Introduction: Oral squamous cell carcinoma often invades the mandible. The broad definitions of the erosive and infiltrative patterns of mandibular invasion have been described in the literature. However, a precise definition of what constitutes an erosive pattern of mandibular invasion has not been described and is certainly not agreed upon by pathologists across institutions. When squamous cell carcinoma of the oral cavity erodes cortical bone of the mandible, the language “abuts the mandible” is commonly utilized. This often creates ambiguity across pathologists and institutions regarding the presence bone invasion. This is important in both deciding on appropriate adjuvant therapy as well as comparing outcomes across institutions. The objective of this study is to propose a definition of erosive mandibular invasion through a pathologic review of false negative and false positive cases of mandibular invasion.
Methods: Series of 107 consecutive mandibulectomy cases for oral squamous cell carcinoma were retrospectively reviewed by a board-certified anatomic pathologist. For each case, the pathologist determined the presence/ absence of mandibular invasion, pattern of mandibular invasion, and presence/ absence of medullary space invasion. Early cortical invasion was defined as bone absorption deep to the periosteum. The accuracy of identifying bone invasion was determined by using the retrospective interpretation of bone invasion as the true interpretation, which was compared to the interpretation on the original pathology report. The association of the pattern of invasion with sensitivity of identifying mandibular invasion was examined.
Results: Sixty-nine percent (74/107) of cases were identified as having bone invasion, and 31% (33/107) of cases did not have bone invasion. Of the cases with mandibular invasion, 53% (39/74) exhibited the erosive pattern of invasion and 47% (35/74) exhibited the infiltrative pattern of invasion. Discrepancy between the original pathology report and the retrospective interpretation of the slides was found in 16% (17/107) of cases, indicating an accuracy of 84%. Amongst the 17 cases with discrepancy between the original pathology report, 71% (12/17) were false negative cases, and 29% (5/17) were false positive cases. The sensitivities for declaring mandibular invasion for the erosive and infiltrative patterns of invasion were 77% (30/39) and 91% (32/35), respectively (p=0.08).
Conclusions: The accuracy of declaring mandibular invasion in the original pathology report was 84% in this study. Fifty-three percent (9/17) of cases in which there was a discrepancy between the original pathology report and the retrospective interpretation were due to false negative erosive mandibular invasion cases. Although the differences in sensitivity of detecting mandibular invasion between the erosive and infiltrative patterns of invasion was not statistically significant in this study, this is certainly of clinical significance. These findings can likely be attributed to the lack of definition of the erosive pattern of invasion across pathologists. This study will present both a pictorial and written definition of erosive mandibular invasion with the hope of improving uniformity across institutions and pathologists.