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Dermatology > BENIGN NEOPLASMS
Cutaneous Melanoacanthoma
Article Last Updated: May 16, 2008
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Robert A Schwartz is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and Sigma Xi
Coauthor(s):
W Clark Lambert, MD, PhD, Professor and Head, Dermatopathology, Departments of Pathology and Dermatology, UMDNJ-New Jersey Medical School;
George G Kihiczak, MD, Resident, Department of Dermatology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey
Editors: Michelle Pelle, MD, Clinical Assistant Professor, Division of Dermatology, Department of Medicine, University of California at San Diego; David F Butler, MD, Professor of Dermatology, Texas A&M University College of Medicine; Director, Division of Dermatology, Scott and White Clinic; Director Dermatology Residency Training Program, Scott and White Clinic; Christen M Mowad, MD, Associate Professor, Department of Dermatology, Geisinger Medical Center; Catherine Quirk, MD, Clinical Assistant Professor, Department of Dermatology, Brown University; Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Author and Editor Disclosure
Synonyms and related keywords:
benign mixed tumor of melanocytes and malpighian cells, seborrheic keratoses, melanoepithelioma type I, melanoepithelioma type II, keratinocytes, dendritic melanocytes, MA, oral melanoacanthoma
Background
Melanoacanthoma is a term that Mishima and Pinkus1 introduced in 1960 to describe a pigmented, benign proliferation of both keratinocytes and dendritic melanocytes. Prior to this designation, Bloch2 described a similar lesion in 1927 that he called melanoepithelioma type I. Melanoepithelioma type II is an ordinary pigmented seborrheic keratosis. Oral melanoacanthoma is a rare, reactive, mucosal lesion, which, similar to cutaneous melanoacanthoma, is associated with hyperplasia of spinous keratinocytes and melanocytes.3 Its most common intraoral sites are the buccal mucosa, lip, palate, and gingiva. The average age at presentation is 28 years, and it occurs mainly in blacks, with a strong female predilection.4 Oral melanoacanthoma is unrelated to seborrheic keratosis. Oral melanoacanthoma is most often seen as an enlarging flat or slightly raised area of hyperpigmentation on the buccal mucosa of adult black women. Strong homatropine methylbromide reactivity has been described, limiting its utility in distinguishing oral melanoacanthoma from malignant melanoma.
The eMedicine article Oral Melanoacanthoma may be of interest, as may the Medscape Dermatologic Surgery Resource Center.
Pathophysiology
Although melanoacanthoma can be found both on the skin and oral mucosa, the focus of this review is cutaneous melanoacanthoma. Although most authors consider cutaneous melanoacanthoma a benign tumor of melanocytes and keratinocytes, some have suggested it may be a reactive phenomenon induced by localized trauma.5
Frequency
United States
Cutaneous melanoacanthoma is generally regarded as rare. It was the primary diagnosis in 5 of 500,000 consecutive skin biopsy samples in one series from the United States.6
International
In their series of 189 consecutive seborrheic keratoses diagnosed among Spanish patients, Simon et al7 found that cutaneous melanoacanthoma represented 28% of all seborrheic keratoses.
Mortality/Morbidity
- Cutaneous melanoacanthoma is a benign neoplasm. Simple excision is curative.
- Morbidity is uncommon. However, a melanoacanthoma that extends from the upper eyelid to beyond the lower eyelid can obstruct the patient's vision. The authors have observed this complication.
- Melanoacanthomas may be as large as 10 cm in diameter and can therefore be unappealing to the patient.
Race
Cutaneous melanoacanthoma is described more frequently white patients than in others. However, the lesion is rare in all ethnic groups.
Sex
Cutaneous melanoacanthoma develops in males and females with the same frequency.
Age
Cutaneous melanoacanthoma develops in middle-aged and elderly people. Melanoacanthoma has been described in patients aged 46-81 years, with an average age of 55-65 years.6, 8
History
- Cutaneous melanoacanthomas are painless and slow growing. Their slow but persistent growth and related cosmetic problems may prompt an affected individual to consult a physician.
