You don't just want to say that you're an expert or have a lot of experience, but be a little bold here by stating that, although you find it very impressive here, you have noticed that there are some gaps in the total picture of care rendered and that you feel you can fill these gaps. This is a way of saying that selecting you will not only get this hospital or group what it needs, but even exceed its needs. You can further state that you can bring this hospital or group additional resources that most hospitals don't have, which would make this organization stand out above the rest. (These are the offerings that will make you particularly attractive, where you tout your special interests; special interests are specific aspects of one's specialization that do not have the bureaucratic designation of certification by a board.) For example, you may be board certified or board eligible in Dermatology, or even further trained (for example, in dermatopathology and Sjogren's syndrome), but you might say you have a special interest in autoimmune skin disease, as an example. This would sound very fortuitous to a hospital with a sizeable admission rate (or a group with a department) for autoimmune disease.