A Study On The Proliferative Activity Of Nasal NK/T Cell Lymphoma

【Background】Nasal NK/T-cell lymphoma is a peculiar non-Hodgkin lymphoma. Thetumor is located in extranodal parts, especially in the nasal cavity. In2001WHOclassification of tumors of haematopoietic and lymphoid tissues, nasal NK/T celllymphoma is described as a new entity due to its tumor cell biology combinedwith clinical features, anatomical site, immunophenotype, genotype andEpstein-Barr virus (EBV) status. The incidence of the tumor variesgeographically, with a higher incidence in Mexico, Asia, Central and SouthAmerica rather than that in Europe and North America.Most of the nasal NK/T cell lymphoma cases appear to express NK-cellneoplasms (EBV+, CD56+), but there are few cases with an EBV+CD56-cytotoxic T-cell phenotype. Immunological studies show that T cell and NK cell are closely related during differentiation because they have identical precursorcells. Modulated by different biological mechanisms, the precursor NK/T cellcan be differentiated into mature T or NK cell.Nasal NK/T cell lymphoma is characterized by its aggression, representingnasal cavity and midfacial destroy in clinic. Histologically, the tumor cells aredemonstrated as mass of coagulative necrosis, a heavy admixture ofinflammatory cells and polymorphic tumor cells with an angiocentric andangiodestructive growth pattern. Therefore, nasal NK/T cell lymphoma isconsidered with a high malignancy. However, we found that the progression ofthe patients with this tumor had different progression course in clinic. Some ofthe patients did progress rapidly, while some patients progressed slowly. It ishypothesized that this difference of malignancy might be due to the differentproliferative activity of tumor cells. Hence, in this study we usedimmunohistochemistry of Ki-67and PCNA to assess the proliferative activity oftumor cells. The results indicated that the proliferative activity of the tumor cellswas quite different, which was meaningful for further diagnosis of nasal NK/Tcell lymphoma.【Objective】To detect the proliferative activity of tumor cells by immunohistochemistryand provide a potential new factor for nasal NK/T cell lymphoma.【Methods】1. Retrieving the samples and reconfirming the diagnosis.2. Detecting the proliferative activity by immunohistochemical staining ofKi-67and PCNA in31nasal NK/T cell lymphomas and12nasopharyngealreactive lesions and figuring out the labeling index of Ki-67and PCNA. 3. Comparing the difference of proliferative activity between the tumors andreactive lesions by statistical analysis.【Results】1. The diagnosis of nasal NK/T cell lymphoma in all31cases was furtherconfirmed by morphological and immunophenotypic analysis.2. Ki-67LI in31cases of the tumor was0.37±0.03and in the control groupwas0.07±0.02．Statistically, there was a significant difference between thetwo groups (P <0.001). Dividing the31cases of the tumor into two groups，i.e．high and low proliferative ones based on the mean value of Ki-67LI,17cases (54.8%) showed higher Ki-67LI and14cases (45.2%) showedlower Ki-67LI. Importantly，Ki-67LI in the low proliferative group wasstill significantly higher than that of reactive lesions (P <0.001)．3. PCNA LI in31cases of the tumor was0.42±0.02and in the control groupwas0.17±0.01．Statistically, there was a significant difference between the2groups (P <0.001). Dividing the31cases of the tumor into2groups，i.e．high and low proliferative ones based on the mean value of PCNA LI,15cases (48.4%) showed higher PCNA LI and16cases (51.6%) showedlower PCNA LI. Importantly，PCNA LI in the low proliferative group wasstill significantly higher than that of the control group (P <0.001)．4. There existed a positive correlation between Ki-67LI and PCNA LI, and thecoefficient was0.88, indicating that the two antibody had a good correlationin labeling the proliferative activity of tumor cells.5. In nasal NK/T cell lymphoma, higher Ki-67LI or PCNA LI was oftenpositively correlated with large area of necrosis (P <0.001). 【Conclusions】Nasal NK/T cell lymphoma is a kind of malignant tumor with obviouslyheterogeneous proliferative activity．Ki-67LI and PCNA LI are useful in apathological diagnosis of nasal NK/T cell lymphoma.