Oral carcinoma cuniculatum: two cases illustrative of a diagnostic challenge.

Carcinoma cuniculatum is a rare variant of squamous cell carcinoma originally described on the sole of the foot and for a long time believed to be restricted to the skin. However, since its first description in 1954, several cases have been reported at other sites. Carcinoma cuniculatum characteristically invades the underlying subcutaneous, submucosal, or bone tissues, forming so-called "rabbit burrows," with crypts filled with keratin that are of utmost importance for distinguishing this neoplasm from other variants of squamous cell carcinoma. Oral carcinoma cuniculatum is an even rarer entity that is frequently misdiagnosed initially, a phenomenon described in about one-third of previously reported cases. The aim of this report is: (1) to describe the clinicopathologic features of 2 new cases of oral carcinoma cuniculatum, initially misdiagnosed as infected orthokeratinized cyst and abscess, respectively; and (2) to review the related English language literature.