is a specific kind of: medical specialist, specialist.

is a broader term that covers: aetiologist, etiologist.

instances of which are: Florey, Howard Florey, Sir Howard Walter Florey | Karl Landsteiner, Landsteiner | Paget, Sir James Paget | Francis Peyton Rous, Peyton Rous, Rous | Rudolf Karl Virchow, Rudolf Virchow, Virchow.

derivation: diagnostics, nosology | pathology | pathology.