Trocar Needles' Role in Reducing Tissue Core Loss And Crush Artifacts

The Key to Improving Pathological Diagnostic Quality

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The greatest hidden failure in core biopsy is tissue core loss (sample drop-out) and crush artifact, both of which frequently compel operators to increase core pass counts-directly contradicting "reducing core biopsy passes." The coaxial trocar system alleviates these problems in three ways:

First, the closed channel protects the sample. Traditional non-coaxial Tru-Cut requires independent skin-to-lesion penetration for each needle; during withdrawal, the sample notch often scrapes subcutaneous tissue, causing the core strip to detach or remain trapped in the notch and difficult to extract. After a coaxial trocar establishes the cannula, the biopsy needle moves entirely within the metal sheath; upon withdrawal, the outer sheath shields it from surrounding tissue contact, significantly improving the probability that the core strip remains completely intact in the sampling notch.

Second, it reduces sample contamination from hematoma caused by repeated punctures. Multiple penetrations of the same area easily cause needle track oozing; blood mixing into the sample dilutes cellular components or is misdiagnosed as hemorrhagic necrosis. The single-channel coaxial trocar allows subsequent samplings to avoid the already-bleeding segment of the needle track (by fine-tuning the cannula angle), yielding purer samples.

Third, it reduces crush artifacts. When the coaxial trocar cannula features electropolished inner walls (Ra ≤ 0.2 μm) and the biopsy needle notch is well-designed, the tissue core slides unobstructed into the fixation chamber without requiring forceful extraction with forceps-metal forceps squeezing is the primary cause of architectural destruction in glands and lymphoid tissue. It is recommended to rinse with saline or use fine nylon needles to tease out the core strip into the fixative.

Clinical evidence: In breast coaxial trocar + VAB systems, core strip integrity exceeds 95%; non-coaxial manual core biopsy achieves approximately 78%–85%. In small liver nodules, the ~6–7 percentage point improvement in diagnostic sensitivity with coaxial trocars is mainly attributed to improved sample quality rather than simply taking more samples.

Communication points for pathology departments: After establishing a trocar channel, operators are advised to note "coaxial single-channel multi-sampling" so pathologists recognize that slightly shorter second/third cores belong to different orientations of the same lesion rather than different cases. For procurement: prioritize trocar needles with EP-treated inner walls, sampling notch compatibility markings, and clearly stated fit clearance data.