4Tel Aviv University, Israel
Zamir H is currently working in the Departments of Dermatology, Rambam Health Care Campus and the Bruce Rappaport Faculty of Medicine, Haifa, Israel
Background: PDM is a rare variant of melanoma. It is confined to the dermis and/or subcutis without epidermal component. Hence, histologically alone, it cannot be distinguished from a melanoma metastasis. Careful clinical history, examination and proper imaging are required to exclude metastatic disease. Diagnosing such a lesion as PDM or as a metastasis has significant impact on the proper management and on the prognosis.
Our experience and insights cast some light on this problematic clinical situation.
Methods: We retrieved all 36 clinically diagnosed PDM patients from our prospectively collected database of 1600 melanoma patients surgically treated in a tertiary melanoma center between 1995 and 2015. Strict focused pathology revision excluded 23 patients who failed to meet all criteria for PDM set forth by Swetter et al. 13 patients were in-depth investigated regarding clinical, histopathological parameters, surgical treatment and outcome.
Results: 13 PDMs, median "thickness" – 5.5 (range 2 to 11) mm, median mitotic rate 4 (range 0 to 17)/mmsq, formed this series.11 pts (84.6%) are still alive after median follow up of 56 (range 12 to 120) months. 3 of 13 patients had a positive sentinel lymph node followed by completion dissection.
It seems that when PDM is diagnosed, it can be successfully treated as a primary melanoma (rather than a metastasis) including Sentinel node sampling and completion dissection
The actual "thickness" of these melanomas, as well as their mitotic rates, are associated with better prognosis than same-thickness cutaneous melanomas.
Conclusions: Diagnosing PDM demands careful clinical and histological reviews. PDM has favorable outcome compared to primary cutaneous same –thickness melanoma. Wide local excision and Sentinel lymph node biopsy seem appropriate and worthwhile, once these lesions are deemed primary melanomas