Clinical and ultrasound characteristics of primary fallopian tube carcinoma: a single-institution retrospective study of 280 cases

Primary carcinoma of the fallopian tube is one of the rarest gynecological malignancies, accounting for 0.7–1.5 cases of all malignant neoplasms per 100,000 women [1, 2]. However, the prevalence of primary tubal carcinoma is likely underestimated since many advanced cases are misdiagnosed as ovarian cancer [3]. Over the years, the incidence of fallopian tube carcinoma has increased almost fourfold in the USA (from 0.19 to 0.63), with a corresponding decrease in ovarian incidence from 5.31 to 4.86 [4]. This can be attributed to a better understanding of the pathology and improved diagnostic techniques [5]. There are several histological types of fallopian tube carcinomas, similar to their ovarian counterparts, the most common variant of which is serous papillary carcinoma [6‐8]. The etiology remains unknown. In recent years, there has been increasing evidence that serous tubal intraepithelial carcinoma most often occurs at the fimbriated end of the fallopian tube and is the progenitor of many serous adenocarcinomas previously thought to originate from the ovaries [5]. With subsequent progression, isolated serous tubal intraepithelial carcinoma may implant on the ovary and other extrauterine parts and develop into high-grade serous carcinoma. Most fallopian tube carcinomas are discovered in late phases, which makes them difficult to distinguish from ovarian malignant tumors or metastatic fallopian carcinomas.

Most women with symptomatic tumors are between 50 and 80 years of age, with the mean age reported in large studies ranging from 56–64 years [9, 10]. Some patients have synchronous tumors of breast carcinoma or carcinoma at other gynecologic sites, especially those with BRCA1/2 mutations [11]. Primary fallopian tube carcinomas usually occur more commonly in nulliparous, postmenopausal women [10]. Most (87–97%) cases of fallopian tube carcinoma are unilateral. [2, 6, 9, 10]. The average tumor size is 4–5 cm [2, 9]. Intraepithelial carcinoma and small tumors with microscopic invasion are usually asymptomatic and are more commonly seen as occult findings in prophylactic bilateral salpingo-oophorectomy specimens or rarely seen as occult findings in routine specimens. Patients report symptoms such as abdominal pain, vaginal discharge, an abdominal/pelvic mass, abdominal distension, loss of weight and/or appetite, and bowel and bladder symptoms [12]. Serum CA125 is elevated in most but not all patients. Because of the rarity of fallopian tube carcinoma (prior classification), as well as the clinical presentation that simulates an ovarian tumor, a correct preoperative diagnosis of fallopian tube carcinoma is uncommon.

The treatment of fallopian tube carcinoma is similar to that of ovarian and primary peritoneal malignancies due to similarity in their clinical behavior. NCCN recommends that patients with primary fallopian tube carcinoma receive cytoreductive surgery combined with carboplatin paclitaxel chemotherapy [13]. In a large clinicopathologic study of hospital-based cases, the 5-year survival rates were as follows: stage 0 (88%) [old staging system], stage 1 (73%), stage 2 (37%), stage 3 (29%), and stage 4 (12%) [6]. The overall 5-year survival of patients with fallopian tube carcinoma has increased since 2002. The five-year cause-specific survival rate is 97.9% for fallopian tube carcinoma in situ and 83.2% for early-stage high-grade serous tubal carcinoma [14].

Ultrasound diagnosis is a common auxiliary method for gynecological diseases and is important for early screening of malignant tumors. However, its sensitivity in detecting primary tubal carcinoma is low, and differentiating it from epithelial ovarian cancer is difficult. With the increasing diagnostic rate, there is a need to summarize the clinical and ultrasound features of fallopian tube carcinoma on the basis of a larger sample size to improve early diagnosis. This study aimed to reevaluate the clinical and sonographic characteristics of primary fallopian tube cancer patients under updated pathological criteria using a large sample from a single center. By systematically analyzing these features, we seek a deeper understanding of the disease and aim to offer more references for preoperative screening.

