Any activity that takes an input and changes it to produce an output, is by definition, a process. In sales we take leads and make them into customers. By definition, sales is a process.
Sales is a unique process. While all business processes are based on customer needs, only in sales is an external customer an active participant in the process. Consequently, process and quality improvement methodologies need to be worked with extensive experience in selling. The tools are the same, but application can vary.