However, when ETV6–NTRK3 fusion is expected (e.g., in mammary gland secretory carcinoma, salivary gland secretory carcinoma, and infantile fibrosarcoma), NTRK3 alone needs to be examined and only a single test is required for the examination, the use of FISH is appropriate. Here, NTRK3 is linked to congenital fibrosarcoma.