Primary Dermal Melanoma

That’s great news that PDM did not spread. I didn’t find much searching Google Scholar, but here is one abstract that might be reassuring to you about good outcomes: https://www.sciencedirect.com/science/article/abs/pii/S0748798320304406

Wishing you well!

First, sorry for your diagnosis and you have joined our group.  I have looked at a lot of the research on Primary Dermal Melanoma since 2014 since this was a potential brought up with my husband’s pathology of his punch biopsy before he got this “tumor” removed surgically in February 2021.  His was 19mm deep (22 mm wide) with mitotic rate of 8, no regression identified, no epidermal component etc. His surgical pathology report from his surgery at MD Anderson states that based on the architecture of the lesion, the findings are consistent with metastatic nodular type melanoma but it may correspond to primary melanoma. His margins were clear and all his scans came back clear a month later.

Just to provide some background for about 7 years before his diagnosis he had this weird skin growth in the same place that he asked his doctor if he should be concerned about and general practitioner said no.   It went away completely for about a year and then he said one morning he woke up and felt like he was laying on a golf ball and there was quite a large bluish nodule in the same spot.

So Dr. Susan Swetter (Stanford) was involved in Primary Dermal Melanoma research originally from the VA in California back in 2004.  They believed they saw a small group of patients that had these large nodular-like solitary melanomas that were well-circumscribed with no epidermal component (technically classified Stage 4) found that for some reason had significantly longer survival than would be expected with the characteristics of their “tumors” (breslow depth is high, mitotic rate is high, spindle/epithelial cells, etc) and less aggressive biological process possibly that does not behave like normal Stage 4 metastatic disease and did not spread as quickly.  At this time, there was no way to histologically (staining the tissue and looking at it microscopically for various markers) distinguish between primary dermal melanoma and nodular/metastatic and the literature shows different thoughts on this today.  another study (retroactively looking at records of melanoma patients) at University of Michigan VA also showed a group of melanoma patients with stage 4 nodular-like solitary melanomas that had less expected spread  such as +SLNB, distant spread, etc. They believed this might be a distinct subtype of melanoma that was behaving as a primary and should not be considered Stage 4 but compared more to Stage 1-2 cutaneous melanoma in terms of prognosis and rates of recurrence, etc.. So possibly this is the primary that has fully regressed or actually arisen from subcutaneous tissue rather than skin down as other melanomas do and instead of some sort of  true cutaneous metastasis from a primary elsewhere in the body.  And there was a look at a group of patients in Australia as well and I’ve included these links below and here is synopsis:

By AJCC convention, these cases are classified as stage IV metastatic disease. Our data suggest that these presumed metastatic tumors do not behave like stage IV metastatic disease to the skin via lymphatic or hematogenous spread from an unknown primary site; rather, they are behaving like primary tumors originating in the dermal and/or subcutaneous tissue.

The absence of nodal or distant metastases and the prolonged survival, greatly exceeding that expected, suggest that in our patient a metastatic origin of the disease is unlikely. Instead, we hypothesize that the tumour may represent a primary dermal melanoma or, alternatively, a primary melanoma with regression of the epidermal component, despite the lack of any sign of ongoing histological regression. Moreover, clinical and histological features allow differential diagnosis of this entity from other dermal melanocytic lesions, including cellular blue naevus, malignant blue naevus, epithelioid blue naevus, and animal-type melanoma.^5, 6 Further studies are warranted to better clarify the histogenesis of these unusual melanocytic proliferations.

There is also some similarities with the research for what they called Stage 4 with unknown primary.  These tended to also be typically large, well-defined solitary melanomas with no skin component seen (so is it the primary or metastases from unknown primary elsewhere?).

With all the links and text I copy and paste below, the thing I think it is important to remember is that while it can be important to have the correct pathological/histological diagnosis, Melanoma is Melanoma so the key is to still be diligent and follow the typical protocol for “high-risk” melanoma.  There are now more possible treatment options for people that are no evidence of disease as well after resection/surgery.   Any melanoma can recur or metastasize.  I hope you never do and melanoma never comes back and as Celeste would say, live your life, but it is important to monitor no matter what your ultimate treatment choices that are given to you and I would also recommend that you have your tumor genomically tested just to have information if it was not tested yet.  There has been an incredible amount of advancement in treating based on the mutations you might have that are “driving” the cancer growth.  This is incredibly important knowledge to have in your arsenal.

My husband was considered No Evidence of Disease after his surgery and scans and his SLNBs were negative, but adjuvant immunotherapy was not yet approved, so he has done wait and watch for 7 years.  Quite honestly, he probably would have done that anyway, while I would have gladly signed him up for any trial and any therapy, especially immunotherapy!  His tumor also has the NRAS mutation.      My husband’s doctor at MD Anderson treated him as Stage 4 nodular melanoma patient with no evidence of disease at the time and did not believe the distinction of primary dermal melanoma was particularly useful and put him on the standard protocol of scans every 3 months for 2 years, every 6 months the next 3 years with Brain MRI yearly.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2673232/

https://pubmed.ncbi.nlm.nih.gov/11074704/

https://pubmed.ncbi.nlm.nih.gov/32417156/

https://pubmed.ncbi.nlm.nih.gov/19130137/