in-situ melanoma versus severely aytpical mole

Two years ago, I noticed that a mole on my chest looked a bit unusual and went to my family doctor and asked him if I should have it biopsied. Even though he recommended against it, I was cautious and insisted that it be biopsied. The results came back as "in-situ" melanoma and I had it removed immediately. I've been told that "in-situ" melanomas are sometimes referred to as "pre-cancerous", but that is often misunderstood. I noticed several other moles on my chest and shoulders and they all looked slightly suspicious- and I had them all biopsied (approximately 10 more). Two came back as moderately to severely atypical and my dermatologist removed them both- but insisted on sending the results to a different lab (Univ. of Penn.) than had been used previously (in his view U. of P. is a higher quality lab). My question is this- Is it possible that the first biopsy was actually a severely atypical mole and misdiagnosed? My family has no history of skin cancer or melanoma. In addition, is it normal that moderately-severely atypical moles turn into melanomas- or was my dermatologist just playing it safe? I'm comfortable with that- but would like to know some statistics on this... How likely is it that since I've had these develop that I will develop another "in-situ" melanoma? Am I in a very high risk group- or can I calm down a bit? I could use some reassuring advice...