# Frozen Section Pathology > Frozen section pathology for NEET-PG Pathology: cryostat technique, margin and transplant indications, parathyroid fat stain, freezing artefacts and why melanomas are excluded. - Canonical URL: https://prepelephant.com/topics/neet-pg/pathology/frozen-section-pathology - Exam / course: NEET-PG · Subject: Pathology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Frozen Section Pathology", PrepElephant, https://prepelephant.com/topics/neet-pg/pathology/frozen-section-pathology ## Direct answer The surgeon waits, the patient is asleep, and the pathologist has roughly twenty minutes: frozen section is intraoperative consultation in which tissue is embedded in mounting medium, rapidly frozen in a cryostat at about minus 20 to minus 30 degrees Celsius, sectioned, stained with rapid haematoxylin-eosin and reported while the wound is still open. Its legitimate indications are margin assessment in breast-conserving and head-and-neck cancer surgery, determining the nature of an unexpected lesion, checking lymph nodes before committing to a nodal dissection, and identifying parathyroid tissue — with the oil-red-O fat stain on frozen tissue distinguishing lipid-poor adenoma from fat-rich normal gland. Melanoma margins, tiny lesions and most lymphoma workups are explicitly excluded, because freezing artefact sacrifices diagnostic quality on tissue that permanent sections need intact. ## What you must remember - **The pipeline:** specimen received fresh (never formalin-fixed), bisected and sampled at the face nearest the inked margin, embedded in optimum cutting temperature medium, cryostat-sectioned at 5-7 micrometres, rapid H&E, report to the theatre by phone. - **Classic indications:** resection-margin status, identification of an unexpected lesion, nodal assessment before a planned dissection, and confirmation of parathyroid tissue during neck exploration. - **Parathyroid trick:** frozen-section oil-red-O stain shows abundant intracytoplasmic fat in normal parathyroid and its loss in adenoma; combined with intraoperative parathyroid hormone kinetics, this settles neck re-explorations. - **Formal exclusions:** suspected lymphoma (flow cytometry and architecture need fresh and well-fixed tissue), melanoma margins (bread-loafed permanents judge them better), lesions so small that freezing consumes the diagnostic material. - **Artefact catalogue:** ice-crystal vacuoles in slow-frozen tissue, torn and folded sections, lost nuclear detail, and inability to cut heavily calcified or fatty tissue cleanly. - **Performance reality:** agreement with permanents runs in the mid-ninety per cent range in experienced hands, with a deferral rate that honest laboratories track rather than hide. ## A margin call during breast conservation The specimen arrives with a suture marking the superior aspect; the pathologist orients it, inks six faces in different colours, palpates the tumour and samples the closest cavity margin with a thin shave. While the cryostat head chills, the tissue is embedded with the true margin face-up so the first section reads the actual edge. The frozen slide shows ductal carcinoma in situ reaching within one millimetre of the sampled face — a positive/close call phoned to the surgeon, who extends the excision before closing. The remaining specimen goes for permanent sections, where final margins are confirmed; frozen assessment here is triage, not verdict. The same discipline governs a glioma resection, where the neurosurgeon samples tissue that looks or feels abnormal and the frozen answer — glioblastoma versus radiation necrosis — changes the operation in real time; squash preparation cytology is the neurosurgical companion technique. ## Where candidates slip Two misconceptions recur. The first is that frozen section exists to give a definitive grade — it does not; freezing distorts nuclear detail, artefactually inflates apparent atypia, and the technique answers bounded questions (margin involved or not, node involved or not, parathyroid or not). The second is forgetting that tissue consumed by freezing is tissue lost: a three-millimetre lesion frozen in its entirety may leave nothing for permanents, immunohistochemistry or molecular studies, which is exactly why tiny lesions and melanomas are deferred. Candidates also underplay the deferral — reporting "deferred for permanent sections" on ambiguous frozen morphology is correct professional conduct, not failure, and exam answers should say so. ## Frequently asked questions ### At what temperature does a cryostat operate? Roughly minus 20 to minus 30 degrees Celsius, adjusted upward for fatty tissue and downward for watery or soft tissue to obtain clean sections. ### Which lesion types should not be submitted for frozen section? Suspected lymphomas, melanoma margin assessment and minute lesions whose diagnostic material freezing would destroy — they demand permanent, well-fixed sections. ### How is parathyroid tissue identified intraoperatively? Frozen section with oil-red-O fat staining (fat-rich normal gland versus fat-poor adenoma or hyperplasia), corroborated by intraoperative parathyroid hormone half-life kinetics. ### What freezing artefacts mislead interpretation? Ice-crystal vacuoles, uneven section thickness, nuclear smearing and folds that mimic or obscure atypia, and the near-impossibility of sectioning calcified tissue cleanly. ### What is the role of frozen section in transplant surgery? Rapid assessment of an unexpected finding in a donor organ — such as a small cortical nodule in a donor kidney — to confirm the organ is safe to implant. ### Why is a deferred frozen-section report acceptable? Freezing artefact may render a confident diagnosis impossible, and deferring to permanent sections preserves accuracy — an audited, legitimate practice rather than a failure.