Oral lesions of pemphigus are a common manifestation of the disease, and often precede the severe skin involvement. The histopathology of the oral lesion is invariably diagnostic for pemphigus. The oral cytologic smear is highly suggestive of the disease. Where a diagnosis with grave implications is to be made, as for pemphigus, all available diagnostic criteria should be utilized. These should include both the oral biopsy and the oral cytologic smear.
Shklar G, Cataldo E. Histopathology and Cytology of Oral Lesions of Pemphigus. Arch Dermatol. 1970;101(6):635-641. doi:10.1001/archderm.1970.04000060007002