Section 2 -

Intraoperative Consultation in Mucosal Lesions of the Upper Aerodigestive Tract (UADT) Bruce M. Wenig Continuum Hospitals of New York

Indications Indications for intraoperative consultation (IOC) in mucosal (squamous cell) lesions of the UADT include: 1) render a histologic diagnosis (e.g., carcinoma/dysplasia) when definitive therapeutic intervention is planned immediately; 2) assessment of the adequacy of resection (i.e., surgical resection margins); 3) preliminary assessment of the nature of a planned procedure based on the extent and distribution of the neoplasm (e.g., subtotal versus total laryngectomy); 4) adequacy for diagnostic purposes; 5) determination for special handling (e.g., immuno-hisotochemistry, flow cytometry, microbiologic cultures, other); 6) determination of neurotropism, lymph-vascular space invasion (LVI) or bone involvement that may necessitate resection of the involved bone (e.g., mandibulectomy); 7) if lymph nodes are excised then a frozen section may be requested to exclude the presence of metastatic disease and the need for a neck dissection. Surgeon's Expectations The surgeon expects the pathologist: 1) to establish the diagnosis of carcinoma/dysplasia and differentiate it from look-alike lesions; 2) confirm presence of absence of lesional tissue at the margins of resection; 3) when applicable, identify the presence of osseous involvement; 4) when applicable, identify the presence of nodal metastasis. Specimen Handling and Orientation The evaluation of surgical margins of resection for the presence or absence of lesional tissue falls under the purview of the surgical pathologists. However, how the specimen is removed and the orientation of the specimen is the responsibility of the surgeon. Once removed and properly oriented, the specimen becomes the responsibility of the surgical pathologist. There is no standard method by which surgeons remove tissue and thereby request intraoperative consultation of the surgical resection margins. Some approaches include: excision of the entire lesion, designation of specific margins and tissue selection by the pathologist for frozen section; submission of biopsies from areas of clinical concern following the main resection and these biopsies are entirely submitted for frozen section. There are some centers in which all of the circumferential resection margins are submitted for frozen section irrespective of the number of frozen sections that may be required to completely evaluate the circumferential margins. In other centers, a limited number of frozen sections (e.g., up to four – anterior, posterior, medial and lateral) are submitted as determined by the pathologist. Right Angle (Perpendicular) versus Parallel (En-Face) Sections Right angle sections: Advantages - technically easier to obtain full thickness sections; distance of the lesion to the resection margin can be viewed and measured. Disadvantages - allows for evaluation of a relatively small area of the lesion/margin. Parallel sections: Advantages - allows for evaluation of a larger area of the lesion/margin to include an entire margin if necessary. Disadvantages - if the surgical margin is uninvolved the distance of the lesion to the resection margin cannot be viewed and/or measured; due to retraction from the underlying connective tissues the superficial layers (i.e., mucosa and submucosa) may not be optimally seen. Note: If parallel sections are made, the recommendation is to embed the tissue with the true surgical margin deepest in the block. Surgical Resection Margins Arguably, the most common request of the pathologist by the head and neck surgeon at the time of IOC is the assessment of the surgical margins. Successful local control of a malignant tumor depends on complete surgical excision of all the disease. The presence of gross residual cancer results in local persistence of disease and increased morbidity and mortality. Factors that impact on the assessment of the surgical margins include the type of surgical specimen, proper orientation of the specimen, proper sectioning of the specimen and obviously the correct interpretation of the histopathologic changes. Even in the best situations an intraoperative report of negative margins may be followed a few days later by a permanent section diagnosis of positive margins. The use of IOC will also allow the surgeon to extend the surgical resection without loss of orientation of the operative field, a potential problem when additional surgery is required in a second operation. Further, carcinoma remnants that have not been completely removed in the initial operation often are difficult to identify macroscopically, making their removal in a second operation more difficult. Errors in interpretation and in sampling accounted for discrepancies. Insufficient leveling of the frozen block may resulted in discrepancies. In examining mucosal margins for dysplasia/SCC, the frozen section tissue should be completely sampled by examining several levels at the time of frozen section. While the frozen section diagnosis of surgical margins are extremely accurate they are not entirely reliable in eliminating positive margins in the final diagnostic report. Definition of a "Positive" Margin Specimens in which no tumor or dysplasia is present at the surgical margins of resection, are considered as completely excised. "At the margin of resection" means that the neoplastic cells are seen in contact with or lie within millimeters of inked margin. In this situation, the specimen is considered incompletely excised, requiring a wider excision. Batsakis made a number of cogent recommendations including: 1) the sole reliance of margins as assessed on the resected specimen should be discouraged and, when feasible, the intraoperative evaluation of tissue surrounding the specimen should be made and have that regarded as the "true margin"; 2) the histologic definition of what constitutes a "positive" should be uniformly accepted and applied. There is discrepancy in the literature as to what constitutes a positive or negative resection margin. While some authors only include invasive carcinoma at the margin as positive excluding carcinoma in situ, dysplasia and gross residual disease, most pathologists would agree with the classification of positive margins, as defined by Loree and Strong: lesional tissue within 0.5 mm of the surgical margin (so-called close margins) with the exception of laryngeal lesions. Suffice to say that the evaluation of dysplasia under optimal circumstances can be subjective let alone at the time of frozen section where tissue distortion and artifact create additional diagnostic difficulties potentially resulting in misdiagnoses, including overdiagnosis and underdiagnosis. The diagnosis of severe dysplasia has equal biologic significance with carcinoma in situ and microinvasive