Skin melanocytic tumor
Nevi
Dysplastic nevus
Author: Christopher S. Hale, M.D.
Topic Completed: 1 September 2014
Minor changes: 3 November 2020
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: Dysplastic nevus
Table of Contents
Definition / general | Terminology | Epidemiology | Clinical features | Case reports | Treatment | Dermoscopy | Dermoscopic images | Clinical images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Molecular / cytogenetics description | Electron microscopy description | Differential diagnosisCite this page: Hale CS. Dysplastic nevus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skintumormelanocyticdysplasticnevus.html. Accessed March 4th, 2021.
Definition / general
- Controversial topic, particularly for solitary lesions; better defined in dysplastic nevus syndrome (multiple dysplastic nevi and two family members with melanoma, J Am Acad Dermatol 2012;67:1.e1, eMedicine: Atypical Mole (Dysplastic Nevus))
Terminology
- Also called atypical nevus, nevus with architectural disorder, nevus with architectural disorder and cytologic atypia, Clark nevus
Epidemiology
- Develop in teenager years and into adulthood
- Atypical nevi of scalp of adolescents resemble those in genitalia with apparent benign behavior (J Cutan Pathol 2007;34:365)
- May be intermediate step in pathway between benign nevus and melanoma (J Clin Pathol 2005;58:453)
- Relative risk of 46x for melanoma in one study of Dutch patients with 5+ atypical nevi (J Am Acad Dermatol 2007;56:748)
- Higher risk for melanoma with more severe atypia (Mod Pathol 2003;16:764)
- May occasionally be associated with neurofibroma (J Cutan Pathol 2007;34:837)
Clinical features
- Atypical due to size > 5 mm, irregular borders and variegated appearance
Case reports
- 22 year old man with multiple eruptive dysplastic nevi and post-chemotherapy in situ melanomas (Pediatr Dermatol 2007;24:135)
- 24 year old man with pointillist dysplastic nevus (Arch Dermatol 2005;141:763)
- 44 year old man with agminated dysplastic nevi and atypical mole syndrome (Arch Dermatol 2001;137:917)
- 49 year old and 55 year old women with melanoma and intradermal sebocyte-like melanocytes in nevi (Am J Dermatopathol 2007;29:566)
Treatment
- Initial diagnostic biopsy should sample entire lesion (Australas J Dermatol 2005;46:70)
- Mildly atypical nevi are considered benign and no additional treatment is necessary
- Severely atypical nevi are excised with negative margins
- No consensus on moderate atypia; most physicians re-excise if possible if margins are positive
Dermoscopy
- Pigment patterning often disrupted with brown dots, frequently erratically placed
- Nevi often irregular in shape, asymmetric, with variable coloration and borders that vary from sharply to poorly defined
Dermoscopic images
Images hosted on other servers:
Dysplastic
pointillist
nevi with multiple
brown dots
"Diffuse and patchy" network pattern
Clinical images
Images hosted on other servers:
Agminated atypical nevi
Agminated atypical nevi on right arm
Multiple melanocytic nevi (anterior chest and abdomen)
Various images
Minimal change in a clinically dysplastic nevus
Evolving and regressing clinical dysplastic nevus
Development of a clinically dysplastic nevus
Microscopic (histologic) description
- Compound nevi with marked lentiginous proliferation of melanocytes at dermoepidermal junction, extending at least 3 rete ridges beyond lateral margins of dermal component
- Nests have cytologic and architectural atypia, including irregular sizes and shapes and bridging of adjacent rete ridges, which are irregular themselves
- Papillary dermal lamellar fibroplasia with perivascular infiltrate and vascular dilation
- Usually mild / moderate cytologic atypia (nuclear hyperchromasia, prominent nucleoli, dusty melanin pigment)
- Melanocytes are spindled and parallel to surface or epithelioid
- Epidermolytic hyperkeratosis present but not specific (Am J Dermatopathol 2002;24:23)
- Mild atypia:
- At high power, nuclei of melanocytes are condensed, oval / ellipsoid, hyperchromatic, indented and have no / small nucleoli
- Perinuclear halo common; no / minimal pagetoid upward migration of melanocytes
- No mitotic figures in dermal component
- Moderate atypia:
- At high power, nevus nuclei are variable in size and chromatin, although some have "mild atypia" plus small nucleoli
- Enlarged cytoplasm compared to melanocyte, no halo
- Few but normal mitotic figures in upper dermal part of nevus
- Severe atypia:
- Usually asymmetrical, but still well-circumscribed in epidermis
- Usually nests of nevus cells, not individual cells
- Some central upward migration of individual nevus cells
- Crowded nests in dermis
- Enlarged nuclei, often bizarre hyperchromatic nuclei mixed with small nuclei and prominent nucleoli
- No confluent atypia as seen with melanoma; frequent mitoses in junctional component, but not in deep dermal component
- Note: grading is not consistent between pathologists (Br J Dermatol 2006;155:988)
- Children:
- May want to downgrade atypia since ordinary childhood nevi have large nests and large nevus cell size, as well as focal atypia
- Pagetoid upward migration at periphery:
- May suggest upgrading to melanoma in situ
- Mitotic figures at base of dermal component::
- Suggests invasive melanoma
Microscopic (histologic) images
AFIP images
Clark nevus
Contributed by Aleodar Andea, M.D.
Dysplastic nevus
Contributed by Asmaa Gaber Abdou, M.D.
Various images
Images hosted on other servers:
Dysplastic nevus
Pointillist dysplastic nevus with cytologic atypia
Strong BRMS1 (A); weak Cul1 (B)
Lentiginous melanocytic
proliferation with
papillary dermal
fibrosis
Positive stains
- Ki67 index intermediate between benign nevi and melanoma (Appl Immunohistochem Mol Morphol 2007;15:160)
- Immunostains for TSLC1 may help distinguish dysplastic nevi from melanoma (Melanoma Res 2012;22:430)
Molecular / cytogenetics description
- Usually diploid
- Often mutations in CDKN2A (Cancer 2002;94:3192)
- 24% have high risk mucosal HPV by PCR (Br J Dermatol 2005;152:909)
- Microarray analysis of four markers (ING4, Cul1, BRG1 and Bim) may distinguish melanoma from dysplastic nevi (PLoS One 2012;7:e45037)
Electron microscopy description
- Cases with severe dysplasia share several features with radial growth phase melanomas, including large cell size, bizarre shaped and pleomorphic nuclei, well developed Golgi, abundant and deranged mitochondria, aberrant melanosomes with deranged structures and irregular melanization
Differential diagnosis
- Common nevus with some dysplastic features (Am J Dermatopathol 2000;22:391)
- In situ melanoma arising in a compound nevus: atypia limited to epidermis, consumption of epidermis present (Am J Dermatopathol 2007;29:527), be cautious if partial excision (J Cutan Pathol 2005;32:405)
