacanthoma is fairly equal in both sexes, with a slight female predominance.10 The female-to-male ratio is approximately 3:2.

Age

The age distributions of the 2 types of melanoacanthoma differ.11

  • Cutaneous lesions are found in patients with a mean age of approximately 60 years.
  • Mucosal lesions appear in patients with a mean age of approximately 25 years.


CLINICAL

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History

Because the lesions of oral melanoacanthoma are not painful, physicians usually discover them on routine oral examination.

Physical

The clinical features of oral melanoacanthoma may mimic those of other pigmented lesions. For example, the clinical and histologic features of oral melanoacanthoma lesions can resemble those of melanoma in situ.

  • Cutaneous lesions
    • Cutaneous lesions are reported in the scalp, eyelid, ear, nose, neck, thorax, and abdomen.
    • Cutaneous lesions may be found on any area of the head and neck, as well as on the chest, abdomen, back, or legs.
    • The lesions are generally asymptomatic, flat or slightly raised hyperpigmented areas.
    • The color of the lesions ranges from brown to black to blue.
    • Lesions are usually isolated, with no apparent precipitating factors.
    • Lesions are slow growing and are usually present for months before treatment is sought.
  • Mucosal lesions
    • Mucosal lesions can occur in the buccal mucosa, labial mucosa, palate, gingiva (see Media File 2),12 alveolar ridge, or lip.13, 14
    • Although the appearance of mucosal lesions is similar to that of cutaneous lesions, mucosal lesions have a more rapid onset and rate of growth.15
    • Mucosal lesions occur mostly on the lip, buccal mucosa,16 or palate,17 and they are precipitated by a traumatic event.
    • The diameter of the mucosal lesions can range from a few millimeters to several centimeters.

Causes

The role of trauma in the development of the lesion remains controversial, but any irritant must be removed.


DIFFERENTIALS

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Seborrheic Keratosis

Other Problems to be Considered

Melanoma in situ
Melanosis
Superficial melanoma
Junctional melanocytic nevus
Melanotic macule
Pigmented basal cell epithelioma


WORKUP

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Procedures

  • The clinical features of cutaneous and mucosal lesions may mimic those of other pigmented lesions; therefore, definitive diagnosis is based on histologic examination.
  • Incisional or excisional biopsy may be performed based on the size and the anatomic location of the lesion.

Histologic Findings

Microscopic examination reveals a hyperplastic edematous stratified squamous epithelium with acanthosis and elongated widened rete ridges. Increased melanin pigmentation is present in the basal layer (see Media File 3). In addition, many proliferating dendritic melanocytes or clear cells extend upward into the prickle-cell layers (see Media File 4).

The clinical and histologic features of oral melanoacanthoma lesions can resemble those of melanoma in situ.18 Usually, no evidence of cellular pleomorphism or abnormal mitotic activity is seen in oral melanoacanthomas, and this feature excludes malignancy.

In mucosal lesions, mixed chronic inflammatory cells and numerous melanin-laden macrophages densely infiltrate the stratum corneum. This inflammatory process may indicate the reactive rather than the neoplastic nature of the lesion.19, 20


TREATMENT

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Medical Care

No medical treatment for mucosal or cutaneous lesions is known. A low risk of recurrence exists.

  • In patients with mucosal lesions, treatment may be limited to the removal of the precipitating stimulus.21
  • Lesions spontaneously resolve in approximately 40% of patients with oral lesions.2

Surgical Care

Surgical excision is the treatment of choice for both mucosal and cutaneous lesions.

  • Because rare cases of premalignant or malignant cutaneous lesions are reported, wider resection with clear margins is recommended.
  • In benign cutaneous melanoacanthoma, local excision or ablation of the site is adequate.
  • If mucosal lesions do not resolve, local excision or ablation is indicated.
  • Cryosurgery, electrosurgery, or laser treatment22 may be used to remove lesions; however, these modalities may jeopardize the microscopic diagnosis.
  • The Medscape Dermatologic Surgery Resource Center may be helpful.


FOLLOW-UP

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Complications

  • No evidence of malignant transformation has been reported.
  • No complications arise from incisional or excisional biopsy.

Prognosis

  • Initially, cutaneous lesions were suspected to be malignant, and subsequently, the lesions were linked to a transformation to low-grade malignancy.
    • Malignant transformation has been reported in at least 2 cases.
    • However, most lesions are considered benign and should be treated conservatively.
  • No cases of recurrence or metastasis have been reported in either the mucosal variant or cutaneous variant.
  • A low risk of recurrence exists.
  • To date no malignant oral melanoacanthoma have been reported.


MISCELLANEOUS

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Medical/Legal Pitfalls

  • Melanoacanthoma is a benign lesion with little legal impact; however, the clinical and morphologic differential diagnosis is essential to rule out malignant melanoma.23 Melanoma is a fatal lesion with clear medical and legal consequences.


