Publish date: Posted on
Last updated: January 4, 2024
Keywords #
lentigo maligna
lentigo maligna melanoma
melanoma
moles
nevi
pigmented lesions
Diagnosis #
Melanoma is a skin cancer that occurs as a result of malignant transformation of melanocytes, the pigment-producing cells of the epidermis. Melanoma most often develops de novo, not from a preexisting mole. 28% of the time, melanoma arises from a preexisting mole.[1] The main subtypes of melanoma include superficial spreading melanoma, acral lentiginous melanoma, nodular melanoma, and lentigo maligna melanoma. Risk factors for melanoma include exposure to ultraviolet radiation or indoor tanning bed use, personal history of melanoma, family history of melanoma, and personal traits such as: red or blonde hair, blue eye color, numerous or clinically atypical nevi, history of atypical nevi, and fair skin complexion.[2]
Key Concepts #
- Melanoma represents a malignant transformation of melanocytes.
- Melanoma typically develops de novo rather than within a preexisting nevus.
- Common methods used to identify melanoma are the ABCDE checklist, dermoscopy, and the “ugly duckling” sign.
- Lesions suspicious for melanoma should undergo excisional biopsy. Shave biopsy is acceptable if at least 1-2mm of depth and the entire clinical lesion (i.e. pigmented component) is removed.
- Definitive diagnosis of melanoma is based on histological features.
- Prognosis is based on tumor thickness.
Epidemiology #
In the United States, melanoma is the fifth most common malignancy in men and the sixth most common in women.[3] Each year in the United States, nearly 80,000 cases of invasive melanoma are diagnosed and over 9,000 deaths are attributed to melanoma. Incidence rates of melanoma increased by 1.8% each year on average from 2003-2016 with the largest increase occurring in non-Hispanic whites.[4] Approximately 5-10% of melanoma patients have a positive family history.[5]
Clinical Features #
- A common method used to identify melanoma on visual inspection is the ABCDE checklist.
- Concern for melanoma is raised when a pigmented lesion demonstrates: A) asymmetry, B) border irregularity, C) color variegation, D) diameter > 6 mm, E) evolution or change.
- Another feature used for visual inspection is the “ugly duckling” sign, which is positive when a single lesion stands apart from a patient’s signature or most common-appearing nevi.
- Dermoscopic features are blue-white veil, fine white crystalline structures, polymorphous vessels, eccentric blotch, radial streaming.
- Increased Breslow depth, determined histopathologically, and ulceration are poor prognostic factors that increase risk of metastasis and death.
Differential Diagnoses #
- Atypical nevus
- Seborrheic keratosis
- Solar lentigos
- Pigmented basal cell carcinoma
- Spitz nevus
- Thrombosed hemangioma/angiokeratoma
Diagnostic Workup #
Any pigmented lesion suspicious for melanoma must undergo an excisional biopsy or deep shave removal (at least 2 mm depth). The entire visible pigmented component of the lesion must be removed by biopsy to avoid sampling error. Highly suspicious lesions should undergo full-thickness excision with 1- to 3-mm margins preferred.[6] Definitive diagnosis of melanoma is based on histology. Lesions will often demonstrate atypical melanocytes, asymmetry, spread of melanocytes into the epidermis (pagetoid scatter), and host lymphocytic response. Immunohistochemistry can also be helpful using markers such as SOX-10 and Melan-A. The strongest prognostic factor for melanoma is the tumor thickness, or Breslow depth. This measurement is taken by measuring the distance in millimeters from the granular layer of the epidermis to the deepest malignant cell. Breslow depth can be used to guide clinical decisions such as excision margins and sentinel lymph node biopsy.[6]
Treatment #
The initial treatment for melanoma is surgical resection of the primary tumor. However, for more advanced stages of melanoma, sentinel lymph node biopsy is performed with the wide local excision, and may be followed by systemic adjuvant therapy. Additional local treatment options include topical imiquimod (for lentigo maligna), radiation therapy, or intralesional injections, whereas regional therapy consists of either isolated limb infusion or perfusion.[6] Systemic regimens traditionally included immunotherapy with interferon-alpha, but recently immune checkpoint inhibitors, such as ipilimumab and nivolumab, and selective inhibitors of the MAPK pathway, such as dabrafenib and trametinib, are now FDA-approved.[7]
Slide Viewer #
https://utahderm.med.utah.edu/image-viewer/References #
- Lin WM, Luo S, Muzikansky A, et al. Outcome of patients with de novo versus nevus-associated melanoma. J Am Acad Dermatol. 2015;72(1):54-58. doi:10.1016/j.jaad.2014.09.028
- Gandini S, Sera F, Cattaruzza MS, et al. Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi. Eur J Cancer. 2005;41(1):28-44. doi:10.1016/j.ejca.2004.10.015
- Siegel RL, Miller KD, Fedewa SA, et al. Cancer statistics, 2017. CA Cancer J Clin. 2017;67:7-30. doi:10.3322/caac.21395
- Melanoma Incidence and Mortality, United States–2012-2016. US Cancer Stat Data Br. 9.
- Leachman SA, Carucci J, Kohlmann W, et al. Selection criteria for genetic assessment of patients with familial melanoma. J Am Acad Dermatol. 2009. doi:10.1016/j.jaad.2009.03.016
- Coit DG, Thompson JA, Albertini MR, et al. Cutaneous Melanoma, Version 2.2019, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Cancer Netw. 2019. doi:10.6004/jnccn.2019.0018
- Long G V., Stroyakovskiy D, Gogas H, et al. Combined BRAF and MEK inhibition versus BRAF inhibition alone in melanoma. N Engl J Med. 2014;371(20):1877-1888. doi:10.1056/NEJMoa1406037
