Delayed Diagnosis of Basal Cell Carcinoma of the Upper Lip: The Possible Role of Incidental Multinucleated Foreign Body Giant Cells.

Herpes simplex and basal cell carcinoma (BCC) can have similar clinical presentations due to overlapping lesional morphology. We describe the unusual case of a BCC masquerading as herpes labialis due to a possible false-positive Tzanck smear. The confounding diagnosis led to a failed trial of valacyclovir and subsequent loss of the patient for 1 year before the lesion was biopsied and diagnosed as a BCC.