Introduction

Adequate surgical margins represent the critical determinant of recurrence rates and long-term outcome in oral epithelial dysplasia and squamous cell carcinoma management. Unlike benign odontogenic lesions where simple enucleation suffices, epithelial pathology requires definition of specific margin dimensions, incorporation of normal tissue beyond the visible lesion, and histopathological assessment to confirm adequacy. This review addresses the definition of surgical margins, margin dimensions for specific pathologies, intraoperative assessment techniques, frozen section histopathology protocols, Mohs micrographic surgery adaptation to oral regions, specimen orientation documentation, and management of inadequate margins.

Surgical Margin Definitions

Surgical margins are classified into three categories based on histopathological assessment: (1) clear margins represent absence of neoplastic or dysplastic cells at the inked peripheral border and deep margin of the specimen (gold standard, 2-5% recurrence rates depending on tumor stage); (2) close margins represent dysplastic or neoplastic cells within 2-5 mm of the inked margin (5-15% recurrence rates, requiring close surveillance and consideration of adjuvant radiation); and (3) involved margins represent dysplastic/neoplastic cells at the inked margin (20-50% recurrence rates, mandate re-excision or adjuvant therapy).

Margin dimension standards for oral squamous cell carcinoma historically utilized 1 cm (10 mm) peripheral margins and 5 mm deep margins based on early studies. Contemporary evidence suggests more nuanced requirements: (1) for T1-T2 tumors without perineural invasion (PNI), margins β‰₯3-5 mm deep provide equivalent recurrence rates to 10 mm margins (approximately 5-10% local recurrence); (2) for tumors with PNI, deeper invasion, or high-grade histology, margins β‰₯8-10 mm deep are justified (recurrence rates 8-15%); (3) peripheral margins β‰₯5-10 mm are generally adequate (less critical than depth for epithelial malignancies).

For oral epithelial dysplasia (without invasive carcinoma), margin requirements vary by dysplasia grade: (1) mild dysplasia can be managed with 2-3 mm margins and close surveillance; (2) moderate dysplasia requires 4-5 mm margins with 1-2 mm deep margins; (3) severe dysplasia/carcinoma in situ requires 5-8 mm margins and should be treated equivalently to invasive tumors.

Intraoperative Margin Assessment Techniques

Visual assessment identifies clinically obvious lesion extent and defines primary excision margins; however, microscopic invasion typically extends beyond visible borders by 2-5 mm. Therefore, clinical assessment alone is insufficient and must be supplemented by additional techniques. Toluidine blue staining identifies areas of dysplasia/malignancy with >85% accuracy in research settings, though lower sensitivity in clinical practice. Application: (1) rinse site with 1% acetic acid (2-3 seconds), (2) apply toluidine blue solution (1% buffered with acetic acid) to the site (1 minute contact), (3) rinse with 1% acetic acid, and (4) identify blue-staining areas indicating dysplasia. Toluidine blue staining typically extends beyond visible lesion margins by 1-3 mm, providing guidance for excision borders. False positives occur with inflammation or infection (10-15% of cases); confirmation with histopathology is mandatory. Vital dyes (methylene blue, tolonium chloride) similarly identify dysplastic areas but require similar confirmation. These techniques are more useful in identifying multifocal disease than in defining precise margins. Brush biopsy/cytology of the lesion margin and surrounding clinically normal tissue (5-10 mm from the lesion edge) can identify occult dysplasia beyond the gross lesion. Positive cytology in clinically normal-appearing tissue indicates need for wider margins. However, brush cytology demonstrates false negatives (20-30%) and should not replace histopathological assessment. Optical techniques including reflectance confocal microscopy (RCM) can visualize cellular morphology at the margins without excising tissue, enabling real-time assessment of margin adequacy. RCM is not yet standard clinical practice but demonstrates promise for intraoperative guidance.

Frozen Section Histopathology Protocol

Frozen section examination provides real-time histopathological assessment of margins during surgery, enabling re-excision if margins are inadequate. Specimen preparation requires: (1) identification of all margins with inking (typically using different colored inks for peripheral, deep, and specific anatomical borders), (2) orientation of specimen to preserve anatomical information, and (3) communication with pathology regarding critical margins requiring frozen section evaluation.

Margin marking technique: Orient the specimen with inked surfaces facing outward (prevents ink artifact on cut surface). Mark deep margin differently from peripheral margin (e.g., black ink for deep, red for peripheral, blue for medial); specify the anatomical location (e.g., "deep marginβ€”closest to mandible"). Frozen section interpretation: Pathologist assesses each margin for presence of dysplasia or carcinoma at the inked edge. Time requirement is typically 10-15 minutes for interpretation. Limitations of frozen section include: (1) less detailed cytopathology compared to permanent sections (frozen sections are ~25-50 micrometers thick vs. 5-10 micrometers for permanent; discordance rate 5-10%), (2) tissue artifact from freezing process, (3) inability to assess some special stains (immunohistochemistry not performed on frozen sections), and (4) sampling error (only a portion of the large margin surface is examined, potentially missing dysplasia in unsampled regions). Re-excision protocol: If frozen section reveals dysplasia/carcinoma at the margin, additional tissue is removed in the direction of the involved margin (typically 5 mm additional tissue). The additional specimen is re-oriented to clearly mark which edge was originally involved. This re-excision can be repeated multiple times until margins clear histopathologically. Some surgeons prefer a single generous re-excision (10-15 mm beyond initial margins) rather than sequential small re-excisions, balancing margin adequacy against morbidity from large defects.