- Patients are generally asymptomatic; however, trauma or manipulation of the lesions may lead to bleeding or inflammation.
- Patients may live with cutaneous melanoacanthoma for decades before they seek treatment.
Physical
- Melanoacanthomas are most often solitary.
- Multiple melanoacanthomas have been described.
- In one case, a 40-year-old man had multiple, minute, discrete or confluent shiny papules limited to his left upper eyelid.9
- Cutaneous melanoacanthomas are found mainly on the trunk or head, often on the lip or eyelid. They have also been observed on the penile shaft.8
- Cutaneous melanoacanthomas may be hyperpigmented or verrucous and round or oval.
- The lesion may be a papule, plaque, cutaneous horn, or nodule.
- Lesional diameters range from a few millimeters to 10 cm.
- The authors have observed a darkly pigmented cutaneous horn that extended from the left upper eyelid to below the lower eyelid in a 45-year-old man; the lesion had histologic findings consistent with melanoacanthoma (see Media File 1).
- Melanoacanthomas can occur on the oral mucosa, but oral lesions are distinct from cutaneous melanoacanthomas. The oral melanotic macule is a small, well-circumscribed, brown-to-black macule that occurs on the lips and mucous membranes.4
Causes
- The cause of melanoacanthoma is unknown, but most instances appear to represent a benign neoplasm.
- Irritation or trauma to the skin may cause some cutaneous melanoacanthomas, especially on the lips.
- Trauma and irritation of the oral mucosa are believed to cause oral melanoacanthoma.
Actinic Keratosis
Cutaneous Horn
Epidermal Nevus Syndrome
Malignant Melanoma
Postinflammatory Hyperpigmentation
Seborrheic Keratosis
Warts, Nongenital
Other Problems to be Considered
Melanotic macule
Pigmented melanocytic nevus
Pigmented malignant hidroacanthoma simplex10
Lab Studies
- Laboratory studies are not required.
Imaging Studies
- Imaging studies are not required.
Procedures
- Simple shave biopsy or excision, depending on the site of the melanoacanthoma, may be performed for diagnostic purposes.
- Because the lesions are epidermal and superficial, excision of the dermis and subcutis underlying a melanoacanthoma is not required or recommended.
Histologic Findings
Microscopic examination of cutaneous melanoacanthoma reveals a benign acanthoma composed of keratinocytes and dendritic melanocytes. Acanthosis, hyperkeratosis, parakeratosis, papillomatosis, and small horn pearls may be seen. Large dendritic melanocytes with abundant melanin granules are spread throughout the lesion. Cytologic atypia is not a feature of the melanocytes or keratinocytes in a melanoacanthoma. Two types of melanoacanthomas are described: a diffuse type in which melanocytes are unevenly scattered throughout the lesion and a clonal type in which melanocytes and keratinocytes are clustered in small nests.6 Electron microscopic studies reveal that the transfer of melanin from these highly dendritic melanocytes to neighboring keratinocytes is either partially or, in some cases, completely disrupted.11 Immunoprecipitation assays and immunofluorescent studies show that melanoacanthoma is unrelated to malignant melanoma.
Surgical Care
- Simple excision is curative.
- One theory suggests that cutaneous melanoacanthoma may be self-limited and it resolves without intervention.
- Cutaneous melanoacanthoma is benign and may be removed with curettage.
- Cryotherapy may be used if the diagnosis is certain and if histologic examination is not required.
- Argon plasma coagulation is a new treatment option for oral melanoacanthoma.12
Consultations
A dermatologist should be consulted to confirm this diagnosis.
Pharmacologic therapies are not available.
Further Outpatient Care
- Standard follow-up care may be needed to assess healing and address cosmetic issues.
Complications
- Scarring can be expected after the surgical or cryotherapeutic removal of a melanoacanthoma.
- Melanoacanthomas that extend from the upper eyelid to beyond the lower eyelid can obstruct the patient's vision.
Prognosis
- Melanoacanthoma is benign.
- Removal of cutaneous melanoacanthoma is curative.
Patient Education
- Patients should be informed that cutaneous melanoacanthoma is benign and has no potential for malignant transformation.
