Value of Ki67 immunostain in identification of malignancy in serous effusions

Abstract

The distinction between malignant and benign serous effusions continues to be a challenging and a frequent problem to cytopathologists. Recently, immunostains employing various antibodies have improved the diagnostic accuracy of malignant effusions. We investigated the usefulness of Ki67 (MIB1) antigen immunostaining in the evaluation and diagnosis of malignant serous effusions. Cell block sections from a total of 54 cases of serous effusions cytologically diagnosed as malignant (28), suspicious (6), and benign (20) were immunostained with MIB1 monoclonal antibody to the Ki67 nuclear proliferation antigen according to the avidin‐biotin immunoperoxidase method. The patients were 30 women and 24 men with an average age of 58 yr. Ki67 (MIB1) immunostain labeling index (LI) values were higher than 20% in 23 of 28 (82%) cytologically malignant, in 3 of 6 (50%) suspicious, and in 1 of 20 (5%) benign/reactive. Further investigation revealed histologic, radiologic, and/or clinical evidence of malignancy in the 3 suspicious (but not in the benign/reactive) cases with Ki67 LI values higher than 20%. Correlation between Ki67 LI (>20%) and cytologic effusion type (benign, suspicious, or malignant) was statistically significant (P < 0.0001). Ki67 immunostaining has value as an adjunct testing to cytomorphology and other immunostains in distinguishing benign from malignant effusions. The addition of Ki67 immunostaining to conventional cytology appears more sensitive than cytomorphology alone and may assist in arriving at accurate diagnoses in suspicious cases with inconclusive cytomorphologic features. Diagn. Cytopathol. 1999;20:24–28. © 1999 Wiley‐Liss, Inc.

Immunocytochemistry: an indispensable technique in routine cytology

“…For Ki‐67 , a proliferative index over 20% indicates a malignant cell population. Unfortunately, some benign proliferations may also exceed this figure 43 …”

“…Unfortunately, some benign proliferations may also exceed this figure. 43 Adenocarcinoma, site specificity A cytological diagnosis of adenocarcinoma in a specimen procured from a given site will in most cases, with confirmatory clinical information, lead to a conclusive diagnosis such as primary carcinoma of the breast, lung, thyroid or pancreas. In this situation there is seldom a need to confirm the diagnosis with ICC.…”

Serous effusions: diagnosis of malignancy beyond cytomorphology. An analytic review

“…[51][52][53] Saleh et al have shown a statistically significant correlation between the Ki67 index and cytomorphology of benign (9%), suspicious (19%), and malignant (28%) cells. 50 However, cytomorphology should always remain the basis to differentiate benign from malignant serous effusions and Ki67 stain is a valuable adjunct in difficult cases, acting as a complementary tool to routine cytology.…”

Diagnostic value of p53 and ki67 immunostaining for distinguishing benign from malignant serous effusions

“…The expression of proliferative cell markers including ki67 in benign cases was explained by the possible autocrine or paracrine growth factors that upregulated the ki67 gene expression and hence increased the proliferative indices [33]. This explanation was proved by the demonstration of ki67 overexpression in normal breast and pancreatic exocrine cells in other studies [34,35].…”

“…On the other hand, Saleh et al [33] attributed the cause of low labeling index in some malignant cases to the down-regulation of ki67 gene by the effect of some autocrine and paracrine uncertain factors. Sikora et al [36] also attributed the cause of the false negative cases to the low proliferative and turnover activity in certain tumors or to technical factors that cause reduction or masking of ki67 expression.…”