Original Paper Oesophageal basaloid squamous cell carcinoma: a unique clinicopathological entity with telomerase activity as a prognostic indicator King Y. Lam 1 *, Simon Law 2 , John M. Luk 2 and John Wong 2 1 Department of Pathology, University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong 2 Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong * Correspondence to: Dr K. Y. Lam, Room 313, Clinical Pathology Building, Department of Pathology, University of Hong Kong Medical Centre, Queen Mary Hospital, Pokfulam Road 102, Hong Kong E-mail: akylam@hotmail.com Received: 10 January 2001 Revised: 30 March 2001 Accepted: 5 July 2001 Published online: 28 September 2001 Abstract Oesophageal basaloid squamous cell carcinoma (BSCC) is uncommon and has been reported to have a worse prognosis than squamous cell carcinomas (SCCs), but this tumour has not been fully characterized. The aim of the present study was to analyse the clinicopathological features of a large cohort of patients with oesophageal BSCC treated at a single institution. The pathology of 756 primary oesophageal cancers treated between January 1989 and December 1998 was reviewed. Tumours that fulfilled the diagnostic criteria of BSCC were identified and were compared with SCC. Their expression of MIB-1, DNA ploidy, and telomerase activity were also studied. Thirty Chinese patients (25 men and five women) with BSCC were found, comprising 4% of patients with oesophageal cancer treated by surgical resection in the study period. Their median age was 67 years (range 40–78 years). Dysphagia was usually the main presenting symptom. Other concomitant malignant tumours were seen in three patients and paraneoplastic glomerulopathy in one. Five tumours were located in the upper third, 19 in the middle third, and six in the lower third. The median length was 5.8 cm (range 2–12 cm). The median MIB-1 score of BSCC was 750 (range 400–858) and was higher than that of SCC ( p=0.003). The primary tumour and metastatic BSCC were aneuploid, as detected by flow cytometric analysis in nine patients. Telomerase activity was positive in 95% (19 out of 20) of the cases analysed. The 5-year survival of patients with BSCC was 12%. Distant metastases were seen in 53% (n=16); lung and liver were the most common sites. The median survival of patients with tumours which had a high level of telomerase activity was significantly shorter than those with low levels of telomerase activity (1 vs. 27 months) ( p=0.001). The median survival of patients with BSCC and SCC was 26 and 16 months, respectively ( p=0.3). In conclusion, BSCC has distinctive clinicopathological features and its long-term prognosis is no worse than SCC. The level of telomerase activity may have a prognostic role. Copyright # 2001 John Wiley & Sons, Ltd. Keywords: oesophagus; basaloid squamous carcinoma; squamous cell carcinoma; telomerase Introduction In Asian populations, squamous cell carcinomas (SCCs) account for more than 90% of malignant oesophageal tumours, many of which are moderately differentiated [1]. In recent years, an uncommon variant of SCC, termed basaloid squamous cell carci- noma (BSCC), has been identified [2–11]. BSCC has a predilection for the upper aerodigestive tract. The World Health Organization (WHO) classification included BSCC under the category of epithelial tumours in the larynx, hypopharynx, and trachea in the Histological Typing of Tumours of the Upper Respiratory Tract and Ear [12]. However, BSCC is not included in the category of epithelial tumours of the oesophagus in the Histological Typing of Tumours oftheOesophagusandStomach [13]. Studies have shown that proliferative markers and tumour-related genes may affect the prognosis of patients with oesophageal cancer [14]. Telomerase is an important ribonucleoprotein that acts as an enzyme for the maintenance of telomeres during cell division [15]. The enzyme is inactive in adult somatic cells, except for germ cells, activated lymphocytes, and stem cells of regenerative tissues. Telomerase activity has been demonstrated in oesophageal SCC and cell lines in recent years [16–18], but the role of telomerase activity in oesophageal BSCC has not been demonstrated. In the present study, we reviewed the pathological features of resected oesophageal cancers over a 10-year period; tumours with features of BSCC were identified. The clinicopathological features of BSCC were compared with those of SCC. Proliferative activity, DNA ploidy, and telomerase activity in BSCC were also assessed. Materials and methods Data collection The tissue samples were collected from patients with oesophageal cancers treated at the Department of Surgery, University of Hong Kong Medical Centre, Journal of Pathology J Pathol 2001; 195: 435–442. DOI: 10.1002/path.984 Copyright # 2001 John Wiley & Sons, Ltd.