Does Black Spots In Mucus Indicate Cancer?
well.... not normal.....
Detailed Answer:
ok.... lung cancer at under age 30 is about never. Literally, unknown HIV with AIDS related lung fungal infection is more common. Also, holes in the lung from previous injury and collection of gunk in these areas and repeated pneumonias is also more common (called bronchiectasis).
And... the cause that I actually have seen in patients (and see basically on a weekly basis... REALLY COMMON) is lung healing and getting up over a decade of gunk that collected in the lung. Note that the rest of the sputum is CLEAR, not inflamed, not infected.
Furthemore, running opens up the lung and allows the gunk to get mobilized. Hydration and perhaps guafenesin might improve the mobilization.
Bottom line, this is likely a sign of returning lung function, lung healing, and getting rid of junk out of it and likely a GOOD sign. Cannot say for sure in your particular case without an exam. Online information is no substitute for direct exams with/without x-rays.