| IntroductionSputum cytology is regarded by many clinicians as a non-invasive,cheap and simple test for the diagnosis of lung cancer.It complements radiology in the diagnostic workup of lung cancer patients and can be useful for identifying lung carcinoma, especially at the early and occult stages.However,it has shown a low yield in prospective screening trials and is of little or no value in the identification of peripheral cancers.The major limitation of the sputum smear method has been variable quality due to contamination with blood,saliva or inflammatory cells.The thin-layer cytology test(TCT) is a useful cytological technique and its clinical application was approved by the Food and Drug Administration(FDA).It is successfully used in cervical cytology for the preparation of clear cell monolayers through the removal of mucus,necrotic material and inflammatory cells.Sputum sediment section examination is also an important and simple method for identifying lung carcinoma.It collects more sputum specimens and retains some histological structures,so its positive rate of lung carcinoma is higher.In addition,immunocytochemical stain can be applied which is very important to type lung cancer.This study aimed to directly compare the TCT and sputum sediment section examination with the conventional pick-and-smear(CP) method,with respect to the quality of the slides and diagnostic sensitivity.The use of the TCT and sputum sediment section examination for the diagnosis of lung cancer was also evaluated. Materials and Methods1.MaterialsSputum specimens from 107 patients with lung cancer confirmed by surgical pathology or bronchoscopy biopsy were enrolled in this study.2.Methods(1) Conventional pick-and-smear method:four smears were prepared from fresh, unfixed sputum and immediately fixed in 95%ethanol and stained with Papanicolaou.(2) TCT:resuspend the sputum in 30ml CytoLyt solution and 7-8 drops digest liquid(1,4- dithiothreitol) directly for 10min.The sample was centrifuged at 2,500 rpm for 5min,and the supernatant was removed.The cell pellet was resuspended, placed in the PreservCyt solution for 10min,and then processed on the ThinPrep processor.ThinPrep-processed slides were fixed in 95%ethanol for 10min,and Papanicolaou staining was performed.(3) Sputum sediment section method:The residual sputum was transferred to a tube with 95%ethanol.The sample was centrifuged at 2,500 rpm for 5min and then cut down the sputum sediment.The sputum sediment was paraffin-embedded,sliced 4μm section.2 sections were HE stained.(4) Immunocytochemical stain:4μm sections were routinely deparaffinized in xylene and rehydrated in graded ethanols.Immunocytochemical staining was performed by the avidin-biotin immunoperoxidase technique using diaminobenzidine as the chromogen with monoclonal antibodies to CKH(Maixin,Clone 34βE12),CK7 (Maixin,Clone OV-TL 12/30+72.2),TTF-1(Maixin,Clone 8G7G3/1),NSE(Maixin, Clone E27).Results1,In comparison with the CP method,TCT demonstrated a number of advantages. First,screening time was reduced and screening efficiency was increased due to the decreased areas of cell monolayers.Second,the slides had a clearer background.Thus, abnormal and tumour cells were more readily discernible.Regardless of cell type,the cells were clearly stained and their morphology was well preserved.The microscopic fine structure of the nuclear envelope,nucleoli and chromatin was also clearly discernible and stereoscopic.2,In comparison with the CP method,sputum sediment section examination also demonstrated a few advantages.There was no artificial picking,so it always retained some histological structures and was easily observed.It collected more sputum specimens,so the background was not as clean as TCT.However,the cancer cells were clear and there was no cell overlapping.3,The positive rate of CP was only 57.0%(61/107) and the positive rate of TCT was 72.0%(77/107).This difference between the two methods was significant(P＜0.05). The positive rate of sputum sediment section examination was 70.1%(75/107).The difference between CP and sputum sediment section examination was significant (P＜0.05).When TCT and sputum sediment section examination were evaluated in combination,the positive rate was 83.2%(89/107),significantly higher than the CP method alone(57.0%,P＜0.01),TCT alone(72.0%,P＜0.05),sputum sediment section examination alone(70.1%,P＜0.05).4,In 17 cases which were not diagnosed clearly,9 cases were diagnosed as finding cancer cells or suspicious cancer cells and 5 cases were celluar atypical hyperplasia.The immunocytochemical stain results showed:2 cases were CKH positive and belonged to squamous cell carcinoma;4 cases were CK7 and TTF-1 positive and belonged to adenocarcinoma;1 was NSE positive and belonged to small cell lung cancer;3 cases were not applied immunocytochemical stain because of lack of cells or sections falling off.The residual 4 cases were proved as celluar hyperplasia.Conclusions1,TCT is a useful and easily performed technique that can be widely applied. 2,Combination of TCT and sputum sediment section exanimation appears to be of great value in clinical diagnosis of lung carcinoma.Espesically for the patients with central located mass suspected squamous cell carcinoma,it will increase the positive rate of squamouse cell carcinoma.3,When using immunocytochemical stain,the positive rate increased.
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