Participants Patients who underwent chemotherapy before the ultrasound exam and pathologic exams were excluded. Patients diagnosed with serous tubal intraepithelial carcinoma via pathology were excluded since the lesion might be too small to be distinguishable via ultrasound examination. Patients who had undergone salpingectomy before the ultrasound exam were excluded. Each of the patients had undergone preoperative ultrasound examination by an experienced ultrasound examiner via a standardized examination technique. If needed, transabdominal ultrasound was also performed. The ultrasound images were reviewed retrospectively by another experienced examiner with expertise in diagnosing gynecological neoplasms. All patients were examined via transvaginal ultrasound supplemented with a transabdominal scan if necessary. All the examinations were carried out via high-end ultrasound equipment, namely, a GE Volusion E6, Mindray R9, Philips HD11, with the frequency of the vaginal probes varying from 5.0–9.0 MHz and that of the abdominal probes ranging from 1.0–6.0 MHz. The patient's age, menopausal status, reproductive history, personal and family history of malignant tumors, chief complaints, serum CA125 level and pathological diagnosis were extracted from medical history information. All patients provided signed consent for the use of their medical records in potential clinical studies. The project was reviewed and approved by the ethical committee of Obstetrics and Gynecology Hospital (OB2024–191) in accordance with the principles of the Helsinki Declaration. Semiquantitative analysis (grades 0–3) [15] was used to assess the blood flow within the lesion on color Doppler images. The accuracy of ultrasound diagnosis was evaluated on the basis of the consistency between the major lesions identified in the ultrasound report and the findings from intraoperative exploration.

Two hundred eighty patients were identified under the screening criterion. The clinical background data are shown in Table 1. The median age of the study population was 58 years, with an interquartile range (IQR) of 52–66 years. Out of a total of 280 patients, 214 (76.43%) were postmenopausal. The majority of the participants, 269 out of 280 (96.07%), had given birth. Ten (3.57%) of the 280 patients had a concurrent breast cancer diagnosis. Similarly, 10 patients (3.57%) had a synchronous diagnosis of other malignancies. Twelve individuals (4.29%) had a family history of breast cancer. Only 1 patient (0.36%) had a family history of endometrial cancer. Twelve patients (4.29%) reported a family history of ovarian cancer. Forty-nine patients (17.5%) had a family history of other malignancies. The main complaints reported by the patients were diverse: the most common was abdominal pain and/or bloating, experienced by 100 patients (35.71%). Vaginal discharge was reported by 58 patients (20.71%), menstrual disorders were reported by 4 patients (1.43%), and notably, 118 patients (42.14%) were asymptomatic. A total of 82.79% (202/244) of the patients reported elevated CA125 levels. The median CA125 level was 208.4 U/mL in all patients, with the interquartile range ranging from 53.65 to 634.7 U/mL. Among all patients, CA125 levels were lower in patients with lesions confined mainly to the fallopian tube (91.8, P25–P75, 24.0–390.9) than in those with lesions located mainly beyond the fallopian tube (363.0, P25–P75, 117.0–1000). The predominant histological type was high-grade serous, accounting for 267 cases (95.36%) out of 280. Other rare histological types included adenocarcinoma (7 cases, 2.50%), carcinosarcoma (6 cases, 2.14%), clear cell carcinoma (1 case, 0.36%), and endometrioid (1 case, 0.36%). Confirmed by intraoperative observation, the majority of the masses were unilateral and were observed in 132 out of 280 patients (47.14%). Bilateral masses were present in 88 patients (31.43%), whereas abdominal masses with no exact laterality were noted in 54 patients (19.29%). No apparent dominant mass was found in 6 patients (2.14%), and only military nodules were observed in the peritoneum or surface of the pelvic organs. Intraoperative observation revealed that the major mass was located on the ovary in 141 patients (50.36%). In 108 patients (38.57%), the mass was reported to be located mainly on the fallopian tube. Pelvic/abdominal massive masses were present in 22 patients (7.86%), and 6 patients (2.14%) had other distributions, including concurrent major ovary and fallopian tube distributions. In the remaining 3 patients, no major mass was found intraoperatively (1.07%).

