Surgical Pathology Levels Are Determined By

Surgical pathology levels, often referred to as "levels" or "step sections," are a crucial aspect of histopathological examination, particularly in the context of dermatopathology and the assessment of surgical margins. The determination of how many levels to examine, and at what intervals, is a complex decision-making process guided by a combination of factors, including the clinical context, the nature of the lesion, established guidelines, and the pathologist's judgment.

Understanding Surgical Pathology Levels

Surgical pathology involves the microscopic examination of tissue samples obtained during surgery. This examination is performed to diagnose diseases, assess the extent of disease, and evaluate whether surgical interventions have successfully removed all diseased tissue. One of the key challenges in surgical pathology is to ensure that the entire lesion of interest is adequately sampled and examined, particularly when dealing with conditions like skin cancer where complete removal is critical to prevent recurrence.

What Are Surgical Pathology Levels?

Surgical pathology levels refer to the process of serially sectioning a tissue block and examining multiple sections under a microscope. After a tissue sample is processed and embedded in paraffin, it forms a block. Instead of examining just one section from this block, the pathologist may request that the histotechnologist cut multiple sections at different depths within the block. These sections are then stained and mounted on slides for microscopic evaluation.

The term "levels" can be slightly misleading, as it doesn't always refer to equally spaced intervals. The pathologist can request sections at specific depths or intervals based on the characteristics of the tissue.

Why Are Levels Necessary?

Levels are necessary for several reasons:

• To Detect Subclinical Disease: Some diseases, like certain types of skin cancer, may not be visible on the surface of the tissue. Examining deeper levels can reveal nests of tumor cells that would otherwise be missed.
• To Assess Surgical Margins: Surgical margins are the edges of the tissue removed during surgery. Evaluating these margins is crucial to determine if the entire lesion has been excised. Levels allow for a more thorough assessment of the margins, ensuring that no tumor cells extend to the edge of the resected tissue.
• To Identify Subtle Features: In some cases, the diagnostic features of a disease may be subtle or only present in certain areas of the tissue. Examining multiple levels increases the likelihood of identifying these features.
• To Reconstruct the Lesion: By examining serial sections, the pathologist can mentally reconstruct the three-dimensional structure of the lesion, which can be helpful in understanding its growth patterns and behavior.

Factors Determining Surgical Pathology Levels

The determination of how many levels to examine is not arbitrary. It is based on a careful consideration of several factors:

1. Clinical Context

The clinical history and presentation of the patient play a crucial role in determining the approach to sectioning.

• Type of Lesion: Different types of lesions have different propensities for recurrence and different patterns of growth. For example, a deeply invasive melanoma requires a more thorough margin assessment than a superficial basal cell carcinoma.
• Location of Lesion: The location of the lesion can also influence the decision. Lesions in high-risk areas, such as the face or near critical structures, may require more extensive margin control.
• Previous Treatment: If the lesion has been previously treated with surgery, radiation, or other therapies, it may be more difficult to assess, and more levels may be necessary.
• Immunocompromised Status: Patients who are immunocompromised may have a higher risk of aggressive disease, and a more thorough examination may be warranted.

2. Pathological Characteristics of the Lesion

The microscopic features of the lesion itself are a critical determinant of how many levels are needed.

• Tumor Type: Different types of tumors have different growth patterns and risks of recurrence. For example, aggressive tumors like squamous cell carcinoma may require more extensive margin assessment than benign lesions.
• Tumor Grade: The grade of a tumor reflects its degree of differentiation and aggressiveness. Higher-grade tumors typically require more thorough margin assessment.
• Tumor Size: Larger tumors generally require more levels to ensure adequate margin assessment.
• Tumor Depth: The depth of invasion of a tumor is a key prognostic factor. Deeper tumors require more careful margin assessment.
• Margin Status on Initial Sections: If the initial sections show tumor cells approaching the surgical margins, the pathologist will typically request additional levels to determine if the margins are truly clear.
• Presence of Perineural or Lymphovascular Invasion: The presence of tumor cells invading nerves or blood vessels indicates a higher risk of recurrence and may warrant more extensive margin assessment.

3. Established Guidelines and Protocols

Various professional organizations have published guidelines and protocols for the examination of specific types of lesions. These guidelines often include recommendations for the number of levels to examine and the intervals between sections.

