Histological Pattern of Mandibular Invasion by Oral Squamous Cell Carcinoma

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Abstract
Objective:Mandibular invasion by oral squamous cell carcinoma may progress by either an infiltrative or an erosive histological pattern. The infiltrative pattern is marked by nests and cords of tumor cells along an irregular tumor front, and the erosive pattern exhibits a broad, pushing tumor front. The objectives of this study were 1) to define the characteristics associated with each histological pattern of mandibular invasion, 2) to assess the relationship between pattern of invasion and clinical outcome as measured by death with disease and disease presence at last follow‐up, and 3) to determine whether the cell cycle markers cyclin D1 and Ki‐67 are associated with the histological pattern of invasion or are predictive of outcome.Study Design:Retrospective study of 68 patients with mandibular invasion by oral cavity squamous cell carcinoma treated by mandibulectomy.Methods:The clinical records, pathology reports, and original H&E‐stained slides were reviewed for each patient. Immunohistochemical staining of cyclin D1 and Ki‐67 was performed on slides cut from the paraffin blocks of these patients' specimens.Results:The parameters found to be significantly associated with the infiltrative pattern of mandibular invasion included higher tumor grade, medullary space invasion, positive bone or soft tissue margins, history of previously failed treatment, and postoperative tumor recurrence. The infiltrative pattern had a positive bone margin rate of 47.6% and a primary site recurrence rate of 52.6%. In contrast, the erosive pattern had a positive bone margin rate of 4.9% and a primary site recurrence rate of 16.7%. The infiltrative pattern of invasion gave a fourfold increased risk of death with disease and disease presence at last follow‐up in univariate and multivariate analyses when compared with the erosive pattern of invasion. The 3‐year disease‐free survival was 30% for the infiltrative pattern and 73% for the erosive pattern. The median disease‐free survival was 1.5 years for the infiltrative pattern and 5.5 years for the erosive pattern. There was no correlation between cyclin D1 or Ki‐67 staining and invasion pattern or clinical outcome.Conclusions:The infiltrative pattern of mandibular invasion by oral squamous cell carcinoma is correlated with a significantly worse prognosis when compared with the erosive pattern of invasion. The infiltrative pattern clearly exhibits a more aggressive behavior with an increased likelihood of positive margins, recurrence, death with disease, and shorter disease‐free survival. We recommend that pathologists routinely comment on the histological pattern of invasion when reviewing oral squamous cell carcinoma with mandibular invasion.