- Cutaneous melanoacanthoma is not associated with any skin or visceral cancer; it is not an indicator of cancer, and its presence is not a risk factor for cancer.
Medical/Legal Pitfalls
- Melanoacanthoma should not be confused with melanoma, because the latter is a life-threatening cutaneous malignancy.
| Media file 1:
Large cutaneous melanoacanthoma in a 45-year-old man that obstructs his vision. |
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Media type: Photo
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| Media file 2:
Photomicrograph of cutaneous melanoacanthoma. Large polydendritic melanocytes are seen at all levels of the epidermis. Acanthosis, hyperkeratosis, and slight papillomatosis are also present (hematoxylin and eosin stain, original magnification X139). |
 | View Full Size Image | |
Media type: Photo
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- Mishima Y, Pinkus H. Benign mixed tumor of melanocytes and malpighian cells. Melanoacanthoma: Its relationship to Bloch's benign non-nevoid melanoepithelioma. Arch Dermatol. Apr 1960;81:539-50. [Medline].
- Bloch B. Uber benigne, nicht naevoide Melanoepitheliome der Haut nebst Bemerkungen uber das Wesen und die Genese der Dendritenzellen. Arch Dermatol Syph (Berlin). 1927;153:20-40.
- 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].
- 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].
- Matsuoka LY, Barsky S, Glasser S. Melanoacanthoma of the lip. Arch Dermatol. May 1982;118(5):290. [Medline].
- Prince C, Mehregan AH, Hashimoto K, Plotnick H. Large melanoacanthomas: a report of five cases. J Cutan Pathol. Aug 1984;11(4):309-17. [Medline].
- Simon P, Requena L, Sanchez Yus E. How rare is melanoacanthoma?. Arch Dermatol. Apr 1991;127(4):583-4. [Medline].
- Vion B, Mérot Y. Melanoacanthoma of the penis shaft. Report of a case. Dermatologica. 1989;179(2):87-9. [Medline].
- Spott DA, Heaton CL, Wood MG. Melanoacanthoma of the eyelid. Arch Dermatol. Jun 1972;105(6):898-9. [Medline].
- Lee JY, Lin MH. Pigmented malignant hidroacanthoma simplex mimicking irritated seborrheic keratosis. J Cutan Pathol. Oct 2006;33(10):705-8. [Medline].
- Schlappner OL, Rowden G, Philips TM, Rahim Z. Melanoacanthoma. Ultrastructural and immunological studies. J Cutan Pathol. Jun 1978;5(3):127-41. [Medline].
- Andrews BT, Trask DK. Oral melanoacanthoma: a case report, a review of the literature, and a new treatment option. Ann Otol Rhinol Laryngol. Sep 2005;114(9):677-80. [Medline].
- Delacretaz J. [Melanoacanthoma (author's transl)]. Dermatologica. 1975;151(4):236-40. [Medline].
- Flaitz CM. Oral melanoacanthoma of the attached gingiva. Am J Dent. Jun 2000;13(3):162. [Medline].
- Frey VM, Lambert WC, Seldin RD, Schneider LC, Mesa ML. Intraoral melanoacanthoma. J Surg Oncol. Oct 1984;27(2):93-6. [Medline].
- Kihiczak GG, Centurion SA, Schwartz RA, Lambert WC. Giant cutaneous melanoacanthoma. Int J Dermatol. Dec 2004;43(12):936-7. [Medline].
- Lambert MW, Lambert WC, Schwartz RA, Mesa ML, Brodkin RH, Abbey AH, et al. Colonization of nonmelanocytic cutaneous lesions by dendritic melanocytic cells: a simulant of acral-lentiginous (palmar-plantar-subungual-mucosal) melanoma. J Surg Oncol. Jan 1985;28(1):12-8. [Medline].
- 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].
- Matsuoka LY, Glasser S, Barsky S. Melanoacanthoma of the lip. Arch Dermatol. Sep 1979;115(9):1116-7. [Medline].
- 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].
Cutaneous Melanoacanthoma excerpt Article Last Updated: May 16, 2008
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