• American Academy of Dermatology (AAD): The AAD has published guidelines for the management of various skin cancers, including recommendations for margin assessment.
• National Comprehensive Cancer Network (NCCN): The NCCN also provides guidelines for the management of various cancers, including skin cancers, which may include recommendations for surgical pathology.
• College of American Pathologists (CAP): The CAP provides accreditation for pathology laboratories and has developed checklists and standards for various types of pathology specimens, including surgical pathology specimens.

These guidelines are not always prescriptive, and the pathologist must still exercise their judgment based on the individual case. However, they provide a framework for ensuring that specimens are adequately examined.

4. Pathologist's Judgment and Experience

Ultimately, the decision of how many levels to examine rests on the pathologist's judgment and experience. Pathologists are trained to recognize subtle features and patterns that may indicate the need for more thorough examination.

• Pattern Recognition: Experienced pathologists can recognize patterns of growth and invasion that may not be obvious to less experienced observers.
• Correlation with Clinical Findings: Pathologists must correlate their microscopic findings with the clinical history and presentation of the patient.
• Awareness of Pitfalls: Pathologists are aware of potential pitfalls in the interpretation of surgical pathology specimens, such as artifacts or variations in staining, and can adjust their approach accordingly.
• Consultation with Colleagues: In complex cases, pathologists may consult with colleagues to obtain additional opinions and insights.

5. Laboratory Resources and Efficiency

While patient care is the primary concern, laboratory resources and efficiency also play a role in the decision-making process.

• Turnaround Time: Examining multiple levels can increase the turnaround time for a case, which may be a concern for patients and clinicians.
• Cost: Each additional level adds to the cost of the examination.
• Availability of Resources: The laboratory must have the staff and equipment necessary to process and examine the additional sections.

The pathologist must balance the need for thorough examination with the need for timely and cost-effective service.

Common Approaches to Determining Surgical Pathology Levels

While the specific approach to determining surgical pathology levels varies depending on the factors discussed above, there are some common strategies that are used in practice.

1. Step Sections

Step sections involve cutting sections at regular intervals throughout the tissue block. For example, the pathologist may request sections every 50 micrometers. This approach is commonly used for assessing surgical margins, particularly in cases where the tumor is close to the margin.

2. Shave Sections

Shave sections involve cutting a thin layer off the entire surface of the tissue block. This approach is often used for assessing the margins of skin excisions. The entire perimeter of the excision is examined in a single section.

3. Targeted Sections

Targeted sections involve cutting sections from specific areas of the tissue block that are of particular interest. For example, if the pathologist sees tumor cells near the margin on one section, they may request additional sections from that area to determine if the margin is truly involved.

4. Complete Serial Sections

In some cases, the pathologist may request complete serial sections, where the entire tissue block is sectioned and examined. This approach is typically reserved for very small specimens or for cases where a thorough examination is critical.

Examples of Level Determination in Specific Scenarios

To illustrate how these factors come into play, let's consider some specific scenarios:

Scenario 1: Basal Cell Carcinoma on the Trunk

A patient presents with a small (5 mm) nodular basal cell carcinoma on the trunk. The dermatologist excises the lesion with a 4 mm clinical margin.

• Clinical Context: Basal cell carcinoma is a common, slow-growing skin cancer with a low risk of metastasis. Lesions on the trunk are generally considered low-risk.
• Pathological Characteristics: If the initial sections show a well-defined tumor with clear margins, the pathologist may not need to request additional levels. However, if the tumor appears aggressive or the margins are close, step sections may be necessary.
• Established Guidelines: Guidelines for basal cell carcinoma typically recommend adequate margin control, but do not always specify the number of levels.
• Pathologist's Judgment: The pathologist will assess the overall risk of recurrence based on the clinical and pathological findings and determine if additional levels are necessary.

Scenario 2: Squamous Cell Carcinoma on the Ear

A patient presents with a 1 cm squamous cell carcinoma on the ear. The dermatologist excises the lesion with a 5 mm clinical margin.

