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Variants of Melanoma that can be mistaken for a Benign Lesion :

 "Wolf in Sheep's Clothing"

"Mistaking an aggressive malignant tumour for a benign harmless lesion can lead to disastrous consequence"

Dr Sampurna Roy MD               





Histolopathological examination of melanocytic lesions constitutes a large proportion of a pathologist's daily workload.

These lesions are excised either for cosmetic reason or when they are clinically atypical and excised to rule out melanoma.

Dermatologists, surgeons, and oncologists depend on the pathologist for a prompt, accurate and complete diagnoses in a case of melanoma.

The histological diagnosis of benign melanocytic nevi and malignant melanocytic lesions can be readily made in straightforward cases, by applying the well-recognized pathological criteria.

A large number of melanocytic lesions fall into a borderline area that can be a problem to the most experienced of pathologists.

Some pigmented skin lesions can be difficult to classify due to unusual features.

One should avoid making both under and over diagnosis of melanoma by systematically approaching these lesions.

Diagnostic error can delay appropriate clinical management of the patient and may lead to legal problems.

The following variants of melanoma may mimic benign lesions and should be carefully examined to establish the diagnosis.

For more information on these lesions please follow the links :

- Desmoplastic melanoma

  Microscopic images of Desmoplastic Melanoma

- Spitzoid melanoma

- Balloon Cell Melanoma

  Microscopic images of Balloon Cell Melanoma

- Nevoid Melanoma

  Microscopic images of Nevoid Melanoma

- Regressed Melanoma  

Key features are:

(1) Epidermal thinning with loss of rete ridges,

(2) Minimal or absent atypical junctional change, and

(3) A subepidermal band of angiofibroplasia (often up to 0.8 mm thick), which may variably contain a few lymphocytes, melanophages, and an occasional melanocyte.

(4) Capillaries are usually slightly increased.


Further reading:

[Cutaneous regressing/regressed malignant melanoma: a clinicopathologic analysis of 8 cases].

Pitfalls and important issues in the pathologic diagnosis of melanocytic tumors.

Problematic pigmented lesions: approach to diagnosis.


Detailed clinical history is essential before looking at a pigmented lesion. The following information should be provided to the pathologist:

1) Age of the patient

2) Site of the lesion

3) Whether there was any previous history of shave biopsy or incomplete excision.

The entire tissue with lesion should be examined, with levels cut where appropriate.


General features in favour of Melanoma:

1) Asymmetry

2) Peripheral epidermal invasion

3) Heavy pigmentation

4) Deep and abnormal mitosis

5) Nuclear pleomorphism

6) HMB45 positive deep dermal cells

7) Vascular invasion, neurotropism, satellites

Ref:  Melanocytic lesions of the face: Diagnostic Pitfalls.






Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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