Is there a definition of neighborhood ... try this description on for size:
"A property is an integral part of its surroundings and must not be treated as an entity separate and apart from its environment. The value of a property is not found exclusively in its physical characteristics. Physical, economic, political, and sociological forces found in the area interact to give value to a property. In order to estimate the value of a property, an analysis of the degree of influence extended by these forces upon a property must be made of the area. This area is commonly referred to as a market area or neighborhood. A neighborhood or market area can be a portion of a city, a community, or an entire town. Usually considered to be an area within which a high degree of similarity of use or a grouping of complementary uses. A neighborhood or market area is, therefore, a more or less unified area with somewhat definite boundaries."
To answer your question about the location of comparables being outside of the subject neighborhood ... it depends. There is not a specific rule or requirement, but common sense should dictate.
- Are there sufficient transactions within the neighborhood to adequately perform the analysis? Were there specific transactions within the neighborhood that appear to have been specifically ignored?
- Is there a specific feature or characteristic that would necessitate expanding the "market area"?
- How comparable is the area from which the appraiser chose to go for data?
Your issue is not cut and dry, there is no single answer which is why appraisal review is not just checking off boxes either.