Diagnosis code

I need help with a diagnosis code. I have an op note with a patient that has a base of tongue biopsy and the diagnosis code given is squamous mucosa with no carcinoma. The patient however has a spindle cell carcinoma of the neck with unknown primary.
My question is:what diagnosis code do I use for the squamous mucosa of the base of tongue?

Thanks,
Jenny, CPC

re: Diagnosis code

from my understanding, squamous mucosa is normal tissue so maybe something benign