Putting a Positive Spin on Inspections in the Mohs Surgery Histology Laboratory

In a College of American Pathologists (CAP)-certified Mohs surgery histology laboratory, inspections are conducted by a different pathologist every other year. Inspections are a nonpunitive process and educational exercise that provides the laboratory with improvement opportunities, so during an inspection, a positive attitude lowers the stress level. 

Mohs surgery histology laboratories share similar inspection preparation steps with every other histology laboratory, optimizing the inspection process. There are a few key exceptions highlighted in the steps below.

Preparing and remaining up-to-date is essential; playing "Catch-up" is always a mistake. To avoid that pitfall: 

• Go over the current CAP checklist with particular attention to the Summary of Changes sections, which lists all new, revised, or deleted/merged requirements. Address those as soon as possible, then go through the rest of the checklist, making sure all points are covered.
• In the year that an inspection is not occurring, use the interim checklist available. Note the changes that should happen and address them as soon as possible. The interim checklist is smaller than the checklist used for an inspection year and focuses on new, revised, or deleted/merged requirements. 
• Make sure to fill out QC logs daily, weekly, monthly per regulatory requirement. A good tip is to use a highlighter to designate the dates when there is no surgery, thus making review easier for the inspector. A footer on the log sheet explains the purpose of the highlighted sections. 
• Although not required by CAP, a tool to check the completion of a monthly review of expiration dates is helpful. 

During the laboratory inspection, inspectors want to see documentation of Mohs surgery cases. It is good to randomly pull the slides, diagram sheet, and operative note for 10 to 12 cases for review.

CAP requires a correlation of the number of blocks to the number of slides produced per layer (excision). (The current day's cases could be available for view if the inspector chooses, saving the technician the time of pulling the slides.) These are likely things the reviewer will check when reviewing documentation. Following this preparation process will help make the inspection process go more smoothly.

It is also a good idea to offer the inspector the opportunity to observe a Mohs surgery excision and follow the specimens through the entire process from excision to viewing the slide and diagram sheet with the Mohs Surgeon.

Unlike a non-Mohs histology laboratory, maintaining specimen identity throughout the entire process is challenging in the Mohs surgery histology laboratory. A Mohs specimen enters the laboratory in a labeled container matching the label on the accompanying diagram sheet. The specimen no longer has an identifier upon removing the sample from the container for embedding in the cryostat. So, using the accession number and the specimen number, a label can be created with an automatic label maker and embedded with the specimen to maintain its identity throughout the process.

CAP had made a strong recommendation to process all remaining tissue to retain it in the form of tissue blocks. When a patient needs Mohs surgery for skin cancer excision, the first thing completed is the diagnosis of cancer by a positive biopsy. The Mohs procedure is a secondary treatment modality, not a determinant of cancer. The entire surgical margin is visualized during the Mohs excision process, including the epidermal edge without gaps, and is a critical difference Mohs surgery has from regular histology practices.

The performance of Mohs surgery is the trimming of a single section of the underlayer of the frozen tissue block, so the reading pathologist can evaluate each section's margins to be sure it is clear of any tumor while the patient waits. In contrast, creating specimen-embedded paraffin blocks requires trimming to clear residual wax to reach the biopsy, eventually providing the diagnosis (positive or negative). A Mohs surgery specimen evaluates only the clarity of the margins of positively diagnosed tissue; therefore, paraffin embedding may create the risk of cutting into the block too deeply, providing margins containing the tumor. This workflow has the potential to be reported inaccurately as a false positive and is why this author's laboratory never processes the remaining tissue into a paraffin block.

On the newest checklist, the CAP recommendation changed from strongly recommending paraffin blocks to deferring to the judgment of the Mohs Surgeon to determine which blocks to save to paraffin for further studies. The Surgeon may decide to send a specimen to the pathology laboratory for more studies, such as IHC or Tumor Board.

The CAP requirement for specimen retention is two weeks from the day the case is signed out. On the day of surgery, when the Surgeon signs the diagram sheet (which serves as the laboratory report) to designate the case negative that signs out and closes the case, and two weeks from that date, the disposal of the case tissue occurs.

The CAP inspector can decide to give violations to a laboratory. The laboratory may disagree and dispute the violation but should do so in a manner that clearly states the reasons for the dispute. A discussion and understanding of the violation at the inspection time is good practice for minor infractions and possibly addressed before the inspector leaves the laboratory. The discussion documentation will help support the appeals process to the governing body.

In conclusion, staying current with updates and the CAP guidelines prepares the laboratory for inspection. Staying stress-free and positive during the inspection helps build rapport with the inspection team. Remain open and amenable to recommended changes. With the optimum outcome for the patient in mind, the path to and maintenance of a high standard of performance is to value the inspection process.

CAP provides a wealth of information that we utilize to maintain a high standard of laboratory performance.

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