Cytohistological correlation in pituitary tumor and immunological assessment with the help of Ki-67

Tumors of the pituitary gland and sellar region represent approximately 10-15% of all brain tumors. Pituitary adenoma (PA), the most common pathology of the pituitary gland, can be effectively subclassified only with the help of immunohistochemistry (IHC). This is important and needed for individual patient management.

The objective of the study was to analyze the importance of intraoperative imprint smear cytology and correlating with final histopathological diagnosis. Furthermore, to classify the different types of PA with the help of IHC, prolactin (PRL), adrenocorticotropic hormone (ACTH), and growth hormone (GH) and to predict the benign, atypical, or malignant nature of the tumor with the help of prognostic marker Ki-67.

A prospective study was done in 34 cases. The patients whose pituitary gland samples are referred from the endocrine and the neurosurgery department to the pathology department for histopathological examinations were selected. We have studied the clinical features, radiology and touch imprint cytology, histopathology, and IHC with the help of PRL, ACTH, GH, and Ki-67 of PA over 2 years.

In our study, we had 32 cases of PA of 34 cases over a span of 2 years. We have seen that there is a correlation between cytological and histological diagnosis of the subtypes of PA in 62% cases, and the Kappa statistics show a moderate extent of agreement (Kappa - 0.320, 95% confidence interval = 0.031-0.609). Ki-67 when compared to the radiological grading showed a high degree of comparability (Chi-square test: P < 0.001). All cases with invasion had a higher Ki-67. On using the Fisher's exact test, we found that the Ki-67 expression with GH-producing adenomas and ACTH-producing adenomas was comparable (P = 1.000) while in PRL-producing adenomas too this was not significant (P = 0.269).

PA can be effectively classified with the help of IHC. Intraoperative cytology is important in diagnosing PA, but histopathology remains the gold standard in diagnosing and differentiating PA from other pathologies of the pituitary gland. The radiological grading together with immunological classification and the prognostic markers of Ki-67 is important in deciding the benign or atypical nature of the adenomas thus helping in better patient management.