Archives of Pathology and Laboratory Medicine. 2008 Apr;132(4):694-7. [Link]

Taheri ZM, Mehrafza M, Mohammadi F, Khoddami M, Bahadori M, Masjedi MR.

National Research Institute of Tuberculosis and Lung Disease, Department of Pathology, Shahid Beheshti University of Medical Sciences, Tehran, Iran.


Context: The differentiation of benign mesothelial proliferations from malignant mesotheliomas may be difficult, especially when evaluating small specimens from pleural biopsies.

Objective: To explore the potential value of 2 proliferative cell markers, Ki-67 and restrictedly expressed proliferation–associated protein 86 kDa (repp86), in distinguishing between malignant mesothelioma (MM) and benign reactive mesothelial hyperplasia (MH).

Design: Thirty-six cases of MM from 26 men and 10 women with a mean age of 62.9 years (range, 36–80 years) and 22 cases of benign reactive MH from 14 male and 8 female patients with a mean age of 51.5 years (range, 15– 88 years) were included in this study. The proliferative status of the lesions was assessed by immunohistochemistry using monoclonal antibodies to Ki-S2 (repp86) and Ki-S5 (Ki-67). The labeling indices were quantified.

Results: The mean labeling indexes for Ki-67 in MM and benign reactive MH were 24.6% (range, 1%–66%) and 6.23% (range, 0%–25%), respectively. The mean labeling indexes for repp86 in MM and benign reactive MH were 26.3% (range, 0%–50%) and 3.26% (range, 0%– 21%), respectively. The average proliferative cell count was significantly higher in MM compared with benign reactive MH (P < .001). Furthermore, both markers showed a significant correlation in their expression in MM and benign reactive MH (r = 77.5, P < .001). Sensitivities of 88% and 92% and specificities of 92% and 94% were obtained at a cutoff point of 9% for Ki-67 and repp86, respectively.

Conclusions: Used in combination, Ki-67 and repp86 appear to be useful markers in differentiating MM from benign reactive MH.