Poster Presentation 35th Lorne Cancer Conference 2023

Primary dermal melanoma systematic review (#230)

Lawrence Lin 1 , Zhao Feng Liu 2 , Ibukun Oloruntoba 1 , Ojochonu Anthony 1 , Timothy Widjaja 1 , Raaisa Islam 3 , Chris Wong 1 , Firdavis Feierdaiweisi 1 , Heiu Ha 1 , Christopher Chew 1 2
  1. Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia
  2. Department of Dermatology, Alfred Health, Melbourne, Victoria, Australia
  3. Department of Research, The Skin Hospital, Sydney, New South Wales, Australia

Background and Aims: Primary dermal melanoma (PDM), also known as solitary dermal melanoma, is a rare and distinct clinicopathological subtype of cutaneous melanoma with relatively favourable prognosis when compared to those with an epidermal component of similar Breslow’s thickness (1). We aimed to review and synthesise the clinical and pathological features of PDM.

Methods: A systematic literature search was conducted on MEDLINE and Embase following PRISMA guidelines [CRD42022356844] on all peer-reviewed, English-language studies that reported one or more cases of PDM. Key search term used was “primary dermal melanoma.”

Results: A total of 24 studies with 317 patients were included for analysis. The weighted mean age was 56.6 years and a slight male-skewed gender predisposition (Male:Female 1.32:1) was present (Figure 1). Lesions were fairly evenly distributed on the extremities (36.0%), trunk (33.4%), and head/neck (27.4%) (Figure 1). Mean weighted Breslow’s thickness was 6.32mm, 46.3% of melanomas had a Breslow’s thickness greater than 4mm, and only 9.3% was less than 1mm. Mean mitotic count was 4.4 and 97.1% of PDM had at least 1 mitosis. 183 (57.7%) patients underwent nodal assessment with sentinel lymph node biopsy and 26/187 (14.2%) were positive, suggesting evidence of metastatic disease to regional lymph nodes. Median follow-up was 24 months and the five-year survival amongst patients who were followed up was 184/249 (73.9%). PDMs located on the trunk had the highest rate of regional lymph node metastasis on sentinel lymph node biopsy nodal assessment with a 21.7% positive rate. As expected, mitotic rate and Breslow’s Thickness had a linear correlation, however likelihood of lymph node metastasis was surprisingly lower in the higher risk T4 primary tumours compared to both T1 and T2 primaries (14.3% vs 20% and 20% respectively).

Limitations: There were often missing clinical and pathological data in published studies. Recurrence and survival rates were not frequently reported - limiting applicability to clinical care.

Conclusions and Significance/Impact: PDM is a rare and poorly understood subtype of melanoma. Further research is needed to identify relevant clinical, pathological, molecular and prognostic features of PDM to improve overall and recurrence free survival.

  1. 1. Simonetti O, Molinelli E, Brisigotti V, Brancorsini D, Talevi D, Offidani A. Primary Dermal Melanoma: A Rare Clinicopathological Variant Mimicking Metastatic Melanoma. Dermatopathology (Basel). 2021;8(1):29-32.