Recently saw dermatologist for a rash, he said that cutaneous t-cell lymphoma must first be ruled out. Since rash was drying up some, a biopsy was not done. Must wait till rash flares up. Should I see another type doctor for further diagnosis?

Well if you're uncomfortable with this decision for any reason you should seek out another opinion. But dermatologists are often on the front line when it comes to cutaneous lymphomas, for obvious reasons. If you went to a hematologist or oncologist, and you had no evidence of skin lesion, and you had no other accompanying symptoms and they did an exam and found nothing, there's really very little they could do. They could do a PET/CT to look for cancerous nodes, but if they have no reason to order one, they probably wouldn't order one. And without any obvious nodal involvement, and without any visible skin lesions, they have nothing to biopsy.

Do you expect this rash to return? I mean is it recurring? Ultimately, you have to decide what's best for yourself- second opinions are almost always a great idea and should never be discouraged.

If you want to see someone else (and you're in the US), look into a hematology oncology department at a comprehensive cancer center, because T-cell lymphomas are notoriously hard to diagnose. Go straight to the experts.