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Dr Louise Photiou, Registrar, Victorian Melanoma Service, Alfred Hospital, Melbourne, VIC, Australia; Dr Nikki R Adler, Adjunct Senior Lecturer, St Vincent's Hospital, Melbourne, VIC, Australia; Dr Andrew Haydon, Consultant, Medical Oncology, Alfred Hospital, Melbourne, VIC, Australia; Prof Catriona A McLean, Head, Anatomical Pathology, Alfred Hospital, Melbourne, VIC, Australia; Prof John W Kelly, Consultant, Victorian Melanoma Service, Alfred Hospital, Melbourne, VIC, Australia; A/Prof Victoria J Mar, Director, Victorian Melanoma Service, Alfred Hospital, Melbourne, VIC, Australia. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell/Maria McGivern. November 2018.
Primary dermal melanoma, also known as solitary dermal melanoma, is melanoma that is confined to the dermis without an epidermal (junctional) component. It can sometimes be difficult to differentiate from a cutaneous cutaneous melanoma metastasis .
Primary dermal melanoma has been proposed as a distinct subtype of melanoma due to the observation that patients with this type of presentation have a much better prognosis than those with a true cutaneous melanoma metastasis [2,3].
Both sexes are at equal risk of developing a primary dermal melanoma. The average age at diagnosis is 51.2 years, within an age range of 8–83 years . No ethnicity data has been reported for primary dermal melanoma.
Primary dermal melanoma may not be recognised as a melanoma and the classic ABCDE criteria for melanoma may not apply. A primary dermal melanoma is usually the same colour as the skin and presents as an elevated, firm, growing nodule.
The complications of primary dermal melanoma include recurrence and metastasis. However, the incidence of recurrence and melanoma metastasis is low in published case series of patients with presumed primary dermal melanoma [1–5].
The diagnosis of primary dermal melanoma is a difficult one and it requires clinicopathological correlation. It is often difficult and sometimes impossible to distinguish between primary dermal melanoma and cutaneous metastasis histologically. A detailed medical history should be taken to exclude a previous melanoma that may have produced a cutaneous melanoma metastasis.
The pathologist will usually report a nodular melanoma without an in-situ or junctional component and that it is contained entirely within the dermis. Regression and ulceration may be seen and can be attributed to prior trauma.
The differentiation mostly relies on a thorough clinical history of a growing lesion, examination findings, and clinicopathological correlation. This differentiation is very important as it confers significant prognostic and therapeutic implications. The most important differential diagnosis for a primary dermal melanoma is a cutaneous melanoma metastasis.
Most primary dermal melanomas do not look like typical melanomas and are usually excised with the provisional diagnosis of a basal cell carcinoma, squamous cell carcinoma, SCAR, dermatofibroma, cyst, blue naevus, or haemangioma [1–3].
As primary dermal melanoma is a cutaneous melanoma, the treatment should be as for any other cutaneous melanoma and follow the most current American Joint Committee on Cancer (AJCC) guidelines .
Patients with primary dermal melanoma should be given the opportunity to have a sentinel lymph node biopsy and be investigated appropriately for suspected distant disease with careful follow-up.
It is also important to perform a full skin examination to exclude the occurrence of another cutaneous melanoma.
The importance of a correct diagnosis of primary dermal melanoma is linked directly to the observation that patients with primary dermal melanoma do well compared with other patients with melanoma. The current literature cites survival rates of 73–100% at 3–5 years [1,5], compared to a survival rate of 52% at 5 years for patients with a cutaneous melanoma metastasis .
Primary dermal melanoma may sometimes progress to metastatic melanoma .
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