The diagnostic value of the Tzanck smear test for basal cell carcinoma and its subtypes

Definitive diagnosis of basal cell carcinoma is made through histopathologic examination. However, there is a need for alternative, non-invasive diagnostic methods in the following situations: when tumors are found in an area that is important cosmetically, when planning a treatment other than surgical excision, where a new lesion is suspected of recurring over an excision scar, in selecting proper surgical limits before surgery, especially in determining aggressive type basal cell carcinomas, in distinguishing basal cell carcinoma from other malignant skin tumors, and in situations where patients have many suspected tumors. This study aims to evaluate the value of cytology in diagnosing basal cell carcinoma, its subtypes and investigating how duration of experience in cytological diagnosis contributes to correct diagnosis. Sixty-one patients clinically suspected of having basal cell carcinoma were included in this study, and Tzanck smears were taken from a total of 83 lesions. The specimens of basal cell carcinoma and its subtypes were evaluated for diagnosis by two dermatologists, one with little experience (Dermatologist A) and the other had more experience (Dermatologist B) in cytology. Histopathological diagnosis was considered to be the definitive diagnosis. Histopathological diagnoses were compared with the cytological diagnoses of the two dermatologists for 72 tumors definitively diagnosed as basal cell carcinoma with subtypes determined, and agreement between the cytological diagnoses of the dermatologists was evaluated. Both dermatologists correctly diagnosed all basal cell carcinomas and there was a very high degree of agreement between them (κ=1, pK=0.001). The two dermatologists were not able to correctly diagnose four tumors of infiltrating, aggressive subtypes. Between cytological and histopathological diagnoses; in mixed (Dermatologist A: κ=0.289, p=0.014; Dermatologist B: κ=0.296, p=0.007) and pigmented (Dermatologist A: κ=0.354, p=0.001; Dermatologist B: κ=0.215, p=0.001) types of tumors, both dermatologists were at a low level of agreement, in keratotic type tumors, Dermatologist A (κ=0.550, p=0.001) and Dermatologist B (κ=0.164, p=0.087) were at medium and weak levels of agreement respectively, and in cystic type (Dermatologist A: κ=0.045, p=0.399; Dermatologist B: κ=0.040, p=0.225) tumors, both dermatologists were at a weak level of agreement. For nodular type (Dermatologist A: κ=-0.052, p=0.443; Dermatologist B: κ=-0.075, p=0.344) tumors, no agreement was demonstrated between cytological and histopathological diagnosis. Cytology is a precise and reliable method for the diagnosis of basal cell carcinoma and short-term training in cytology may allow for accurate diagnosis of this tumor. While the variation of subtypes of basal cell carcinoma, and especially the number of aggressive subtypes was low, cytology may be considered not to be a precise and reliable diagnostic method for determining histopathological subtypes of this tumor.