In Tzanck smear, multinucleated giant cells are seen in: (AIPG 2011)
A Tzanck smear is a cytologic technique commonly used in the diagnosis of herpes virus infections (simplex or varicella-zoster). An early vesicle, not a pustule or crusted lesion, is unroofed, and the base of the lesion is scraped gently with a scalpel blade. The material is then placed on a glass slide, air-dried, and stained with Giemsa or Wright's stain. Multinucleated giant cells suggest the presence of herpes.