It's historical. I found it in a quote from one of the former curators. World War II confirmed the Army Medical Museum's primary role in pathology consultation. James Ash, the curator during the war and a pathologist, noted, "Shortly after the last war, more concerted efforts were instituted to concentrate in the Army Medical Museum the significant pathologic material occurring in Army installations." He closed with the complaint, "We still suffer under the connotation museum, an institution still thought of by many as a repository for bottled monsters and medical curiosities. To be sure, we have such specimens. As is required by law, we maintain an exhibit open to the public, but in war time, at least, the museum per se is the least of our functions, and we like to be thought of as the Army Institute of Pathology, a designation recently authorized by the Surgeon General."
After the war, it evolved into the tri-service Armed Forces Institute of Pathology.