What is the discrepancy rate between frozen section (FS) and permanent section analysis of operative margins from high-risk cutaneous squamous cell carcinomas (SSC) of the head and neck?
Background: SSC is the second most common skin cancer, with approximately 700,000 new U.S. cases diagnosed each year. Several treatment options exist, but Mohs micrographic surgery remains the primary treatment modality. To achieve negative margins, the routine use of FS has also been well established, but for some tumors FS accuracy remains unclear.
Explore this issue:March 2015
Study design: Retrospective review of 41 patients undergoing excision of advanced head and neck SSCs at a single tertiary institution between 2010 and 2013.
Setting: Massachusetts Eye and Ear Infirmary.
Synopsis: Twenty-two of the 41 cases were referred for recurrent cutaneous SCC; among these, initial treatments included Mohs micrographic surgery, wide local excision, and an unknown excision modality. Mean tumor defect size was 5.1 cm. Lymphovascular and perineural invasion was identified in 11 and 19 cases, respectively. Discrepancy between FS and permanent margins was identified in 10 of 247 FS samples and in eight of the 41 cases. Tumors that were known to have undergone prior Mohs resection had a false-negative rate of 44.4% compared with a false-negative rate of 17.3% in recurrent tumors resected by a different technique. Tumor defect >4 cm had an 8.7% false-negative rate, while tumor defect <4 cm had a 35.3% false-negative rate. The false-negative rates for tumors demonstrating poorly differentiated subtype, lymphovascular invasion, and perineural invasion were 14%, 36%, 26%, respectively. The positive and negative predictive values of poorly differentiated carcinoma, lymphovascular invasion, and perineural invasion in predicting discrepancy between FS and permanent margins were 14% and 82%, 36% and 84%, and 26% and 92%, respectively.
Bottom line: There was a moderate discrepancy rate between FS and permanent section analysis of operative margins from high-risk cutaneous squamous cell carcinomas of the head and neck. The presence or absence of certain histopathologic features appears to be associated with a higher rate of FS discrepancy.