He was internationally recognized as an expert diagnostician with regard to tumors of the musculoskeletal system—especially the bones, but was also an experienced and skilled general surgical pathologist.

They were farmers who had little cash income; therefore, young David Jr.-- and his three brothers and sisters—learned frugality and the virtues of hard work from an early age.

The United States entered World War II during his Ancker pathology training experience, and Dahlin enlisted in the U.S. Army Air Corps (USAAC) in 1942.

He spent his first service year in the training command in Texas and North Carolina, and was then posted to Bari, Italy, as a medical officer in the 15th Air Force.

Hence, he switched his training emphasis to anatomic and clinical pathology, completing residency in 1948 and publishing his master's degree thesis (at the University of Minnesota) on systemic amyloidosis.

Rapidly, Dahlin became a skilled general surgical pathologist in the mold of Dockerty, but began to develop special expertise in neoplasms of the skeletal system.

Working with Mark Coventry, an orthopedic oncologist, Dahlin cataloged the clinical, radiographic, macroscopic, and histopathologic features of virtually all bone tumors in the Mayo archive.

[1] Dahlin’s opinion was sought internationally on a huge number of challenging bone tumor cases, not only for advice on pathologic interpretation but clinical management as well.