Clinical significance of peritoneal cytology including cell block method and immunohistochemical analysis in pretherapeutic diagnosis of histological subtype for excluding clear cell and mucinous adenocarcinoma from eligibility for neoadjuvant chemotherapy

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16566 Background: Several clinical trials of neoadjuvant chemotherapy for advanced ovarian cancer have been conducted. However, clear cell and mucinous adenocarcinoma should be excluded from the eligible criteria, because these two histological subtypes are resistant to chemotherapy, and the completeness of cytoreduction is the most prognostic factor in survival. In this study, we verified the significance of peritoneal cytology with cell block method and immunohistochemical (IHC) analysis in the pretherapeutic diagnosis of histological subtype in advanced ovarian cancer. Methods: Forty-one patients with advanced epithelial ovarian or primary peritoneal cancer, consisting of 8 serous (S), 9 endometrioid (E), 5 clear cell (C), 14 mucinous (M) and 5 mixed epithelial tumors, treated between 1/2006 and 12/2007 were analyzed. In 27 patients, only conventional cytology technique was performed; in 14 patients, cell block preparation method was also used. IHC staining of estrogen receptor (ER), mutant p53, cytokeratin 20 (CK20), vimentin and periodic acid-Schiff stain (PAS) was performed in the cytology and/or cell block specimens. Results: In conventional peritoneal cytology, the incidence of positive cytology was 63.0% (17/27). Adding cell block method and IHC staining increased the incidence of positive cytology (85.7%, 12/14). PAS was positive in 25% S (2/8), 33% E (3/9), 100% C (5/5) and 100% M (14/14); ER in 63% S (5/8), 100% E (9/9), 0% C (0/5) and 36% M (5/14); p53 in 75% S (6/8), 11% E (1/9), 0% C (0/5) and 0% M (0/14); Vimentin in 0% S (0/8), 100% E (9/9), 60% C (3/5) and 36% M (5/14); CK20 in 0% S (0/8), 0% E (0/9), 0% C (0/5) and 29% M (4/14). Using this IHC panel, the percentage of correct pretherapeutic diagnoses of histological subtype is 95.1% (39/41). Conclusions: Peritoneal cytology with cell block method and IHC staining of ER, p53 and PAS makes pretherapeutic diagnosis of histological subtype more accurate, and may be useful for individualizing treatment in advanced ovarian cancer patients. No significant financial relationships to disclose.