We studied the clinicopathologic features of 42 cases of nasal-type extranodal natural killer (NK)/T-cell lymphoma in Singapore and compared our findings with other series reported in the Asian and Western populations. A panel of immunohistochemical stains, which included CD2, CD3, CD4, CD8, CD56, T-cell intracellular Antigen-1 and granzyme B, and in situ hybridization for Epstein-Barr virus encoded RNA (EBER) were performed. Polymerase chain reaction for T-cell receptor-gamma gene rearrangement using both gel and capillary electrophoresis were evaluated to determine the proportion of tumors which are of true T-cell lineage. We also studied the functional status of the overexpressed p53 protein in these lymphomas by correlating p53 expression with its downstream target protein, p21. In all, 31 out of 42 cases presented in the upper aerodigestive tract. The other sites of involvement included gastrointestinal tract, skin, soft tissue, testis, liver, spleen, bone marrow and brain. The tumors displayed characteristic morphologic features. In situ hybridization for EBER was detected in 41 out of 42 cases (97.6%). The only significant adverse prognostic factor identified was an International Prognostic Index of two or more. A significantly higher proportion of the tumors (27%), compared to previous studies, demonstrated monoclonal T-cell receptor-gamma gene rearrangement. There was, however, no difference in survival or clinicopathologic features between the true NK-cell tumors and their T-cell counterparts. Overexpression of p53 was present in 40% of the cases, but no significant difference in survival rate was detected in patients with p53 overexpression and there was no association between p53 overexpression with large cell morphology, and advanced stage of disease. These findings suggest that molecular aberrations other than those of the p53 pathway may be operative in the pathogenesis of this malignancy.

We studied 50 papillary lesions (25 papillomas and 25 papillary ductal carcinomas in situ, DCIS) diagnosed at Singapore General Hospital, for immunohistochemical expression of cytokeratin (CK) 5/6, CK14, and 34betaE12. The immunoscore (proportion of stained cells multiplied by staining intensity) was compared between the two groups. Cytokeratin expression was corroborated by confocal microscopy. Results were applied to a separate series of 43 papillary tumors from Hong Kong (HK). CK5/CK6, CK14, and 34betaE12 showed higher immunoscores in papillomas (mean values, 107.6, 186.6, and 113.1, respectively) than papillary DCIS (mean values, 12, 29.6, and 34.5, respectively; P<0.0001, P<0.001, and P<0.02, respectively). A cutoff immunoscore threshold of 50 appeared discriminatory between papilloma and papillary DCIS, and this value was applied to the HK cases, with CK5/CK6, CK14, and 34betaE12 correctly predicting 25 (89.3%), 26 (92.9%), and 27 (96.4%), respectively, of 28 HK lesions labeled as papillomas; while they corroborated 13 (86.7%), 13 (86.7%), and 5 (33.3%), respectively, of 15 HK cases diagnosed as papillary DCIS. Review of discordant cases showed that lesions were small, derived from core biopsies, or disclosed accompanying invasive carcinoma. When both SGH and HK cases were combined as a group, the sensitivity of an immunoscore of 50 or less in the diagnosis of papillary DCIS was 95%, 85%, and 62.5% for CK5/CK6, CK14, and 34betaE12, respectively, while the specificity was 86.8%, 94.3%, and 86.8%, respectively. CK immunohistochemistry can aid in evaluating papillary breast lesions. 34betaE12 does not appear as useful in identifying papillary DCIS.