Tissue imprint for molecular mapping of deep surgical margins in patients with head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide, comprising approximately 5% of all newly diagnosed cancer cases in USA.1,2 The overall 5-year survival rates of HNSCC are approximately 60% but have not substantially changed despite progress in understanding the molecular underpinnings of disease and therapeutic innovation over the last two decades.1–3 HNSCC patients experience a high rate of local recurrence (10–40%) even when the surgical margins are tumor-free by histopathological examination.4 Local recurrence is clinically defined as occurring within 2 cm of the index tumor within three years of the end of treatment and is attributed to regrowth of residual fully transformed cancer cells that survived primary and adjuvant treatment.5 Second primary or field tumors are relapses not fulfilling these criteria and may be derived from a surrounding mucosal field containing partially genetically altered cells.6,7 The field may give rise to new invasive carcinomas when these cells undergo additional genetic alteration.8,9,10 p53 mutations, present in 50–60% of HNSCC, have been used as a molecular marker for assessment of surgical margins demonstrating value in predicting local and regional control.11–13 Other molecular markers including microsatellite alterations, eIF4E overexpression, and quantitative methylation have also been used to detect minimal residual disease in surgical margins and predict local recurrence of HNSCC.14–16 Most reports have taken samples from the mucosal surgical margin but not deep tissues of surgical defects. However, some investigators have provided evidence suggesting that deep margins are more predictive of local recurrence.17 Because surgical deep margins are commonly extensive and only tested intraoperatively by harvesting small representative tissue pieces for frozen section, residual tumor cells at the cut surface may be left undetected in surgical fields and only discovered on processing of the bulk resection specimen. This is done by sampling representative sections from key areas of the tumor specimen after formalin fixation and is reported days later after wound reconstruction and initial healing has occurred. Proper orientation of the specimen is dependent on communication between the surgeon and pathologist, and precise relocation of any close or positive final margins is hampered by the lack of landmarks within deep tissues such as the intrinsic tongue musculature to guide efforts at additional resection or targeted radiation. Tissue imprinting techniques have been described for assessment of residual tumor at the prostate capsule.18 The tissue imprints collected from the cut surface of specimens may permit tissue-specific molecular profiling that allows the detection of residual tumor cells from the entire deep margin, at a concentration below that detected by light microscopy. This technique has not been tested for HNSCC. This study examined the feasibility of tissue imprinting and molecular mapping for detection of residual tumor cells at deep surgical margins in patients with HNSCC.