Standard Operating Procedure for Tissue Processing

Standard Operating Procedure for Tissue Processing

This document outlines the standardized workflow for the fixation, dehydration, clearing, and infiltration of biological tissue samples. Adherence to these protocols is essential to ensure consistent morphological preservation and high-quality diagnostic outcomes.

1. Scope and Responsibility

• Scope: Applies to all histological tissue specimens received by the laboratory.
• Responsibility: [Department Name] laboratory personnel are responsible for the execution and documentation of these procedures.

2. Required Equipment and Reagents

• [List specific tissue processor model]
• [List specific fixative, e.g., 10% Neutral Buffered Formalin]
• [List specific alcohols and clearing agents]
• [List embedding media, e.g., Paraffin Wax]

3. Processing Workflow

1. Accessioning: Verify patient identification against the [Laboratory Information System] and ensure specimen containers are labeled with [Unique Identifier].
2. Fixation: Submerge tissue in [Fixative Name] for a minimum of [Number] hours, ensuring the volume ratio is at least 10:1.
3. Dehydration: Transfer tissue through a graded series of [Alcohol Type] to remove water.
4. Clearing: Immerse tissue in [Clearing Agent] to remove the dehydrating agent and prepare for infiltration.
5. Infiltration: Submerge tissue in molten [Paraffin Type] at [Temperature] °C to replace the clearing agent.
6. Embedding: Orient the tissue in a mold and fill with [Paraffin Type], ensuring proper alignment for microtomy.

4. Quality Control

• Verify that the tissue processor has completed the cycle without error logs.
• Inspect processed blocks for signs of under-processing (softness) or over-processing (brittleness).
• Document any deviations in the [Maintenance/Deviation Log].

Pro Tips

• Consistency: Always rotate reagents on a strict schedule based on the number of cassettes processed, not just the calendar date.
• Temperature Monitoring: Keep a daily log of the paraffin embedding center temperature to prevent heat-induced tissue damage.
• Orientation: Ensure that "en face" or "cross-section" requirements are clearly noted on the requisition form prior to embedding.

Completion and Approval

• Document owner: [Role or team]
• Prepared by: [Full name]
• Reviewed by: [Full name]
• Approved by: [Full name]
• Effective date: [Date]
• Next review date: [Date]
• Version: [Version number]
• Signature: ______________________
• Date signed: [Date]

FAQ

How often should reagents be changed?

Reagents should be changed based on the laboratory's validated throughput volume (e.g., every [Number] cassettes) or at least once every [Number] days, whichever comes first.

What should I do if the tissue processor alarms mid-cycle?

Immediately document the error code, assess the status of the tissue, and consult the [Emergency Protocol Manual] to determine if the tissue requires manual reprocessing or can be resumed.

How do I handle fatty tissue during processing?

Fatty tissues require extended clearing times and lower processing temperatures to ensure complete infiltration without damaging the cellular architecture.