The instrument for sample tissue specimens comprises an inner shaft extending eccentrically through a distally closed outer shaft and intended for reception of an optical system comprising a lateral objective, which inner shaft is distally connected or connectible to a cutting edge which cooperates with an edge of a distal lateral viewing and cutting aperture in the outer shaft acting as a mating cutting edge over the area of this distal lateral aperture by axial displacement of the inner shaft within the outer shaft.