Given the conundrum of focal and weak staining which can be detected with pan-TRK IHC and the established lower limit of positivity (i.e. positivity in at least 1% of the tumor cell population), knowledge of the incidence of NTRK fusions in the tumor subtypes may influence whether such staining is interpreted as non-specific or equivocal. The gene discussed is NTRK1; the disease is neoplasm.