Mohs Micrographic Surgery Adapted to Oral Regions

Mohs micrographic surgery (MMS) represents the gold standard margin assessment technique, examining virtually 100% of the surgical margin (vs. frozen section, which samples <5% of margin in typical specimens). MMS involves: (1) removal of thin tissue layers (0.5-1.0 mm), (2) complete processing and histological examination of all margins from each layer, and (3) re-excision only from areas where dysplasia/malignancy is identified, resulting in maximized tissue preservation while ensuring clear margins.

Adaptation to oral sites: While Mohs technique was developed for cutaneous lesions, adaptation to oral intramucosal sites is feasible and increasingly practiced. Oral Mohs has been applied to: buccal mucosa lesions, hard palate lesions, and anterior tongue lesions (more difficult due to mobile tissue and need for oral specimen orientation without external reference points). Technique: (1) initial excision removes the bulk of the lesion with estimated clear margins, (2) specimen is oriented on a numbered map, (3) the margin (not the entire lesion) is re-examined via Mohs-style processing, (4) thin (0.5 mm) sections are taken from the margins, and (5) re-excision is performed only from positive margin regions. Advantages include: near-zero recurrence rates (0-2% for oral SCC, vs. 10-25% for conventional excision), maximized tissue preservation (critical for oral cavity anatomy), and detection of multifocal disease. Disadvantages: (1) increased operating time (typically 3-4 hours for simple lesions), (2) requires specialized training and dedicated pathology support, (3) increased cost ($2,000-5,000 vs. standard excision $500-1,500), and (4) not available at all institutions. Candidates for Mohs in oral sites include: lesions in cosmetically/functionally critical areas (anterior tongue, soft palate), patients with aggressive histology, and tumors with perineural invasion.

Specimen Orientation and Documentation

Orientation marking is essential for pathologist interpretation and potential re-excision planning. Use a systematic approach: (1) place the specimen on a standard surgical setup (place lateral borders "left" and "right" corresponding to patient anatomy), (2) use sutures to mark specific anatomical boundaries (e.g., suture at anterior border with 1 knot, posterior border with 2 knots), (3) photograph the specimen before inking, and (4) ink all margins with specified colors for different anatomical locations. Documentation requirements: (1) gross specimen description: size (e.g., 1.5 cm Γ— 2 cm Γ— 0.8 cm), color (e.g., red/white nodular, or hyperkeratotic white with erythematous base), and visible extent; (2) margin notation: specify which surfaces are deep, peripheral, and specific anatomical borders; (3) pathology request: specify if dysplasia is suspected, request frozen section assessment of margins, and note if patient is high-risk; (4) operative report diagram: sketch the lesion location and specimen orientation for pathology.

Management of Inadequate Margins

Discovery of dysplasia/carcinoma at histopathological margins on permanent section examination (24-48 hours post-surgery) requires: (1) prompt notification to the patient, (2) assessment of re-excision feasibility based on wound healing status (typically feasible within 1-2 weeks), and (3) discussion of options: (a) re-excision to achieve clear margins, (b) radiation therapy (if re-excision is not feasible due to extensive morbidity or patient refusal), or (c) close surveillance with serial examination and potentially imaging to detect early recurrence.

Re-excision planning: Specific anatomical location of margin involvement should be identified from the pathology report. The re-excision should include the involved region plus 5-8 mm of additional tissue in the direction of involvement. Ideally, re-excision margins are frozen sectioned to confirm clearance before closure.

Dysplasia Management Specifics

Oral epithelial dysplasia (OED) represents a spectrum from mild (low malignant potential, 0.5-5% malignant transformation rate per year) to severe (high malignant potential, 15-50% malignant transformation rate per year). Margin requirements and management decisions should consider: (1) dysplasia grade (mild vs. moderate vs. severe), (2) size and accessibility, (3) patient age and ability to comply with surveillance, and (4) esthetic/functional morbidity from excision.

Mild-moderate dysplasia in accessible locations can often be managed with laser ablation or simple excision with 2-3 mm margins plus close surveillance (examination every 3 months). Severe dysplasia should be managed more aggressively with excision incorporating 5-8 mm margins similar to invasive carcinoma protocols.

Conclusion

Surgical margins represent the most critical determinant of recurrence in epithelial pathology management. Systematic margin assessment using frozen section histopathology, adjunctive techniques including toluidine blue and brush biopsy, and consideration of Mohs micrographic surgery for selected oral sites optimize outcomes. Meticulous specimen orientation, documentation of anatomical landmarks, and clear communication with the pathology service ensure accurate margin assessment and enable appropriate re-excision when margins are inadequate. Recognition that microscopic invasion extends beyond clinical visibility, combined with systematic margin sampling and histopathological assessment, enables clinicians to achieve clear margins that minimize recurrence while preserving oral function and esthetics.