Is a Spiculated lung nodule always malignant?

I applaud your research efforts. I think the "up to 90%" comment tells the story. I had nodule (RUL) removed sixteen months ago. It was spiculated, and it was malignant (stage 1b). The wording on the CT scan can be informative. My first CT scan noted it was spiculated and said it could be cancer, scarring or something else. (I had quit smoking 20 years before). The CT scan suggested a PET scan and the PET scan "lite up" in two areas. I had biggest nodule removed 16 months ago and now about to remove the other.
I have multifocal lung cancer so have other nodules that are considered cancer and they wait until they get to a certain size before treating. They want to preserve lung tissue. They monitor nodules with CT scans but also check them with PET scan which tells a lot.
If you have any doubts, seek a second opinion. I did. Look for Pulmonologist with specific focus in lung cancer.

What size was your nodule?
Due to the small size of my nodule Biopsy and Petscan won’t be meaningful.
So doctor suggested the watch and wait approach.
My doctor said that infection, inflammation is a possibility and if it shows any growth on next scan we’ll do surgery.
But given all the data regarding spiculated lung nodules with the up to 90% it’s hard to believe that I will be one of the rare cases where it turns out to be just infection or inflammation..
However the data and studies also mostly refer to nodules that are > 1cm.
Not much information is available on smaller nodules with Spiculation, So I don’t know if the risk of 90% applies to smaller nodules as well?
According to The Fleischner guidelines for smaller nodules with suspicious borders such like Spiculation a follow up in 3-6 Months is recommended.
I think it’s just a matter of time till my nodule grows and is then confirmed malignant and with any growth the possibility of it spreading increases.
Therefore I’m debating whether I should just insist on getting surgery right away to get rid of it as soon as possible.

They removed a 3.1cm mass from my upper right lung (stage 1b not 1a because of size). However, the measurements on CT scans refer to ground glass, semi solid and solid parts so it is difficult to compare to your 5mm. Did they say it was solid or semisolid?
I have three and six month follow-up scans and they know my other nodules are adenocarcinomas (all thought to be primary cancers). But the objective is to preserve lung tissue/capacity for quality of life so one can't just cut them out. My two largest nodules were in good locations for surgery. And I am having Video Assisted Surgery which is a lot easier on a person. My other nodules will probably have radiation …and they want a certain size for that also.
I relate to your desire to do something. I am the same.
Look for a Pulmonologist who specializes in lung cancer (Pulmonologists specialize in certain areas), and be sure the institution offers the latest treatment options for lung cancer – like Video Assisted Thoracic surgery and more advanced radiation, other targeted therapies. An experienced Specialist will know when and how to treat.