Melanoma classification: Difference between revisions

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*Most common subtype
*Most common subtype
*Usually affects sun exposed sites among both men and women aged 50-70 years
*Usually affects sun exposed sites among both men and women aged 50-70 years
*Characterized by presence of abundant junctional intraepidermal spread of malignant melanocytes
*Characterized by ''presence'' of abundant junctional intraepidermal spread of malignant melanocytes
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|Nodular melanoma||15-25%||
|Nodular melanoma||15-25%||
*Second most common subtype
*Second most common subtype
*Usually affects sun exposed sites among both men and women aged 50-70 years
*Usually affects sun exposed sites among both men and women aged 50-70 years
*Characterized by absence of junctional intraepidermal spread of malignant melanocytes
*Characterized by ''absence'' of junctional intraepidermal spread of malignant melanocytes
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|Acral lentiginous melanoma||5%||
|Acral lentiginous melanoma||5%||
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*Preceded by lentigo maligna
*Preceded by lentigo maligna
*Common among elderly Caucasian patients
*Common among elderly Caucasian patients
*Usually appears as a flat, non-palpable lesion that affects sun exposed sites, especially the head and neck (extremities less common)
*Usually appears as a flat, non-palpable lesion that affects sun exposed sites, especially the head and neck (extremities are less common)
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| Non-cutaneous melanoma||5%||
| Non-cutaneous melanoma||5%||
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| Desmoplastic/Spindle cell melanoma||Rare||
| Desmoplastic/Spindle cell melanoma||Rare||
*Lesion typically amelanotic
*Lesion typically amelanotic and has a morphology similar to a scar tissue
*Appears indolent but is highly infiltrative  
*Appears indolent but is highly infiltrative  
*Characterized by local recurrence and perineural spread
*Characterized by local recurrence and perineural spread

Revision as of 05:46, 22 August 2015

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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

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

Classification of Melanoma

Shown below is a table that demonstrates that various subclasses of melanoma:[1][2]

Subtype Frequency Clinical Features
Common Subtypes
Superficial spreading melanoma 70%
  • Most common subtype
  • Usually affects sun exposed sites among both men and women aged 50-70 years
  • Characterized by presence of abundant junctional intraepidermal 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 absence of junctional intraepidermal spread of malignant melanocytes
Acral lentiginous melanoma 5%
  • Not associated with chronic ultraviolet exposure
  • Affects the extremities among inidividuals of all races
  • Common among elderly Caucasian and non-Causasian individuals
Lentigo maligna melanoma 1-5%
  • Preceded by lentigo maligna
  • Common among elderly Caucasian patients
  • Usually appears as a flat, non-palpable lesion that affects sun exposed sites, especially the head and neck (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 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 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 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 subtype 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
  • Appear 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 proximity to 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

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

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