Gynaecological malignancies are the most prevalent and lethal form of cancer amongst women in the world. Of these, ovarian carcinoma is the deadliest accounting for more than 14,000 deaths per year. Since there are no established way of prevention or screening for it, many of the ovarian cancer cases are diagnosed as International Federation of Gynaecology and Obstetrics (FIGO) stage III or higher.[1]In recent years, it has become clear that many pelvic high-grade serous carcinomas (including ovarian, fallopian tube and primary peritoneal carcinomas) are preceded by a precursor lesion in the distal fallopian tube. These precursors range from small self-limited p53 signatures to expansile serous tubal intraepithelial neoplasms that include both serous tubal intraepithelial lesions in transition (STILT) of uncertain significance and serous tubal intraepithelial carcinomas (STICs). STIC is the earliest recognisable lesion in the pathogenesis of various pelvic serous carcinomas and has cellular features similar to that of high-grade serous carcinomas (HG-SCs).[2]STIC has been implicated in patients with BRCA1/2 mutations undergoing risk-reducing bilateral salpingo-oophorectomy at a young age in 3.5 to 5.5% of cases.[3] Hence, proper screening methods are required to detect early precursor lesions at younger age.

To maximise the detection of precursor lesions in the fallopian tubes in patients at risk of ovarian cancer, the protocol for Sectioning and Extensively Examining the FIMbria (SEE-FIM) has been established by Medeiros et al. [4] Examination of prophylactically removed fallopian tubes has shown STIC in the fimbriated end in 57% and 100% cases. [5-9] Fascinatingly, 47% of the tumours classified as ovarian serous carcinomas coexisted with STIC as reported by Kindelberger et al. [10]

Since STIC is implicated in pathogenesis of HGSCs, it can be hypothesized that the incidence of STIC should be lower in other types of gynaecological malignancies and benign gynaecological neoplasms. Therefore, this study has been taken up to evaluate the role of STIC in pelvic serous carcinogenesis and to assess the frequency of incidence of STIC in pelvic serous carcinomas, endometrial serous carcinomas, other non-serous gynecological malignancies and benign gynecological neoplasms and to statistically compare the significance of its occurrence in all these conditions.

The study was conducted in the Department of Pathology and Department of Gynaecology, SCB Medical College and Hospital, Cuttack, and Department of Gynaecological Oncology, AHPGIC, Cuttack from the period of February 2020 to January 2023 with the approval of Institutional Ethics Committee, SCB Medical College, Cuttack (IEC Application no.- 148 dated 07.02.2020).

Inclusion criteria- All histopathologically diagnosed female patients of gynaecological neoplasms irrespective of age were included in the study.

Exclusion criteria-

1. Treated cases of gynaecological malignancies
2. Patients unwilling to give consent
3. Inadequately fixed and autolysed specimens
4. Neoplasms of vagina and vulva were excluded as these undergo local excision and do not require salpingectomy

Ultimately 176 consecutive cases that fulfilled the above criteria were taken up for the study. Tumour typing was done according to WHO 2020 Classification and tumours were staged according to FIGO Staging, 2018. After taking proper consent, both side fallopian tubes of patients diagnosed with benign and malignant gynaecological neoplasms were collected and submitted for grossing. Grossing of the tubal specimens was done according to “SEE-FIM” Protocol. The whole tube was fixed in 10% formalin for a minimum duration of 4 hours, in order to reduce the risk of deterioration of the epithelium.

1. Multiple longitudinal sections of the distal 2cm of the fimbriated end of the tube were taken (usually into 4 parts).
2. Serial transverse sections (every 2-3mm) were taken from the remaining entire length of the fallopian tube.

This was followed by extensive histopathological examination of the whole tube to note for presence of serous intratubular lesions including p553 signature, STIL and STIC. Further, all these blocks were subjected to IHC for p53 and Ki-67 to confirm the presence or absence of these lesions.

Statistical analysis-The results of immunohistochemistry were noted down in tabular form. The number of cases in each category were also expressed in the form of percentage. The statistical significance of this categorical data was assessed using SPSS (Statistical Package for Social Sciences version 21) software. The categorical variables were compared by means of Chi-square test to find out association between the different variables. P-value was calculated statistically and a P-value of <0.05 was considered significant.

The present study was done on 176 cases of gynaecological neoplasms out of which 104 (59.1%) cases were benign and 72 (40.9%) cases were malignant. Of the 176 cases, there were 29 (16.5%) cases of high- grade serous carcinoma of ovary, 2 (1.15%) cases of tubal serous carcinoma, 2 (1.15%) cases of primary peritoneal carcinoma, 5 (2.8%) cases of serous carcinoma of endometrium, 34 (19.3%) cases of other non-serous gynaecological malignancies and 104 (59.1%) cases of benign gynaecological neoplasms comprising of majority of ovarian origin (55=352.88%) followed by those of uterine origin (37=35.57%)

 The highest number of cases amongst the benign neoplasms were found in 6^th decade (40.4%) followed by 5^th decade (15.4%). Amongst the malignant neoplasms, the maximum number of cases were found in the 7^th decade (30.6%) followed by 6^th decade (27.8%). Thus, out of 26 cases showing precursor lesions at the fimbriated end of the fallopian tube, 9 (34.6%) cases belonged to the age group of 51-60 years. Only 6 (5.76%) out of 104 cases had family history of breast/ovarian carcinoma whereas 54 (75%) out of 72 cases of gynaecological malignancies had family history of breast/ovarian malignancies.

