Original article Prognostic value of subclassification of T2 tumours in patients with gastric cancer D. Nitti 1 , A. Marchet 1 , S. Mocellin 1 , G. M. Rossi 1 , A. Ambrosi 2 and R. Mencarelli 3 1 Clinica Chirurgica II, Department of Oncological and Surgical Sciences, University of Padua, and 2 Istituto Oncologico Veneto, Istituto Ricovero e Cura a Carattere Scientifico (IRCSS), Padua, and 3 Department of Pathology, General Hospital Rovigo, Rovigo, Italy Correspondence to: Professor D. Nitti, Clinica Chirurgica II, Dipartimento di Scienze Oncologiche e Chirurgiche, Universit` a di Padova, Via Giustiniani 2, 35128 Padova, Italy (e-mail: donato.nitti@unipd.it) Background: This study was designed to evaluate the prognostic value of tumour stage T2 subcategorization (T2a and T2b) in patients with gastric carcinoma. Methods: Clinicopathological details of a prospective series of patients who had radical resection of gastric adenocarcinoma in a single institution were analysed. Univariable and multivariable survival analyses were performed with the log rank test and Cox’s model respectively. Results: Of 373 evaluable patients, 49 (13·1 per cent) had a T2a and 143 (38·3 per cent) a T2b tumour. At a median follow-up of 35·5 months, the 5-year overall survival rate was 73 and 31·1 per cent for patients with T2a and T2b lesions respectively (P < 0·001). On multivariable analysis, T stage remained an independent prognostic factor. Compared with T1a, the mortality risk for patients with T1b (hazard ratio (HR) 1·00; P = 0·992) and T2a (HR 0·97; P = 0·916) tumours was similar; by contrast, the risk of death associated with T2b (HR 1·81; P = 0·031) and T3 (HR 1·89; P = 0·038) lesions was significantly greater than for T1a tumours. Conclusion: Subclassification of T2 tumours should be undertaken routinely in order to stratify patients with gastric cancer more accurately in terms of their mortality risk. Paper accepted 23 February 2009 Published online in Wiley InterScience (www.bjs.co.uk). DOI: 10.1002/bjs.6487 Introduction The number of metastatic lymph nodes (N stage) and the depth of the primary tumour (T stage) are considered the most reliable prognostic indicators for patients with radically resected gastric carcinoma 1–4 . Although assessment of N stage may be influenced by the extent of lymph node dissection, classically termed D1 and D2 5,6 ,T stage can be assessed readily by pathological examination of the primary tumour as limited to the mucosa or submucosa (T1), involving the muscularis propria or subserosa (T2), invading the serosal layer (T3) or infiltrating adjacent structures (T4) 6,7 . Although T1 and T3 are the most common categories in patients who have radical surgery, T2 is found in 10–38 per cent of patients 1,8–12 . In a recent Italian study of 1853 radically resected patients with gastric cancer 13,14 , T2 tumours were found in 543 patients (29·3 per cent), a proportion similar to that for T1 tumours (585 patients, 31·6 per cent). The College of American Pathologists has suggested that subclassification of T2 into T2a (tumour confined to muscle) and T2b (tumour extends to subserosa) is justified because postsurgical survival after resection for cure is significantly different for patients with T2a and T2b lesions 15 . In line with this recommendation, the most recent International Union Against Cancer–American Joint Committee on Cancer (UICC–AJCC) staging system subclassifies T2 into T2a and T2b 16 , although these subcategories are not maintained when stage grouping is performed 16 , limiting the prognostic power of the tumour node metastasis (TNM) classification. The prognostic value of T2 subclassification is supported by several lines of evidence. Nodal involvement is significantly less for T2a than for T2b tumours 8–10,17,18 ; the prevalence of pathological (p)N1 is similar in the two subgroups, but that of pN2 and pN3 is higher for T2b than for T2a lesions 8 . Consequently recurrence rates and mortality are significantly lower for T2a than T2b tumours 8,9 . Copyright  2009 British Journal of Surgery Society Ltd British Journal of Surgery 2009; 96: 398–404 Published by John Wiley & Sons Ltd