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Pathology of Dysplastic Nevus  

(Atypical Nevus)  

Dr Sampurna Roy MD          


Pathology Quiz Case 85: Case history and images:

Dermatopathology Quiz Case 134

Diagnosis: Mildly Dysplastic Compound Melanocytic

Nevus (Atypical Nevus)





Dysplastic nevi are usually compound nevi with peripheral lentiginous and junctional activity and random cytological atypia in the epidermal component.

Dysplastic (atypical) nevus syndrome includes familial (originally known as B-K mole syndrome) and sporadic occurrence of multiple dysplastic nevi in an individual.  

Gross appearance:

Tumour is characterized by ABCDE 

[A: Asymmetry, B: Border Irregularity, C: Colour Variation, D: Diameter more than 4mm, E: Elevation.] 

1) These are usually more than 4mm in diameter.

2) Dysplastic nevi usually present as a macule with or without papular component. 

3) The border is usually irregular and fuzzy in appearance. (Differential Diagnosis - In melanoma, a well defined border is present.)

4) The lesion displays colour variegation. A mixture of tan, dark brown and pink areas are noted.

[A: Asymmetry , B: Border Irregularity, C: Colour Variation,  D: Diameter more than 4mm , E: Elevation.]

Salient Histological Features: (Usually a low-power diagnosis)

1) Lentiginous hyperplasia

2) Random cytological atypia

3) Stromal response.

4) Architectural atypia

Lentiginous and nested hyperplasia noted in dysplastic naevus is characterized by proliferation of melanocytes singly and in groups along the basal layer.

'Junctional nest disarray' refers to uneven distribution and pattern of junctional component. 

The rete ridges of the epidermis show hyperplasia and fusion of adjacent retes.

The narrow elongated spindle shaped melanocytes run horizontally  between the rete- ridges forming part of a bridge.

Random cytological atypia is characterized by occasional cells with hyperchromatic nuclei  and prominent nucleoli.

The atypia is usually graded into low grade and severe.

There is no universally accepted criteria for grading.

(Differential diagnosis :  In melanoma the atypia is often 'non-random' in that all the nuclei are abnormal with enlarged irregular nuclei).

The stromal response includes lamellar and concentric fibroplasia.

The stroma around the rete ridges appear more condensed and eosinophilic than the collagenous stroma in the papillary dermis. 

There may be some fibrosis in the papillary dermis together with patchy superficial chronic inflammatory infiltrate.

Host lymphocytic response around the vessels in the papillary dermis is prerequisite for the diagnosis of dysplastic nevus.

Architectural atypia (according to Ackerman et al.) includes 'shoulder phenomenon' characterized by peripheral extension of the junctional component, beyond the dermal component.

Reactive mononuclear cells are often present ; melanophages are noted in the upper dermis; there may be irregular distribution of pigment.

Radial growth phase melanoma is the most important differential diagnosis:

1.  The diameter is more than 5 mm (often more than 8 mm)

2.  Prominent host lymphocytic response in the papillary dermis

3.  Prominent cytological and architectural atypia.

4.  Pagetoid spread of atypical melanocytes is present.



Major Criteria :

-Basal (lentiginous and nesting) proliferation of melanocytes.

-Melanocytic atypia, lentiginous/epithelioid cell type.

Minor Criteria: 


-Increased vascularity with endothelial hyperplasia

-Concentric eosinophilic fibrosis / lamellar fibroplasia

-Bridging of epidermal rete ridges by atypical melanocytes

Surgical excision is the only therapy that should be done for dysplastic nevus.

Regular follow up is highly recommended for all patients with dysplastic nevus.  

All patients with dysplastic nevi should be educated about sun protection measures and self-examination techniques.


Further reading:

Dysplastic nevi and melanoma

Analysis of interobserver reproducibility in grading histological patterns of dysplastic nevi.

Reply to: "Histologically dysplastic nevi that extend to a specimen border".

The so-called dysplastic nevus is not dysplastic at all.

Clinico-pathological impact of fibroplasia in melanocytic nevi: a critical revision of 209 cases.

Favorable long-term outcomes in patients with histologically dysplastic nevi that approach a specimen border.

TSLC1 expression discriminates cutaneous melanomas from dysplastic nevi.

Novel multiple markers to distinguish melanoma from dysplastic nevi.

Seasonal variation in dysplastic naevi.

The dysplastic nevus: from historical perspective to management in the modern era: part II. Molecular aspects and clinical management.

Cutaneous melanocytic lesions: selected problem areas.

Malignant melanoma, dysplastic melanocytic nevi, and Spitz tumors. Histologic classification and characteristics.

Dysplastic changes in different types of melanocytic nevi. A unifying concept.

Dysplastic melanocytic nevi: a reproducible histologic definition emphasizing cellular morphology.



Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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