MULTIMEDIA

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Media file 1:  Diagram of a pigmented epithelial macule.
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Media type:  Image

Media file 2:  Intraoral melanoacanthoma lesion on the mandibular gingiva.
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Media type:  Photo

Media file 3:  Increased melanin pigmentation in the basal layer of a melanoacanthoma (hematoxylin and eosin, original magnification X10).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo

Media file 4:  Proliferating dendritic melanocytes in the prickle-cell layers of a melanoacanthoma (hematoxylin and eosin, original magnification X40).
Click to see larger pictureClick to see detailView Full Size Image
Media type:  Photo


REFERENCES

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  1. Schneider LC, Mesa ML, Haber SM. Melanoacanthoma of the oral mucosa. Oral Surg Oral Med Oral Pathol. Sep 1981;52(3):284-7. [Medline].
  2. Wright JM, Binnie WH, Byrd DL, Dunsworth AR. Intraoral melanoacanthoma. J Periodontol. Feb 1983;54(2):107-11. [Medline].
  3. Goode RK, Crawford BE, Callihan MD, Neville BW. Oral melanoacanthoma. Review of the literature and report of ten cases. Oral Surg Oral Med Oral Pathol. Dec 1983;56(6):622-8. [Medline].
  4. Horlick HP, Walther RR, Zegarelli DJ, Silvers DN, Eliezri YD. Mucosal melanotic macule, reactive type: a simulation of melanoma. J Am Acad Dermatol. Nov 1988;19(5 Pt 1):786-91. [Medline].
  5. Contreras E, Carlos R. Oral melanoacanthosis (melanoachantoma): report of a case and review of the literature. Med Oral Patol Oral Cir Bucal. Jan-Feb 2005;10(1):11-2; 9-11. [Medline].
  6. Fornatora ML, Reich RF, Haber S, Solomon F, Freedman PD. Oral melanoacanthoma: a report of 10 cases, review of the literature, and immunohistochemical analysis for HMB-45 reactivity. Am J Dermatopathol. Feb 2003;25(1):12-5. [Medline].
  7. Frey VM, Lambert WC, Seldin RD, Schneider LC, Mesa ML. Intraoral melanoacanthoma. J Surg Oncol. Oct 1984;27(2):93-6. [Medline].
  8. Carlos-Bregni R, Contreras E, Netto AC, Mosqueda-Taylor A, Vargas PA, Jorge J, et al. Oral melanoacanthoma and oral melanotic macule: a report of 8 cases, review of the literature, and immunohistochemical analysis. Med Oral Patol Oral Cir Bucal. Sep 1 2007;12(5):E374-9. [Medline].
  9. Tomich CE, Zunt SL. Melanoacanthosis (melanoacanthoma) of the oral mucosa. J Dermatol Surg Oncol. Mar 1990;16(3):231-6. [Medline].
  10. Yarom N, Hirshberg A, Buchner A. Solitary and multifocal oral melanoacanthoma. Int J Dermatol. Dec 2007;46(12):1232-6. [Medline].
  11. Chandler K, Chaudhry Z, Kumar N, Barrett AW, Porter SR. Melanocanthoma: a rare cause of oral hyperpigmentation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. Nov 1997;84(5):492-4. [Medline].
  12. Flaitz CM. Oral melanoacanthoma of the attached gingiva. Am J Dent. Jun 2000;13(3):162. [Medline].
  13. Matsuoka LY, Glasser S, Barsky S. Melanoacanthoma of the lip. Arch Dermatol. Sep 1979;115(9):1116-7. [Medline].
  14. Sexton FM, Maize JC. Melanotic macules and melanoacanthomas of the lip. A comparative study with census of the basal melanocyte population. Am J Dermatopathol. Oct 1987;9(5):438-44. [Medline].
  15. Whitt JC, Jennings DR, Arendt DM, Vinton JR. Rapidly expanding pigmented lesion of the buccal mucosa. J Am Dent Assoc. Oct 1988;117(5):620-2. [Medline].
  16. Fatahzadeh M, Sirois DA. Multiple intraoral melanoacanthomas: a case report with unusual findings. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. Jul 2002;94(1):54-6. [Medline].
  17. Buchner A, Merrell PW, Carpenter WM. Relative frequency of solitary melanocytic lesions of the oral mucosa. J Oral Pathol Med. Oct 2004;33(9):550-7. [Medline].
  18. Lambert WC, Lambert MW, Mesa ML, Schnieder LC, Fischman GJ, Abbey AH, et al. Melanoacanthoma and related disorders. Simulants of acral-lentiginous (P-P-S-M) melanoma. Int J Dermatol. Oct 1987;26(8):508-10. [Medline].
  19. Wright JM. Intraoral melanoacanthoma: a reactive melanocytic hyperplasia. Case report. J Periodontol. Jan 1988;59(1):53-5. [Medline].
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Oral Melanoacanthoma excerpt

Article Last Updated: Oct 6, 2008