Clinicopathological evaluation of carcinoma cuniculatum: a variant of oral squamous cell carcinoma.

Carcinoma cuniculatum (CC) is a rare neoplasm of oral squamous cell carcinoma (OSCC) and remains a histopathological challenge to pathologists because of its low incidence and unique architecture. Therefore, the purpose of this study was to illustrate the clinicopathological findings and biological behavior about this distinctive lesion. Clinical and follow-up information were retrieved from medical charts, and histopathological analyses were performed. Our series included 15 cases of CC, and the study included seven men and eight women, age 44-92. The tongue and mandible were the most frequently affected sites. There were three lymph node metastasis cases, and three local recurrences; one of the patients died of lung metastasis from oral CC. Histopathologically, the point of differential diagnosis with other subtypes of OSCC included unique, cuniculatum architecture and branching crypts. Because of its well-differentiated status, the prognosis of CC is usually optimistic. However, recurrent cases in our study might have possessed invasive biological characters that were not well controlled by conventional treatment; in one case, a portion of the CC transformed into conventional squamous cell carcinoma (SCC). This might suggest that transformed CC rather than primary CC should be further emphasized.