Diagnostic Utility of Squash Cytology and its Correlation with Histopathology in Neuropathological Specimens.

INTRODUCTION : Brain is the most vital organ in our body. Unlike other systems of the body, lesions in central nervous system (CNS) cannot be localised with specific symptoms or signs. It needs an integrated approach. It involves the neurophysician, neurosurgeon, radiologist and pathologist. It is the pathologist who gives the final report and the treatment is based on the pathologist’s report. Hence, it is of paramount importance to diagnose CNS lesions with accuracy. BACKGROUND OF THE STUDY : Squash preparation is an effective, simple, rapid, relatively safe, and reliable technique for the diagnosis of central nervous system tumors. The knowledge of the squash preparation technique could be beneficial in centers where a facility for frozen sections is unavailable, in case of a power break-down, or a lack of trained technical personnel. Squash cytology is very useful in CNS lesions due to the intrinsic soft consistency of the brain tissue. In the era of stereotactic biopsies, where the amount of tissue fragment is very small, good preservation of fine cellular details can be obtained with squash cytology. Squash cytology is not affected by edema, hemorrhage, necrosis or calcification. The current study was undertaken to assess the diagnostic utility of squash cytology and to correlate with histopathological diagnosis. AIM OF THE STUDY : The aim of the study is to assess the diagnostic utility of squash cytology and to correlate with histopathology in neuropathological specimens. MATERIALS AND METHODS : This is a prospective study. The study was conducted in the Department of Pathology, Coimbatore Medical College, Coimbatore. The study was conducted after obtaining the ethical approval from the Ethical Review Committee of Coimbatore Medical College, Coimbatore. Fifty cases of Neuropathological specimens received between from March 2010 to June 2011 were assessed. The study subjects were patients admitted to the Department of Neurosurgery for space occupying lesions of brain and spinal cord. During surgery, upon opening the lesion, small bits of tissue measuring 1-2mm2 were taken in a fresh state and sent for squash cytology in gauze moistened with saline. The remaining tissues were fixed in 10% formalin and sent later for histopathology. In difficult cases where conclusion could not be made even with histopathology, special stains and immunohistochemistry were used as adjuvants to histopathology. Whenever there was difficulty in grading astrocytomas, tumor grading was done with Ki67/MIB-1 labelling index using immunohistochemistry. SUMMARY : The prevalence of CNS lesions reported at Department of Pathology, Coimbatore Medical College was 1.1%. The sensitivity of squash cytology in detecting CNS tumors was 97.62%. The specificity of squash cytology in detecting CNS tumors was 75%. The positive predictive value of squash cytology was 95.35%. The negative predictive value of squash cytology was 85.71%. The percentage of false positive results was 25%. The percentage of false negative results was 2.38%. CONCLUSION : Squash cytology is a sensitive and specific modality for diagnosing space occupying lesions of brain and spinal cord. The method is easy, rapid and inexpensive. Details of cellular morphology are well seen in squash cytology. Hence squash cytology can be used as a reliable diagnostic tool in developing countries like India, since the cost of cryostat is prohibitive and unlike cryostat, squash cytology does not require any electricity for slide preparation. Moreover, cryostat needs an experienced microtomist to cut the sections and the problems of freezing artefacts cause diagnostic pitfalls. Despite the advantages, Squash cytology should be used as a preliminary investigation and should always be confirmed with Histopathology which is the golden standard. It should never be used solely for diagnostic or therapeutic purposes