I'm sorry to say, but it probably is gyno. Awhile ago I got gyno (and pain) in my right breast (just tenderness in the left breast) from an M1T cycle. Sounds like a similar situation to yours. My lump was the nodular type, about the size of a peanut M&M I would estimate. After 20 mg/day of Nolva for 3 months it was gone-- no lump, no pain. My "research" experience was with liquid tamoxifen citrate from Lion Nutrition (peppermint flavored).