Fixation

Ideally, specimens are submitted fresh to the laboratory to facilitate sampling for research and measurements as fixation results in considerable shrinkage (15-30% on average) and discrepancy between clinical and pathological dimensions, e.g., margins of tumour clearance. It also allows cleaning out of the specimen and either partial or total opening for pinning out and fixation. This avoids specimen distortion and ultimately allows dissection appropriate to the specimen and tumour type, e.g., the assessment of circumferential resection margins. Adequate fixation of a cleaned, opened specimen requires 36-48 hours immersion in formalin. Where it is normal practice to submit resection specimens to the laboratory already in fixative, the theatre staff should be instructed on how to partially open and clean out the specimen but to avoid transecting the tumour segment and compromising margin assessment.

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