Good survival with primary dermal melanoma

Skin cancers

By Mardi Chapman

4 Jun 2020

Primary dermal melanoma can be managed in the same way as early stage primary cutaneous melanoma – with wide local excision and sentinel lymph node biopsy (SLNB).

According to a NSW study, uncertainty about whether primary dermal melanoma was a true primary or a metastatic lesion meant its management was also a clinical dilemma.

The study identified 62 patients with primary dermal melanoma from the Melanoma Institute Australia’s research database.

In the 51.6% of patients who had a SLNB performed, all of them were negative. The median Breslow thickness was 3.5 mm.

The study found the five-year overall survival was 87.1% and melanoma-specific survival of 91.5%. The five-year disease free survival was 66.1%.

“The overall recurrence rate of 37.1% within a mean follow-up period of 6.9 years is comparable to documented recurrence rates for stage II melanoma,” the authors said.

“Given the similar prognosis to stage II primary melanoma, which carries an 82-94% 5-year melanoma-specific survival, the present results support considering initial management as per primary cutaneous melanoma of equivalent thickness by way of wide local excision and a SLNB.”

The researchers said the findings supported the notion that tumours diagnosed as primary dermal melanomas were in fact true primary tumours and not cutaneous metastatic deposits from an occult or regressed primary site.

“One theory is that they arise de novo from non-epidermal melanocytes, melanocytes associated with dermal appendages or from dermal melanocytic remnants which were arrested in their embryological migration to the epidermis.”

However histopathological review of such lesions was critical.

They said it was possible that primary dermal melanoma might also represent an intermediate tumour in the biological progression from naevi to melanoma.

They noted the prognostic utility of SLNB in primary dermal melanoma remained unproven based on the negative SLNB status of all patients in this study.

“It may however be prudent to stage patients preoperatively with a PET/CT scan and MRI brain to exclude occult metastases, given the possibility of Stage IV melanoma.”

“It would also seem reasonable to restage patients postoperatively at 3-4 months and possibly again at 1 year with a PET/CT scan and MRI brain because of the possibility that they had Stage IV disease at initial presentation.”

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