NTRK1 and cancer: With the exception of several rare tumor types (e.g., secretory breast carcinoma, mammary analog secretory carcinoma, congenital fibrosarcomas, and congenital mesoblastic nephroma), the majority of the TRK fusions occur in low frequencies in a variety of common cancers over a diverse tissue/cell lineages (e.g., lung adenocarcinoma, sarcoma, acute myeloid leukemia, colorectal cancer) [6, 7] (Table 1).