A flexible biopsy needle assembly includes a flexible coring stylet that is slidably disposed within a flexible outer cannula. The stylet includes an elongated body, a tip, a sampling notch adjacent to the tip, and at least one ferrule along the length of the body. The cannula includes an elongated tubular body defining a lumen sized for sliding passage of the stylet, a cutting edge at the opening of the lumen, and an array of slits along the length of its body. The slits are sized to allow the diameter of the ferrule(s) to extend partially therein. The slits and ferrule(s) interact to limit or control the flexibility of the cannula at the location of the slits.