A cyst on supraclavicular fossa, has lasted over 2 months and got bigger, not hard, but is noticed. 7.5*3.4 measure. location, size means lymphoma?

Can't tell: Only way to establish lymphoma is a biopsy. Physical exam can be very misleading. In that area, could be lots of benign things as well. I assume you mean centimeters, right? See your doctor for evaluation.

Not always: You need to go to the doctor to get checked. You may need an ultrasound and a biopsy to determine the nature of the cyst which could be benign or could be lymphoma. Usually lymphoma is associated with other symptoms. Go to a doctor asap though.