Above study revealed that among 29 HGSC of ovary, the presence of p53 signature, STILT and STIC were noted in 7 (24%), 5 (17.2%) and 9 (31%) cases respectively. One (50%) out of 2 cases of primary tubal carcinoma showed the presence of STIC. Out of 2 cases of primary peritoneal carcinoma, 1 (50%) case showed the presence of p53 signature and 1 case (50%) showed the presence of STIC. One (20%) out of 5 cases of serous carcinoma of endometrium showed the presence of p53 signature and one (33.3%) out of 3 cases of borderline serous tumour of ovary showed presence of STILT. Other non-serous gynaecological malignancies and benign gynaecological neoplasms did not show evidence of any precursor lesion in fallopian tube. It was seen that STIC was significantly associated with high-grade pelvic serous carcinoma as none of the non-serous gynaecological malignancies and benign gynaecological neoplasms showed presence of STIC. (P value-0.045)

Most of the gynaecological malignancies were histologically high-grade (50 cases, 69.4%) and majority of these carcinomas belonged to FIGO stage II and III (61%) followed by FIGO stage IV. Correlating the tumour grade with presence of STIC, STIC was found in high-grade tumours only (11 out of 50 cases- 22%) which was statistically significant as none of the low-grade tumours (0 out of 22 cases) showed presence of STIC. (P value -0.0427) Similarly correlating STIC with tumour stage, it was found that majority of STIC was seen in FIGO stage III/IV (6 out of 22 cases in stage III- 27.3% and 2 out of 15 cases in stage IV- 13.3%) which was statistically not significant. (p value- 0.0694).

TABLES:

TABLE 1: Distribution of type of neoplasm and its site:

TABLE 2: Distribution of various tubal intra-epithelial lesions-

TABLE 3: Correlation of histologic type of tumour with presence of STIC

TABLE 4: Correlation of histological grade and stage of tumour with presence of STIC-

FIGURE LEGENDS:

Figure 1- High Grade Papillary serous carcinoma of ovary (a). Gross picture showing uterus with bilateral Ovarian masses, (b.) H & E 400X- Microsection shows features of Papillary High Grade Ovarian Serous Carcinoma, (c.) H & E, 400X - Tubal epithelium showing foci of STIC, (d. )STIC - IHC showing Diffuse intense nuclear p53 immunostaining in > 75% cells. (e.)  “STIC” IHC for Ki-67 positive in > 10% cells

Figure 2- Papillary serous carcinoma of endometrium, a) Gross picture showing presence of an uterine growth with papillary excrescences, b) H& E 400 X Microsection shows features of Papillary serous carcinoma of endometrium, (c.) H & E,400X- Fimbriated end of the fallopian tube showing loss of ciliated cells without any atypia. “ p53 signature”  (d.) “ p53 signature” – IHC for p53 positivity seen in >12 consecutive epithelial   cells. (e) p53 signature IHC for Ki-67- Low Ki-67 index (<10 % of cells).

Figure 3 Squamous cell carcinoma of cervix (keratinising type), (a) Gross picture showing presence of an ectocervical growth (b) H & E 400X, Microsection shows features of squamous cell carcinoma,, keratinising type, (c) Normal tubal epithelial lining (d) P53 immunostaining negative for STIC (e) Ki-67 immunostaining index <5%

Pelvic HGSCs comprise a lethal malignant condition contributing to significant mortality and morbidity. The culprit has been assumed to be late detection of this malignancy due to lack of a proper screening procedure. This has led to discovery of the precursor cancerours lesion in fimbrial end of fallopian tube in ovarian, primary peritoneal and tubal serous carcinomas. Finding of tubal intraepithelial lesions/ carcinoma in prophylactic salpingectomies in women with BRCA mutations (BRCA+) have pointed the tubes as a frequent source of early serous carcinoma. Kindelberger et al.  reported that primary ovarian serous carcinomas often involve the endosalpinx, and many of these contain STIC.[10] But an important scenario is that many HGSCs are not associated with this precancerous lesions in tubes. Also, the coexistence of tubal intraepithelial carcinoma has been found in many non-serous gynecological malignancies. Also, the association of STIC with other gynaecological malignancies has  remained controversial in few studies. Tolcher M et al studied 38 cases of endometrial serous carcinomas of which only 2 cases showed presence of STIC. [11] Most authors have concluded that that these STICs could be metastatic implants from a higher stage of these carcinomas. Als, another question remails to be answered -Whether these represent synchronous multifocal lesions, metastases or primary site origin ?

Hence, we hypothesize that in this background the occurrence of STIC and allied lesions should be significantly less in other gynecological malignancies and benign gynecological neoplasms. Therefore, this study was carried out to find out the incidence of precancerous tubal intraepithelial pathologies in pelvic serous carcinomas, other gynecological malignancies and benign gynecological neoplasms.

