Lipomatous hamartoma of the orbit. Proliferations of mature adipose tissue, while common in retroperitoneal and subcutaneous sites, rarely occur in the orbit. We describe the clinical, radiographic, and histopathologic findings of a nonencapsulated lipomatous tissue overgrowth of the right orbit in a 35-year-old man. The mass had caused proptosis since childhood and was apparently present since birth. Due to the age at onset, the histologic similarity to normal orbital fat, and the lack of encapsulation or choristomatous elements, we propose the term lipomatous hamartoma for this entity. 