Incidental Collision Tumor Two Common Metastases Meet in the NeckKallen, Michael E., MD; White, Rachel, MD; Hittman, Jamie, MD; Hatten, Kyle M., MD; Stashek, Kristen M., MD; Staats, Paul N., MD; Papadimitriou, John C., MD, PhDAJSP: Reviews & Reports: January/February 2019 - Volume 24 - Issue 1 - p 19–21 doi: 10.1097/PCR.0000000000000296 Case Reports Abstract Author InformationAuthors Article MetricsMetrics Human papillomavirus (HPV)–positive oropharyngeal squamous cell carcinoma is a biologically and clinically distinct type of head and neck cancer, featuring a generally improved prognosis over its HPV-negative counterparts. Papillary thyroid carcinoma is the most common thyroid malignancy and has a high frequency of regional lymph node metastasis and generally indolent clinical behavior. We present a case of intranodal collision between HPV-positive oropharyngeal squamous cell carcinoma and incidental papillary thyroid carcinoma. These two common lesions of the head and neck highlight an emergent area of complicated histology and raise interesting questions about tumor biology. We briefly review the variations of composite lesions described in the head and neck, as well as the potential prognostic implications between different types and role of ancillary testing and molecular diagnostics in their separation. Department of Pathology, University of Maryland School of Medicine, Baltimore, MD. Reprints: Michael E. Kallen, MD, Department of Pathology, University of Maryland School of Medicine, 22 S. Greene St, Baltimore, MD 21201. E-mail: firstname.lastname@example.org. The authors have no funding or conflicts to declare. © 2019 Lippincott Williams & Wilkins, Inc.