Chances lymphoma with no noticeable enlarged lymph nodes? CBC, CMP normal. CT normal- mildly enlarged spleen 13cm

Very Low chance. It is reassuring that there aren't any enlarged lymph nodes, and you have a normalCBC. If there is a lymphoma, it is a very hard to detect one. And it is not causing any problems to the body. I would leave it alone. Get a check up maybe in 6 months- just labs, ldh and a physical exam or ultrasound for the spleen. Spleen sizes also vary quite a lot, but good to keep an eye on it.