Frozen sections – A Primer

Frozen section is the main form of intraoperative consultation in which the surgeon sends tissue to the pathologist during the operation for rapid diagnosis in order to make immediate management decisions and to triage tissue for different studies. Other forms of intraoperative consultation include gross examination and smear preparations.  Most commonly, frozen section is used during oncological surgery or when tumor is suspected.

Due to the rapidity and nature of the freezing process, there are numerous artifacts that limit interpretation of the tissue, including lack of cellular or nuclear detail, tears or missing tissue, or ice crystals in certain tissues.  Therefore, frozen section is not a substitute for definitive diagnosis, and the expectations are lesser. The information provided to the surgeon may consist of:

  • just the adequacy of the specimen
  • whether the lesion is benign or malignant
  • the status of a margin
  • or the general category of tumor such as whether a neoplasm is carcinoma, whereby a surgeon may proceed with definitive surgery, or lymphoma in which additional surgery is suspended and the final classification rests upon further studies.

Nevertheless, frozen section diagnosis accuracy rates can be expected to be above 90%, except in certain cases, such as mucinous neoplasms of the ovary, in which reported rates are in the range of 60% due to inherent sampling issues. Frozen sections are distinguished from permanent sections, the latter of which are produced after extensive tissue processing (usually overnight) and are considered the gold standard of microscopy-based tissue evaluation.

The process begins with alerting the Pathology Gross Room of an impending frozen section and immediate delivery of the specimen by either OR personnel or the pneumatic tube system. The College of American Pathologists (CAP) turn-around-time guideline is 20 minutes from the time the specimen is received in the laboratory to the time the diagnosis is reported to the surgeon. The turn-around time for single, small biopsies is often faster than 20 minutes. However, in complex cases, when inking or dissection of the specimen is needed, when multiple sections are required, or when concurrent frozen sections are requested, the turn-around time can be longer than 20 minutes. The frozen section diagnosis is incorporated into the final surgical pathology report with resolution of any discrepancies.

Tips for successful Frozen Section consultation:

1)  Effective communication:  Clinicians should convey pertinent clinical history, especially prior cancer history, preoperative diagnoses, radiological findings, and precise anatomic location; they should also clarify the management algorithm when appropriate; finally, they should ask questions when the diagnosis is not clear or does not correlate with clinical impressions.

2) Sampling:  Unfixed (i.e. “fresh” and not in formalin) tissue should be sent. Bone or tissue with extensive calcifications cannot be frozen and cut, and fat is very difficult to cut. The pathologist may need additional tissue if the original sample is inadequate.

3) Unnecessary frozen sections, in which the diagnosis does not modify immediate intraoperative management, should NOT be requested, as it may compromise the pathologist’s ability to make a diagnosis on permanent sections.

4) Some frozen section diagnoses may need to be deferred.

5) Among pathologists, consultation with colleagues is encouraged.

6) Some requests for frozen section may not be honored, as in the case of melanoma, since the integrity of the tissue sample for final diagnosis is the paramount responsibility of the pathologist.

– Jeanette D. Cheng, M.D., Consulting Pathologist for the Anatomic Pathology Laboratory at PAH

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