Night sweats can be common in certain medical illness like cancer and infections. It's also common in peri-menopausal women. Night sweats can also occur with untreated obstructive sleep apnea (OSA). In my experience, this is usually from severe OSA and typically involved the shoulders, neck, and head.
Here is a case report from the Journal of Clinical Sleep Medicine that describes a patient that had severe night sweats from mild OSA. The night sweats were eliminated by use of CPAP. And this patient happened to also have a form of lymphoma, which would make most physicians think that the cancer is the cause of night sweats. The report author suggest sleep evaluation in patients with regular night sweats to look for OSA.