Role of Scrape Cytology as an Adjunct to Fine Needle Aspiration Cytology in Diagnosis of Thyroid Lesions.

Abstract

Scrape cytology is an important diagnostic tool. It has been used in many tissue types as an adjunct or replacement for frozen section/ intra operative consultation. This study was done to evaluate the role of scrape cytology in the diagnosis of thyroid lesions, its role as an adjunct to Fine Needle Aspiration Cytology (FNAC) and application of this technique for intra-operative consultation. A prospective study on 50 thyroid neoplasms received over a period of 18 months (Nov 2014- March 2016) was conducted. Scrapings obtained from the fresh cut surface of thyroid specimens before formalin fixation, were smeared uniformly on to glass slides, and immediately fixed in 95% ethyl alcohol for rapid Haematoxylin and Eosin (H&E). Cytological findings were compared with pre-operative FNAC findings and histopathological diagnosis. Variables taken in to consideration while assessing the smears included cellularity, nuclear, cytological details and amount of colloid. There were total of 50 patients. Out of the 50 patients, 15 were diagnosed as benign on scrape; of which 100% of cases were true negative for malignancy and five malignant cases were diagnosed as benign-false negative rate of 16.1%; four (8%) were deferred (non-diagnostic) with a true positive rate of 83.3%. Histopathological correlation was available in all cases. The overall diagnostic accuracy of scrape cytology was 89.1% with sensitivity and specificity of 83.87% (C.I.; 66.27% to 94.55%) and 100% (C.I; 76.84% to 100.00%) respectively. Fine Needle Aspiration results were available in 41 cases of which 2 were non-diagnostic. Of the remaining 39 cases 19 were benign and 20 were malignant with false negative rate of 40% and true positive rate of 60%. The overall diagnostic accuracy of FNAC was 64.1% with sensitivity and specificity of 60% (C.I.; 40.6% to77.3 %) and 77.78% (C.I; 39.9% to 97.1%) respectively. We conclude that scrape cytology can act as a useful adjunct to FNAC and is a good procedure for intra-operative consultation. It is especially helpful in neoplasms diagnosed as suspicious for papillary carcinoma on aspiration and may obviate the need for a second procedure for completion thyroidectomy.