Figure 4-21:

Mechanism of action of Tru-Cut biopsy needle for typical nodular biopsy. A small skin incision is made with a No. 11 blade to allow insertion of the instrument. A, With the instrument closed, the outer capsule is penetrated. B, The outer cannula is fixed in place, and the inner cannula with specimen notch is thrust into the tumor. Tissue then fills the notch. C, The inner cannula now is fixed while the outer cannula is moved forward to cut off the biopsy specimen. D, The entire instrument is removed. E, The inner cannula is pushed ahead to expose tissue in the specimen notch.

(From Withrow SJ, Lowes N: Biopsy techniques in small animal oncology, J Am Anim Hosp Assoc 14:899–902, 1981.)