Read above argument about adeno or squamous ca. Some times it is difficult to tell squamous ca from adenocarcinoma in cytology. However it is very easy by using IHC.

For this case if we can rule out mesothelial origin (calretinin negative), then we know it is a cancer case.

Next step we need to figure out the possible origin, including squamous vs adeno.  How? We need IHC stains

P63, ck5/6 for squamous ca, mucicarmin stain for adenocarcinoma

CK7/ck20

TTF1

Of cause we need to have clinial correlation with imaging results