Melanoma classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:  Yazan Daaboul, M.D.; Serge Korjian M.D.

## Overview[edit | edit source]

Melanoma may be classified into either cutaneous or non-cutaneous melanomas. The most common 4 sub-types of cutaneous melanoma include superficial spreading melanoma, nodular melanoma, acral lentiginous melanoma, and lentigo maligna melanoma. Less common sub-types of melanoma include desmoplastic/spindle cell melanoma, nevoid melanoma, spitzoid melanocytic melanoma, angiotropic melanoma, blue nevus-like melanoma, and composite melanoma.

## Classification of Melanoma[edit | edit source]

Shown below is a table that demonstrates the various sub-classes of melanoma:[1][2]

Subtype | Frequency | Clinical Features

|
|

Common Subtypes
Superficial spreading melanoma | 70% |

* Most common sub-type
* Usually affects sun exposed sites among both men and women aged 50-70 years
* Characterized by the presence of abundant junctional intra-epidermal spread of malignant melanocytes

Nodular melanoma | 15-25% |

* Second most common subtype
* Usually affects sun exposed sites among both men and women aged 50-70 years
* Characterized by the absence of junctional intra-epidermal spread of malignant melanocytes

Acral lentiginous melanoma | 5% |

* Not associated with chronic ultraviolet exposure
* Affects the extremities of individuals of all races
* Common among the elderly Caucasian and non-Caucasian individuals

Lentigo maligna melanoma | 1-5% |

* Preceded by lentigo maligna
* Common among the elderly Caucasian patients
* Usually appears as a flat, non-palpable lesion that affects sun exposed sites, especially the head and neck (lesions on extremities are less common)

Non-cutaneous melanoma | 5% |

* Melanoma that does not affect the skin
* Usually affects the eye (ocular melanoma) or the mucus membranes (mucosal melanoma)

Less Common Subtypes
Desmoplastic/Spindle cell melanoma | Rare |

* Lesion typically amelanotic and has a morphology similar to a scar tissue
* Appears indolent but is highly infiltrative
* Characterized by local recurrence and perineural spread
* Usually affects males aged 60-70 years in sun exposed sites
* May be de novo or can be associated with a pre-existing melanoma
* Has several subtypes:

* Pure: paucicellular
* Desmoplastic-neurotropic melanoma: characterized by neurotropism
* Pure neurotropic melanoma: no desmoplasia with spindle cell melanoma of neurotropic phenotype
* Mixed/Combined: epithelial and spindle cells

Nevoid melanoma | Rare |

* Lesion has features of both melanoma and melanocytic nevus on histopathological analysis
* Clinical features resemble those of a typical melanoma

Spitzoid melanocytic neoplasm | Rare |

* Lesion has features of both melanoma and Spitz (epithelioid) tumor
* Typically affects sun exposed sites among children and young adults, but adults with Spitz tumors are more often diagnosed with Spitzoid melanoma
* Compared to benign Spitz tumors, Spitzoid melanomas are usually large (>5 mm)

Angiotropic melanoma | Rare |

* Lesion characterized by angiotropism, whereby the melanoma grows in proximity (within 1-2 mm) to blood and/or lymphatic tissue but no tumor within the vascular lamina itself
* The tumor may originally be another sub-type of melanoma
* Clinical features similar to typical melanoma

Blue nevus-like melanoma | Rare |

* Melanoma that develops from a pre-existing blue nevus
* One of the rarest forms of melanoma
* Appears as a blue nevus that has recently been rapidly expanding with irregular contours
* Typically affects middle-aged men

Composite melanoma | Rare |

* Melanoma that develops in the proximity of other pre-existing epithelial malignancies (e.g. basal/squamous cell carcinoma)
* May be characterized by one of the following:

* Collision tumor: Collision of melanoma and another nearby malignant tumor
* Colonization: Colonization of melanocytes in a tumor
* Combined: Two distinct tumors appear to have mixed features of the melanoma and the other tumor
* Biphenotypic: One tumor that has features of melanoma and another epithelial malignancy

## References[edit | edit source]

1. ↑ Schanderdorf D, Kochs C, Livingstone E (2013). Handbook of Cutaneous Melanoma: A Guide to Diagnosis and Treatment. Springer.CS1 maint: Multiple names: authors list (link)
2. ↑ Mooi W, Krausz T (2007). Pathology of Melanocytic Disorders 2nd Ed. CRC Press.

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