Discussion
Peritoneal washing cytology is a useful indicator of ovarian surface involvement and peritoneal dissemination by ovarian tumors. It may identify subclinical peritoneal spread and thus provide valuable staging and prognostic information [
4]. For the same reason, PWC was implemented in ovarian cancer guidelines and is routinely performed in ovarian cancer surgeries.
In our study, we report our experience of PWC with emphasis over its correlation with histological parameters, i.e., tumor type, tumor grade, tumor size, capsular invasion, and omental metastasis.
Cytology detection rates of abdominal spread in ovarian cancers vary in different studies. Fadare et al. reported 25 % and Rubin et al. reported 30 % detection rate, while Colgan et al. revealed 50 % detection rate [
5‐
7]. As much as 90 % positive cytology detection rate has also been reported in a study [
8]. This can be due to the inclusion of ascitic fluid along with peritoneal washings, as ascitic fluid has a much higher rate of detecting malignant cells.
In our observation, serous carcinomas (
n = 26.79 %) were most likely and mucinous carcinoma (
n = 8, 25 %) were least likely to involve abdominal cavity as represented by positive peritoneal cytology. Forty-four percent of endometrioid carcinoma (
n = 9), 100 % of clear cell carcinoma (
n = 1), 100 % of transitional cell carcinoma (
n = 1), 66 % of malignant mullerian tumors (
n = 3), and 50 % of germ cell tumors (
n = 2) showed positive cytology. Fadare et al. reported 71.4 % of serous carcinoma (
n = 57), 55 % of endometrioid carcinoma (
n = 30), 20 % of clear cell carcinoma (
n = 19), and 50 % of mucinous carcinoma (
n = 13) showing positive peritoneal cytology [
5]. Similar study by Rubin et al. analyzed 96 cases of ovarian tumors of which 29 cases showed positive PWC [
6]. The histological subtypes included the following: serous, 21 of 66 (32 %); endometrioid, 3 of 11 (27 %); mucinous 0 of 1 (0 %); and clear cell carcinoma, 2 of 3 (66 %).
In patients with ovarian serous tumor of low malignant potential and borderline tumors, PWC is a relatively sensitive indicator for presence of peritoneal implants whether invasive or non-invasive [
2]. Positive cytology upstages borderline tumors. Mulvany, in his study, concluded that the clinical value of PWC lies in upstaging 63 % of borderline ovarian tumors [
3]. Cheng et al. demonstrated a 44 % positive cytology detection rate of borderline mucinous tumors [
9]. However, in our study, there were only five borderline tumor cases (one serous, four mucinous). All showed negative cytology as well as no omental metastasis.
Omental metastasis/peritoneal histology are used as a standard to determine the sensitivity and specificity of PWC. In our study, 35 cases showed positive PWC and 31 showed omental metastasis. There were six cases (6/35; 17 %) that were cytology positive and histology negative. These included two serous carcinomas, two endometrioid carcinoma, one mucinous carcinoma, and one MMT. Out of 25 cytology negative cases, only two showed omental metastasis (2/25; 8 %), one serous, and one mucinous. Sneige et al., in their study, observed that 11/70 cases (16 %) were cytology positive and biopsy negative [
2]. In a study by Zuna and Behrens, 112 ovarian carcinoma cases were analyzed, and only three stage I cases had positive cytology and negative peritoneal histology (two carcinomas and one borderline tumor) [
10]. Of these, only patients with borderline tumors were alive at the last follow-up. Other two died of the disease. In one study, late recurrences were reported in patients with low-grade serous tumors having negative staging biopsy, and they concluded that this may be due to sampling error at the site of implant [
11]. Hence, stage I disease without omental metastasis but positive cytology may indicate increased risk of tumor recurrence, and this emphasizes the importance of PWC. In our study, the correlation of PWC with omental metastasis was statistically significant.
According to the recent Federation of Gynecology and Obstetrics (FIGO) guidelines, capsular rupture upstages a stage I tumor to stage IC2 and positive cytology to stage IC3 [
12]. Hence, determination of capsular integrity is important as this changes cancer stage. In our study, we tried to correlate capsular invasion with PWC. Out of 60 cases, 37 showed capsular invasion but not all showed positive cytology. Of cytology-positive cases, only 5 had capsule intact and out of 25 cytology negative cases, and 7 had capsular rupture. Of 26 serous carcinomas, 22 (84 %) showed capsular invasion while 20 (76.9 %) showed positive cytology. One borderline mucinous tumor had capsular invasion but a negative cytology. All three MMT showed ruptured capsule (invasion) with two showing positive PWC. Only one case (endometrioid carcinoma) showed positive cytology with intact capsule. With or without capsular invasion, the presence of PWC in stage I disease alone is sufficient to upgrade the tumor. We observed a strong correlation between capsular invasion and PWC (
p = <0.001).
In our study, the mean tumor size was different for different tumor types. It was 11.58 cm for serous tumors, 6.5 cm for endometrioid tumors, and 22 cm for mucinous neoplasms. The largest tumor size was 30 cm of mucinous carcinoma. Positive peritoneal cytology was correlated to tumor size, and we observed that most of the positive cytology cases had tumor size of less than 10 cm (28/35 cases, 84 %) and only one tumor of more than 20 cm showed positive cytology. Interestingly, most (7/8) large tumors (>20 cm) had negative cytology. Of these, only one showed omental metastasis, i.e., histology positive. The rest had intact capsules and no omental metastasis. All large tumors were mucinous. The only large tumor with positive cytology was 30 cm in size with capsular invasion and omental metastasis. We observed that mucinous tumors may acquire large sizes but mostly remain organ confined with negative cytology. Some of the intermediate sized serous tumors also showed negative cytology. Hence, smaller tumors have a significantly more incidence of positive PWC.
Tumor grade also had an impact on abdominal spread of ovarian tumors. We found out that 30 out of the 35 cytology-positive cases had high histological grade, four had intermediate grade, and only one had low grade. Fifteen (33 %) of high-grade tumors showed negative histology. Ozkara reported that PW were significantly more likely to yield malignant cells in higher grade than lower grade tumors [
13].
Competing interest
The authors declare that they have no competing interests.
Authors’ contributions
SN, AAA, and RA were the clinical investigators of this study. AAA, SDH, and MME analyzed the data and wrote the manuscript, NF and MK critically revised it. All authors read and approved the final manuscript.