Collision Lesions in Head and Neck Area: A Retrospective Study of 97 Reported Cases

Background: Collision (hybrid) lesions consist of two or more distinct histologic types occurring separately but within the same area. This review focuses on discussing all related and available case reports of hybrid lesions in the head and neck area. Methods: The literature was searched using several databases, including Scopus, Web of Science, PubMed, and Google Scholar. Papers published from 1990 to 2022 with full text available were considered for inclusion in the study. For a more comprehensive understanding, all lesions were categorized into cutaneous, jaw, and salivary gland groups and lesions in miscellaneous tissues. Results: In general, 97 reported collision lesions developed in the head and neck region. Among them, 31 (32%) and 34 (35%) cases were cutaneous hybrid lesions and in the jaws, respectively. In addition, 27 (27.8%) and 5 (5.1%) cases were in salivary glands and miscellaneous tissues, respectively. Conclusion: While the presence of true hybrid tumors is well-established, some reported cases have prompted researchers to categorize them as biphasic differentiations. The rarity of these cases contributes to limited knowledge regarding their clinical behavior, prognosis, and optimal treatment. It is crucial to emphasize the characteristic and potentially perplexing histological appearances.