The healthcare sector is vast and includes everything from massive legacy companies including UnitedHealth Group Inc. NYSE: UNH and McKesson Corp. NYSE: MCK to tiny upstart pharmaceuticals firms. Investors looking to explore this sector thus have a choice about whether to focus on established companies with steadier business operations but, perhaps, less of a possibility of future growth, or on smaller firms that offer a higher-risk, higher-reward prospect. Fortunately, there are companies that fall somewhe ...