6. Ross GL, Soutar DS, MacDonald DG et al. Sentinel node biopsy in head and neck cancer: preliminary results of a multicenter trial. Ann. Surg. Oncol. 2004; 11; 690–696. 7. Hakam A, Nasir A, Raghuwanshi R et al. Value of multilevel sectioning for improved detection of micrometastases in sentinel lymph nodes in invasive squamous cell carcinoma of the vulva. Anticancer Res. 2004; 24; 1281–1286. 8. Moore RG, Granai CO, Gajewski W et al. Pathologic evaluation of inguinal sentinel lymph nodes in vulvar cancer patients: a comparison of immunohistochemical staining versus ultrastaging with hematoxylin and eosin staining. Gynecol. Oncol. 2003; 91; 378–382. 9. Tschopp L, Nuyens M, Stauffer E et al. The value of frozen section analysis of the sentinel lymph node in clinically N0 squamous cell carcinoma of the oral cavity and oropharynx. Otolaryngol. Head Neck Surg. 2005; 132; 99–102. Loss of p16 INK4 expression in invasive squamous cell carcinoma of the uterine cervix is an adverse prognostic marker DOI: 10.1111/j.1365-2559.2006.02510.x Sir: The cyclin-dependent kinase inhibitor p16 is known to be overexpressed in cervical intraepithelial neoplasia and many invasive cervical carcinomas. 1–3 In normal cells p16 acts as an inhibitor of cellular proliferation and is often inactivated in non-cervical tumours. 4 We evaluated whether p16 expression is of prognostic significance in invasive cervical carcinoma. The study population comprised 130 patients with invasive squamous cell carcinoma of the uterine cervix whose radical hysterectomy specimens were seen at the Institute of Pathology, University Hospital of Leipzig, between 1992 and 1996. Tumour slides were re- examined and a representative area marked on the slide. Two tissue microarrays (TMA) were constructed to sample two cores per tissue block. Slides from the TMA were cut at 4 lm and stained for p16 (clone 16PO4; Neomarkers Laboratories, Fremont, CA, USA; 1 : 1000 dilution, heat antigen retrieval). Any degree of immunoreactivity was considered to be p16+ (Figure 1). As expected, lymph node status (P< 0.0001), depth of stromal invasion (P ¼ 0.0354) and tumour stage (P ¼ 0.0355) were significant predictors of recurrence-free survival (Figure 2). Of the 115 cases for which there were p16 staining data, 96 were positive for p16 expression (83.5%). On univariate analysis, loss of p16 expression showed statistical significance (P ¼ 0.0198) as a predictor of decreased disease-free survival (Figure 3). The statistical signi- ficance of p16 expression was retained for node- negative (P ¼ 0.0044) but not node-positive patients, when the results were stratified for nodal status (Figure 3). On multivariate analysis p16 approached significance (P ¼ 0.060) as a prognostic indicator, independent of nodal status and depth of invasion and tumour stage (Table 1). While genetic alterations in the p16 gene are uncommon in cervical cancer, 1,5–7 squamous cell carcinoma (SCC), high-grade cervical intraepithelial neoplasia (CIN) and adenocarcinoma of the cervix H.M. and D.J.v.N. contributed equally to this work (joint first authors). a b Figure 1. Immunoreactivity for p16. a, p16+ tumour. b, p16– tumour. 542 Correspondence Ó 2006 The Authors. Journal compilation Ó 2006 Blackwell Publishing Ltd, Histopathology, 49, 538–558.