This is not a request for medical advice. I found out someone I know was diagnosed with cancer, and I want to get some idea of what’s going on based on what little second-hand information I have. All I know was that this person was diagnosed with melanoma (yes, I know that alone means “pretty serious”), but the primary site was not found. Does this likely mean it has metastasized already, and melanoma cells were found elsewhere in the body? Any speculation on prognosis?
You have to look at melanoma as the starting point. Okay, someone has melanoma. The dangerous thing about it is that melanoma is very likely to metastasize. It can be found on various parts of the skin…different areas, but I don’t believe that means it metastasized – the skin is one organ.
If cancer shows up somewhere else, other than the skin, then it has metastisized (unless it is a huge coincidence that say liver cancer developed on its own simultaneously).
usually the melanoma is surgically removed and then may or may not be treated with radiation
it might not be that bad, but you never know
Thanks, but what I’m really confused about is “no initial site found” - at least I think that’s what I was told. How does that happen, and if it isn’t found, how would they diagnose melanoma?
Sounds like a bad situation. Finding melanoma in an obvious metastasis rather than at a primary skin site means the cancer has spread. Excision alone is no longer a viable treatment. Chemo and possible radiation would probably be called for along with possible debulking, interferon, etc. etc.
It is not unusual to find melanoma by metastasis but not find the primary skin lesion. Sometimes the primary lesion resolves after the cancer has spread. I wish we knew why it happens, so we could use it to treat patients.
Melanoma that has already spread is difficult to treat and results in death far more often than not.
Sorry. 
Oh, and essentially you diagnose melanoma in a metastasis by looking under the microscope and seeing lots of melanoma cells in the tumor.
How does that differ from looking at the primary site?
Well, it think the mets can be anywhere - like in a lung or a liver or a brain or whatever. If they did a biopsy of a growth in such a site, and found a boat-load of melanoma cells, they would know that it was a met, as opposed to a primary cancer. I think…
Damn. That’s what I was afraid of.
But thanks for the straight answer.
That is essentially correct. Trouble with melanoma is that, besides the “unknown primary site” problem that Qadgop mentioned, it can metastasize to just about any site imaginable.
Without a known cutaneous primary, you’d also want to do a few confirmatory immunohistochemical stains (e.g. HMB45, MART-1) to confirm the diagnosis of melanoma as well, since melanoma cells can often mimic primary carcinomas in appearance.