carcinoma. A diagnosis of mild dysplasia is of questionable significance as the progression of low-grade dysplasia to higher grade epithelial lesions is so low as to make this diagnosis of little clinical significance, and often of minimal concern to the head and neck surgeon. However, the progression of moderate dysplasia to a higher grade lesion is nearly similar to that of severe dysplasia, so that a frozen section diagnosis of moderate dysplasia results in a therapeutic approach similar to that of severe dysplasia. Adequacy of Resection Margins The presence of lesional tissue within 5mm of the inked surgical margin irrespective of whether it is invasive carcinoma or carcinoma in situ/severe dysplasia places a patient at a nearly equal risk for local recurrence. These margins are associated with approximately 80% incidence of recurrent disease, so that failure of local control is not inevitable with such positive margins. The absence of positive margins does not guarantee local control of disease nor is it a reliable guide to the biologic behavior of a tumor. The question of how wide a tumor should be excised is the responsibility of the surgeon. However, for some specimens such as the laryngeal SCC, free margins up to 5 mm may be sufficient while a similar tumor at another extralaryngeal site, such as the oral cavity and pharynx (oro-, hypopharynx) wider margins (1.0 cm) are optimal. Factors Impacting of Margin Status and Prognosis The variability in "positive surgical margins" is dependent on multiple factors, not the least important of which may be the definition of what constitutes a positive margin. The factors that may impact on whether a margin is positive or negative, and in prognosis (control of disease) include: clinical stage; tumor size; pattern of invasion; adjuvant therapy; histopathologic evaluation; site dependency; soft tissue margins. Brandwein-Gentsler et al suggest that resection margin status alone is not an independent predictor of local recurrence nor should resection margin status alone be used as the sole variable in deciding whether adjunctive radiation therapy is required; rather the need to give adjunctive radiation is suggested to be based histologic assessement that results in stratification of patients into low-risk, intermediate-risk and high-risk categories that define recommendations for adjuvant radiotherapy (Table 1). Table 1. Risk Assessment for Oral Squamous Cell Carcinoma Histologic Variable 0 1 3 Perineural invasion None Small nerves Large nerves Lymphocytic response Continuous band Large patches Little to none Worst pattern of invasion at interface 1, 2 or 3 4 5 Risk Score* Risk for LR Overall Survival Probability Adjuvant Treatment with RT 0 Low Good No benefit 1 or 2 Intermediate Intermediate No benefit 3 - 9 High Poor Beneficial regardless of 5 mm margins ** = sum of all points; LR = Local recurrence; RT = Radiotherapy. Tissue Shrinkage and Surgical Margins Disparate surgical margin lengths of resected specimens between the in vivo measurements by the surgeon and the in vitro measurements by the pathologist have been reported for head and neck resection specimens. A mean tissue shrinkage of 31 to 46% may occur from the initial in-situ measurement by the surgeon to the final microscopic assessment of oral cavity and lingual surface mucosal margins by the pathologist. Histologic Prognostic Indicators Among the histologic findings that may impact on the prognosis in head and neck squamous cell carcinoma include: 1) status of the surgical resection margins, 2) tumor size, thickness and location of the lesion; 3) pattern of invasion; 4) involvement of lymph-vascular spaces, 5) invasion of soft tissue structures including nerves, bone and cartilage, 6) nodal metatsasis with or without extranodal extension of tumor; 7) distant metastasis; 8) host response; 9) neovascularization, and 10) presence of multiple malignancies. Pitfalls in the Intraoperative Assessment of Squamous Cell Carcinoma/Dysplasia On frozen section consultations of mucosal surface lesions, potential diagnostic pitfalls may include: reactive epithelial changes, postirradiation changes and Juxtaoral Organ of Chievitz. Contraindications Contraindications for the utilization of IOC on mucosal lesions include: 1) when the frozen section diagnosis will not have any impact on surgery or no immediate decision; 2) if the tissue specimen is small and additional sampling is not planned; 3) for heavily calcified or ossified tissue; 4) for certain lesions such as small cutaneous melanocytic lesions and lymphoproliferative lesions requiring special handling or extensive histologic evaluation for diagnosis. Intraoperative "Rapid" Immunohistochemical Assessment Intraoperative immunohistochemical assessment consisting of touch smear cytologic preparations and cytokeratin staining in 20 minutes from the time of tissue sampling. Limited studies to date on gastric mucosal margins in patients undergoing gastrectomy for gastric (non-signet ring cell) carcinomas show accurate and rapid assessment of tumor margins. To date, such analyses have not been published relative to mucosal margins of the UADT. Molecular Biology in the Assessment of Surgical Margins ("Molecular Margins") To date, there have been limited use of molecular biologic markers in assessing histopathologic negative surgical margins and negative lymph nodes for patients with HNSCC. The presence of p53 mutations in surgical margins and in lymph nodes negative for tumor by light microscopic examination portended a substantially higher risk of local recurrent disease than those patients without p53 mutations in their surgical specimens. Molecular biologic studies may augment conventional light microscopy in identifying cancer at surgical margins and in lymph nodes, and also may improve the prediction of local tumor recurrence. Accuracy In general, the accuracy of frozen section diagnosis in head and neck surgery is high, and when deferred diagnoses are excluded, the reported accuracy ranges from 97 to 99%. Potential discrepancies in the frozen section-to-permanent section diagnosis may include: sampling errors; interpretative errors; technical errors; communication errors. Lymph Nodes The frozen section diagnosis of lymph nodes is considered to be extremely accurate with an an accuracy rate of 98.9 percent, excluding deferred diagnoses, with a 0.1 percent false-positive rate and a 1 percent false negative rate. It should be noted that the lymph nodes represents the most frequently deferred specimen in frozen section diagnosis, especially in the diagnosis of a lymphoma. In general, the diagnosis of a carcinoma in a lymph node is not problematic at frozen section. Lymph node frozen section has also been utilized for accurate staging of the head and neck cancer patient. 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