You can take it as "most likely caused by asbestos," but I've read different figures and claims, with no time or expertise to validate any of them.

One site said asbestos is the ONLY cause of mesothelioma. (Seems a bit presumptuous)

One site said asbestos is the only KNOWN cause of mesothelioma. (Perhaps a more supportable claim)

One site said asbestos is known to be associated with about 80% of mesothelioma cases.

One site said asbestos are/were often present in other naturally occurring products that had not been purified to remove it (e.g., talcum powder, makeup), so it could still be asbestos sneaking into your life.

One site even said second-hand exposure to asbestos (via spouse's clothing, etc) could be a cause.

I don't recall any of them clarifying whether those claims pertained specifically to pleural mesothelioma (around the lungs) vs peritoneal or other body parts.

One piece of data you'll want from your oncologist (after location -- pleura, peritoneum, etc) is the cell type: epithelioid, sarcomatoid, or bi-phasic (combination of both). That would be confirmed by a very close inspection of your pathology slides, and may warrant a second, independent read of the slides to confirm, since it dictates which treatment you might receive.

My 85-year old father is in the late stages of his battle with malignant pleural mesothelioma. The first lab to look at his slides diagnosed it as epithelioid (I think), but a more expert second opinion also found sarcomatoid cells, re-classifying it as bi-phasic.

I will recommend you immediately begin your search for a mesothelioma specialist, unless the oncologist you're planning to see is one already, because this is still kind of a rare disease for oncology generalists and even for a lot of lung specialists.

Another recommendation is that you get at least two genetic tests done as soon as possible, so you can have results as soon as possible, which may enable you to get the right treatment sooner or begin with a clinical trial that you might otherwise be ineligible for by starting with some other treatment first.

One of the genetic tests would be a "germline" test to look for hereditary mutations passed down from your parent(s); Invitae is one example of such a test. The other type is for "somatic" mutations (those caused by the environment; Guardant 360 is one example of several available. My dad's small-town oncologist was reluctant to order either one, but eventually ordered both after I insisted (based on my own previous test showing an ATM mutation, discovered while treating my pancreatic cancer).

There is a third test, from Grail (https://www.galleri.com/what-is-galleri/types-of-cancer-detected#block-glossary-45819) that claims to detect malignant pleural mesothelioma, and might be a nice, non-invasive data point to either confirm or question other results, or detect the possibility of other cancer DNA in your bloodstream. It's not an FDA-approved test, and would probably cost you $950 out of pocket, and my experience with it was disappointing (failed to detect recurrence of my pancreatic cancer).

In short, your treatment options are probably traditional chemotherapy, immunotherapy, and/or surgery (depending on your overall fitness and degree of spread). Knowledge of any mutations/fusions you possess will help guide the treatment, and the sooner the better.

I don't have a lot of answers, but between my own cancer and watching my dad's battle this past year, I've learned a few things. Feel free to send me a direct message if you'd like to talk more. Wishing you the best!