Extratumoral invasion: A unique phenomenon of aggressive recurrent oropharyngeal squamous cell carcinoma

Background: Oropharyngeal squamous carcinomas cause significant morbidity and mortality. Poor prognosticators include lymphovascular and perineural invasion. Extratumoral phenotypes of these histologic findings confer worse prognoses. Methods: We report eight cases of recurrent oropharyngeal cancer with diffuse extratumoral lymphovascular invasion (ELVI) or extratumoral perineural invasion (EPNI) and review the existing literature. Results: On salvage resection for recurrence following primary radiation or chemoradiation, six patients manifested ELVI and two showed EPNI. These patterns conferred difficulty with complete surgical clearance; final pathologic analysis demonstrated positive margins for all eight patients. The six patients with ELVI were p16+ and the two with EPNI were p16-. Currently, two patients are deceased and six patients are alive at an average follow-up of 17.4 months. Of the six living patients, 2 have a new recurrence and are in hospice while 4 have no evidence of disease. Conclusions: ELVI and EPNI have received little consideration in the literature as unique histopathologic features of oropharyngeal squamous carcinoma. We present the first series on these adverse extratumoral features in recurrent disease. We call attention to these unique histologic features in the setting of recurrent oropharyngeal cancer to encourage others to track the results of therapeutic intervention and to identify successful strategies for treatment.