Squamous cell carcinoma of the tongue: subtypes and morphological features affecting prognosis

Squamous cell carcinoma (SCC) is the most common histological type of mobile tongue carcinoma. The incidence of mobile tongue carcinoma is decreasing in some countries owing to decreasing exposure to risk factors, but it has been reported to be increasing in younger people. The majority of mobile tongue cancers are conventional SCCs. Pathological diagnosis of conventional SCC is relatively easy. However, mobile tongue SCCs involve several subtypes that have distinct pathological features and biological behaviors. Some subtypes are relatively rare, and the pathological subtype influences treatment decision-making. Therefore, the recognition of SCC subtypes is crucial for proper treatment. In this review, we summarize nine SCC subtypes, including conventional SCC and highlight their pathological characteristics. We also report some morphological factors, such as the pattern of invasion, budding, desmoplastic reaction, lymphovascular invasion, and perineural invasion, which could be predictive of prognosis. As some morphological factors are closely associated with prognosis, pathologists may need to evaluate additional factors in pathological reports of near features. In summary, we highlight the basic knowledge of mobile tongue SCC with an emphasis on pathological subtypes, morphological features, and their relationship. We provide information to further elucidate SCC in the oral region.