What type of biopsy allows for a rapid preliminary diagnosis during surgery but is not 100% reliable?

The correct choice is a frozen section biopsy. This procedure is commonly performed during surgeries, allowing a rapid analysis of tissue samples while the patient is still undergoing the operation. Surgeons can make immediate decisions based on the preliminary results obtained from this technique, which can be pivotal in determining the extent of surgery needed, especially in cases like cancer, where clear margins are essential.

Frozen section biopsies are not 100% reliable primarily due to the limitations of the technique itself. The process involves freezing the tissue, which can introduce artifacts that may affect the interpretation of the sample. Additionally, the speed of the analysis means that there may not be enough time to adequately assess all features of the sample, and rarely, the initial diagnosis may differ from the final pathology report based on the processed (paraffin-embedded) tissue view.

In contrast, excisional biopsy, endoscopic biopsy, and incisional biopsy typically provide more definitive diagnoses because they involve the removal of larger samples or whole lesions, allowing for comprehensive examination under standard processing methods, which tend to yield more accurate results.