Dear honey bun, Was the report the radiologist's report or your doctor's recommendation after putting the information from the reports into context of your situation (physical exam, any history of symptoms)? If there is not a good explanation for this 2cm mass, the follow up testing would hopefully help to determine more about what this is. A month is not an unreasonable amount of time. Depending on the results of the further testing would help to determine next step in the evaluation, which could be a biopsy, if the mass is still present and cannot be explained.
I would strongly feel that an FNAC or Core Biopsy shall releive you from all anxiety you are having to put you on the right track of any medical care needed with your symptoms.
breast tissue can become engorged before and partway into menses, and this can affect mammography. What makes more sense to me is having the followup a couple of weeks after finishing menses, rather than a month later which would be in more or less the same time in the cycle. How best to proceed in each situation is not always clear-cut; it takes being able to see the xrays, do the exam, etc. When there are questions, then judgement is used to decide when it's ok just to follow along, versus doing some sort of biopsy. As long as the doctors involved agree everything looks ok, then keeping a close eye as they are doing ought to be safe.