CUTANEOUS MELANOMAS AND MDN:
Just an overview to capture some knowledge about the MDN and its atypia:
Early detection of melanoma carries an excellent prognosis, with surgical excision often beingcurative.
Factors leading to early diagnosis and effective treatment are critical.
Clinical history is essential for accurate diagnosis. Acronym ABCDE – asymmetry, border irregularity, color variegation (2% to 8% of melanomas are reportedly
amelanotic), diameter over 6 mm, evolution or changes in
a previous nevus. Other important information includes
site and duration of lesion, history of prior biopsy/trauma
(such as excoriation) at that site, recent sunburn/sun
exposure, personal history of previous melanoma, family
history of melanoma, and age of the patient. The age of
the patient is of particular importance.
Cytological atypia and pagetoid spread frequently seen in
dysplastic nevi may be features of several other benign
melanocytic lesions, such as genital type nevi, acral nevi,
neonatal or childhood nevi and recurrent or traumatized
nevi.
Whenever possible, complete or large excision
should be made to permit histological assessment
of the entire lesion.
The proper method of biopsy and definitive surgical excision
of cutaneous melanoma is vital for optimal patient outcome.
. Superficial shave biopsies frequently preclude
the accurate assessment of Clark's level and tumor thickness
of melanomas. This uncertainty may result in a
recommendation for complete excision after an initial small
biopsy so that the residual lesion can be studied.
Any biopsy performed detect the histologic features that give rise to clinical atypia is always better for the better prognosis.
According to the American Academy of Dermatology (AAD)
guidelines2, whenever possible, the atypical lesion should
be excised with narrow margins for diagnostic purposes.
The following considerations are recommended for biopsy:
1. A narrow margin, excisional (bda) biopsy is considered
the procedure of choice for adequate histologic
examination.
2. An incisional biopsy technique is appropriate when the
suspicion for melanoma is low, when the lesion is
large, or it is impractical to perform a complete
excision. In such cases, multiple biopsies of different
regions are warranted, because a solitary biopsy may
not represent the worst area of the lesion in up to
40% of cases.
3. A repeat biopsy should be performed if the initial
biopsy specimen is inadequate for accurate histological
diagnosis or staging.
4. Fine needle aspiration cytology should not be used to
assess primar y cutaneous and mucosal tumors.
Dysplastic Nevus should be considered a potential
precursor lesion to melanoma and requires careful
surveillance and prompt treatment.
About one-third of melanomas arise from preexisting nevi
(both acquired and congenital types), whereas the
remainder appear to arise de novo. The melanocytic
dysplastic nevus (MDN) remains a controversial issue, and
contrar y views about its existence are reported in the
literature. Part of the problem with these lesions is the
lack of a precise definition. The consensus statement issued
by the National Institutes of Health in 1992 required the
presence of architectural disorder only (and not cytological
atypia) to establish a diagnosis of dysplastic nevus3. To date,
however, most dermatopathologists believe that both
architectural and cytological atypia must also be present.
The cytological atypia in a dysplastic nevus is generally
random and patchy, with atypical cells punctuating a
background of cells with minimal or no atypia.
Several groups have demonstrated epidemiological,
morphological, immunohistochemical and molecular
differences banal nevi, dysplastic nevi and
melanoma, supporting the view that dysplastic nevi occupy
an intermediate position in the hierarchy of melanocytic
lesions and may be precursors of cutaneous malignant
melanoma4,5. The clinical relevance of MDN lies in its
association with an increased risk of cutaneous malignant
melanoma.
According to the AAD guidelines, atypical
lesions should be excised with narrow margins of about
2-3 mm for diagnostic purposes, whenever possible.
Most often, clinicians do not include treatment recommendations for mildly atypical dysplastic nevi that appear to have been completely
excised or are focally present at the margins.They suggest
conservative re-excision of dysplastic nevi with moderate
atypia that extend to a margin. If the margin is substantially
involved, advising a complete excision is essential. They adhere to
the standard recommendation of 5 mm margins in all
severely atypical nevi that involve the margin. they include
in their reports a measurement to the closest biopsy margin
in severely atypical nevi.
These are the general outlines for the MDN we come across.
