A comparison of touch imprint cytology and Mohs frozen-section histology in the evaluation of Mohs micrographic surgical margins.
BACKGROUND
Touch imprint cytology (TIC) is commonly used in the diagnosis of tumors and has been applied to margin analysis of breast lumpectomy specimens with good success.


OBJECTIVE
Our purpose was to determine the diagnostic adequacy of TIC for identifying positive and negative Mohs surgical margins for basal cell carcinoma (BCC) excisions, compared with the "gold" standard, Mohs tangential sectioning.


METHODS
Fifty-eight patients undergoing 69 Mohs micrographic surgical procedures for biopsy-proven BCC were included in this study between October 1998 and January 1999. Patients were excluded if the neoplasms were of another histologic type, including BCCs with squamous features. One hundred sixty-six touch imprint slides were prepared from 166 fragments of skin tissue excised during MMS. Touch imprint slides were evaluated blindly and independently by two pathologists, one of whom was also a cytopathologist. The slides were diagnosed as positive for tumor, negative for tumor, or, rarely, atypical but suspect for tumor. Discrepancies between the pathologists' interpretations were re-evaluated with the use of a two-headed microscope and a consensus was reached. After all cytologic interpretation was completed, the results were compared with the histologic diagnosis rendered for each fragment of tissue by the Mohs surgeon.


RESULTS
The prevalence of a positive margin by histologic confirmation was 55% overall, 60% for recurrent or sclerosing lesions, and 51% for nonsclerosing or recurrent lesions. The overall accuracy of this technique in identifying true positive and true negative margins was 71%. The sensitivity of TIC for identifying a positive margin was approximately 50% for all BCC types. The specificity was approximately 90% for all BCC types.


CONCLUSIONS
TIC is inadequate for identifying positive margins compared with the "gold" standard, MMS.
Departments of Dermatology and Pathology, University of Utah Health Sciences Center, Salt Lake City 84132, USA. scott@derm.med.utah.edu
S R
SR
Florell
L J
LJ
Layfield
J W
JW
Gerwels
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002280:Basal Cell Carcinoma / Q000473:pathology* / Q000601:surgery*; D003584:Cytological Techniques; D005629:Frozen Sections; D006801:Humans; D008875:Middle Aged; D015580:Mohs Surgery; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000473:pathology* / Q000601:surgery*