Small swelling under lower eyelid, with dermatitis around. dermatitis cleared with eumovate - came back when i stopped. can it be sebaceous carcinoma?

Uncommon: That is uncommon but certainly possible. See a dermatogist or eye doctor who specializes in eyelid conditions for check and maybe biopsy.

Answer: There is unfortunately know way of truly telling you what it may or may not be without examining it physically. And the only definitive answer is with a biopsy to know for sure what nay lesion is. Good luck.

If it was cancer: it would not go away with a topical steroid. Eyelid dermatitis can recur, most commonly from mascara or nail polish