A "hypo-dense foci in the left thyroid lobe" was found during ct w/ contrast of head and neck. what does this mean?

Cyst?: It could be a cyst. Follow up with your doctor on it.

Hypo:Low; Hyper:High: Most medical terminology just descriptive, not implying any great understanding or insight. Foci means “spot”, location. Go slow, look up terms. The thyroid is a cystic gland, i.e. Cells which manufacture & secrete proteins into the water around the cells & producing accumulations of extracellular material. Lower density than surrounding tissue c/c/w cyst, just ? Larger than usual, ca ↓↓↓ likely.