Shari Redstone, the media mogul who has been trying to sell Paramount in a politically fraught transaction, is undergoing treatment for cancer.

Ms. Redstone, who is trying to close the sale of her family’s Paramount media empire to Skydance, was diagnosed with thyroid cancer this spring.

Shari Redstone, who for months has been leading the charge to merge Paramount with Skydance has, at the same time, been fighting another battle with thyroid cancer.