Present study revealed the presence of p53 signature, STILT and STIC in 7 (24%), 5 (17.2%) and 9 (31%) cases respectively, out of 29 HGSC of ovary. One (50%) out of 2 cases of primary tubal carcinoma showed the presence of STIC. Out of 2 cases of primary peritoneal carcinoma, 1 (50%) case showed the presence of p53 signature and 1 case (50%) showed the presence of STIC. 1 case (20%) out of 5 cases of serous carcinoma of endometrium showed presence of p53 signature and 1 case (33.3%) out of 3 cases of borderline serous tumour of ovary showed the presence of TILT. Other gynaecological malignancies and benign gynaecological neoplasms did not show evidence of any precursor lesion in the fallopian tube. (Table 2). Our finding was consistent with that of Tang Shaanguo[12] et al who studied 300 cases of gynaecological neoplasms and found that STIC was present in 6 cases (18.8%) out of 32 cases of ovarian serous carcinoma, 2 cases (28.6%) out of 7 cases of primary peritoneal carcinoma and 4 cases (14.3%) out of 28 cases of endometrial serous carcinoma but did not find any evidence of STIC in non-serous gynaecological malignancies and benign gynaecological neoplasms. Tewari S et al analysed fallopian tubes in 100 cases of benign disease by correlation of H&E stain and IHC. After IHC confirmation, SCOUTS were detected in 45% of the cases, p53 signature in 2%, STIL in 9%, and STIC in 4%.[13] Nermin K [14] et al studied 495 cases of gynaecological neoplasms and found that STIC was present in 9 cases (36%) out of 25 cases of HGSCs of ovary, 3 (50%) out of 6 cases of primary serous tubal carcinoma and 1 (33%) out of 3 cases of primary peritoneal carcinoma and did not find any evidence of STIC in endometrial serous carcinoma, non-serous gynaecological malignancies and benign gynaecological neoplasms. , Correlating tumour grade with the presence of STIC, all the 11 cases of STIC were seen in high-grade pelvic serous carcinomas which was statistically significant as none of the low-grade tumours showed evidence of STIC. (Table 4). Our finding was supported by Tang Shaanguo[12] et al who also found STIC existing in 12 out of 67 cases of high-grade serous malignancies and in none of the low-grade malignancies. Correlating the tumour stage with the presence of STIC in the present study (Table 5), it was found that 6 cases (27.3%) out of 22 cases in Stage III contained STIC. Similarly, 2 cases (13.3%) out of 15 cases in stage IV contained STIC. Two cases (9%) out of 22 cases in stage II contained STIC. 1 case (7.7%) out of 13 cases present in stage I contained STIC. This was statistically not significant. (p value= 0.0694). Seidman JD [15] et al found that patients with STIC were significantly more likely to have FIGO stage IV as compared to those without STIC (42% vs. 12.5% respectively; p=0.037). Nermin K [14] et al also found that all the 13 cases of STIC belonged to FIGO stage II/III pelvic serous carcinomas, which goes well with our study.

In conclusion, in current study STIC was present in 11 out of 33 (33.3%) cases of high-grade pelvic serous carcinomas (highly significant) and in none of the non-serous gynaecological malignancies and benign gynaecological neoplasms which correlated well with various studies mentioned above. Therefore, STIC is proved to be one of the etiology of pelvic HGSCs and its incidence is substantially lower in other non-serous gynaecological malignancies and benign gynaecological neoplasms. Other theories of etiology of pelvic serous carcinoma are hypothesized to be surface epithelial inclusion

Based on the results of this study and several other studies in the literature, it can be concluded that STIC acts as a precursor lesion in many cases of high-grade pelvic serous carcinomas (including ovarian, fallopian tube and primary peritoneal). Association of STIC with serous carcinoma of endometrium is still unclear. STIC is not usually associated with any other gynaecological malignancies and benign gynaecological neoplasms. As we move forward with advancing our understanding of the clinical-pathologic associations of this lesion, it is important that we carefully incorporate this finding into future clinical management algorithms.

Thus, prophylactic salpingectomy while performing hysterectomy and doing fimbriectomy as opposed to tubal ligation for tubal sterilisation can be adopted as screening and preventive methods for these lethal entities.

Limitations: BRCA mutation study is not undertaken during this study

Less number of cases is another limitation

Conflict of interest: There is no conflict of interest

Funding sources: The authors declare that there is no funding taken from outside sources Authors’ contribution details: Dr. Asaranti Kar- Conception & design, case collection, intellectual content, revising critically

Dr. Akruti Mishra- Data analysis, case collection, intellectual content, drafting

Dr. Pranati Mohanty- Conception, data analysis, drafting, reading & revising the manuscript

Dr. Bhagyalaxmi Nayak- Case collection, data analysis, reading & revising the manuscript

Dr. Tushar Kar- Conception, case collection, redaing & revising the manuscript

All authors have critically analysed the article & agreed to the final version of the manuscript to be published.

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