There are pullbacks in uptrends and then flat out trend reversing breakdowns. We never know for sure which is which until history plays out. But Biogen’s (BIIB) massive selling on Friday has all the makings of the latter. Any time a company rises more than ten fold in less than five years, it’s generally due to very strong core growth. The one thing investors do NOT want to see is the cutting of growth forecasts. That’s what BIIB did on Friday when they released their latest quarterly results, cutting their revenue forecast from 14-16% growth to just 6-8%.