• Clinical Context: Squamous cell carcinoma is a more aggressive skin cancer than basal cell carcinoma, with a higher risk of metastasis. Lesions on the ear are considered high-risk due to their location and the potential for local recurrence.
• Pathological Characteristics: Squamous cell carcinoma is often more infiltrative and less well-defined than basal cell carcinoma. The pathologist will typically request step sections to ensure adequate margin control. The presence of perineural invasion or lymphovascular invasion would further increase the need for thorough margin assessment.
• Established Guidelines: Guidelines for squamous cell carcinoma often recommend more aggressive margin control than for basal cell carcinoma, particularly for high-risk lesions.
• Pathologist's Judgment: The pathologist will consider the clinical and pathological features of the lesion and determine the appropriate number of levels to ensure complete excision.

Scenario 3: Melanoma In Situ on the Face

A patient presents with a melanoma in situ (a very early form of melanoma) on the face. The dermatologist excises the lesion with a 5 mm clinical margin.

• Clinical Context: Melanoma in situ is a non-invasive form of melanoma that is typically curable with complete excision. However, lesions on the face are considered high-risk due to cosmetic concerns and the potential for recurrence.
• Pathological Characteristics: Melanoma in situ can be difficult to assess at the margins, as the atypical melanocytes may be subtle. The pathologist may request shave sections or step sections to ensure adequate margin control.
• Established Guidelines: Guidelines for melanoma in situ recommend complete excision with clear margins.
• Pathologist's Judgment: The pathologist will carefully examine the margins and request additional levels if necessary to ensure complete removal of the atypical melanocytes.

The Role of Technology in Determining Surgical Pathology Levels

Advancements in technology are also impacting the way surgical pathology levels are determined.

1. Digital Pathology

Digital pathology involves scanning glass slides to create high-resolution digital images that can be viewed and analyzed on a computer. This technology allows pathologists to easily review and share cases, as well as to use image analysis tools to quantify features and identify areas of interest.

Digital pathology can be used to guide the selection of levels by allowing the pathologist to quickly review the entire specimen and identify areas that require further examination. It can also be used to create virtual levels by digitally sectioning the tissue block.

2. Artificial Intelligence (AI)

Artificial intelligence (AI) is being developed to assist pathologists in various tasks, including the identification of tumor cells and the assessment of surgical margins. AI algorithms can be trained to recognize patterns and features that may be missed by the human eye.

AI can be used to prioritize cases for review and to highlight areas of interest that may require further examination. It can also be used to automate the process of margin assessment, reducing the workload for pathologists and improving the accuracy of diagnoses.

3. Three-Dimensional (3D) Reconstruction

Three-dimensional (3D) reconstruction involves creating a 3D model of the tissue block from serial sections. This technology allows pathologists to visualize the entire lesion in three dimensions, which can be helpful in understanding its growth patterns and behavior.

3D reconstruction can be used to guide the selection of levels by allowing the pathologist to identify areas that are poorly sampled or that require further examination. It can also be used to improve the accuracy of margin assessment by providing a more complete view of the surgical margins.

Challenges and Future Directions

Despite the advancements in technology and the development of guidelines, there are still challenges in determining surgical pathology levels.

1. Inter-Observer Variability

There can be significant inter-observer variability in the interpretation of surgical pathology specimens, particularly in the assessment of surgical margins. This variability can lead to inconsistencies in the number of levels examined and the final diagnosis.

2. Lack of Standardization

There is a lack of standardization in the way surgical pathology levels are determined. Different laboratories may use different protocols and guidelines, which can make it difficult to compare results across institutions.

3. Cost and Efficiency

Examining multiple levels can be costly and time-consuming, which can be a barrier to optimal patient care.

Future directions in this field include:

• Developing more standardized guidelines and protocols for determining surgical pathology levels.
• Using technology to improve the accuracy and efficiency of margin assessment.
• Developing AI algorithms to assist pathologists in the identification of tumor cells and the assessment of surgical margins.
• Conducting more research to determine the optimal number of levels to examine for different types of lesions.
• Implementing quality control measures to reduce inter-observer variability.

Conclusion

The determination of surgical pathology levels is a complex decision-making process that is guided by a combination of factors, including the clinical context, the pathological characteristics of the lesion, established guidelines, and the pathologist's judgment. While there is no one-size-fits-all approach, the goal is always to ensure that the specimen is adequately examined to provide the most accurate diagnosis and to guide treatment decisions. As technology advances and more research is conducted, the process of determining surgical pathology levels will continue to evolve, ultimately leading to improved patient outcomes. The key is to approach each case thoughtfully, considering all relevant factors, and to utilize the available resources to provide the best possible care.