Table 2 describes the sonographic features of the masses examined by ultrasound. Six patients with no obvious neoplastic lesions were excluded from the analysis. These included (1) one case erroneously diagnosed as benign uterine fibroids; (2) two cases confirmed as simple pelvic effusion; (3) two cases exhibiting concurrent uterine cavity effusion and pelvic effusion; and (4) one case presenting endometrial abnormalities, with postoperative histopathology confirming tubal cancer invading the endometrium. In all cases where only pelvic and/or intrauterine effusion was detected, postoperative pathological examination consistently revealed widespread miliary lesions distributed throughout the pelvic cavity, indicating the absence of ultrasonographically discernible dominant lesions.

In the remaining 274 cases, echo type analysis revealed that solid masses were the most common, as observed in 126 cases (45.99%). Another portion of the solid masses was present in 100 patients (36.50%). Cystic masses were rare and were observed in only 1 patient (0.36%), and mainly cystic masses were found in 47 patients (17.15%). The median maximum diameter of the masses was 59 mm, with an IQR of 43–81 mm. For masses located mainly on the fallopian tube, the median maximum diameter was 50 mm, with an IQR of 38–66 mm. For masses located mainly on the ovaries, the median maximum diameter was 71.0 mm, with an IQR of 51–90 mm. The morphology of the mass on sonography revealed three typical patterns (Fig. 1): “classic” sausage shape (Fig. 1A–C), ovoid shape (Fig. 1D–F) and irregular shape (Figure G-H). Among the 274 cases, oval masses were the most prevalent and were observed in 157 cases (58.15%). Sausage-shaped masses were rare, observed in 22 patients (8.15%), and irregularly shaped masses were present in 91 patients (33.70%). Vascularity results via color Doppler revealed that Alder grade G3 was the most common, present in 185 patients (69.29%). Grades G2 and G1 were equally common in the remaining 82 patients (41% and 15.36%, respectively). No patient had a vascularity grade of G0. In 80 out of 280 patients (28.57%), the presence of endometrial fluid was observed. Considering the consistency between the ultrasound report and the findings from intraoperative exploration and postoperative pathology, 184 out of 274 cases (67.15%) were accurately diagnosed by the examiners, whereas in 90 cases (32.85%), the diagnosis was considered inaccurate.

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To further understand the different clinical characteristics of lesions distributed in different locations, we analyzed the CA125 levels and maximum lesion diameter between patients with predominantly ovarian lesions and those with fallopian tube lesions (Fig. 2). The results demonstrated that primary fallopian tube carcinoma lesions were located predominantly in ovarian tissues rather than in the fallopian tubes themselves. Compared with their tubal-predominant counterparts, ovarian-dominant tumors presented significantly greater serum CA125 levels (median 366.00 U/mL vs 90.98 U/mL, p < 0.0001, Mann‒Whitney U test) and larger lesion diameters (median 71.00 mm vs 50.50 mm, p < 0.0001, Mann‒Whitney U test).

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The sample size of this study is relatively large compared with that of previous reports. All ultrasound examinations were performed by expert sonographers, and all samples and data were obtained and reviewed within our hospital, which is a tertiary referral center with expert pathologists and clinicians. However, the limitations of this study are obvious. First, the data were sourced from a single research center. Consequently, these findings necessitate further validation via multicenter and large-scale sample studies. Second, the retrospective nature of the study imposes restrictions. Furthermore, the subjective judgment of examiners in categorizing lesion morphology patterns and the variability in imaging slice selection can affect and introduce errors in lesion shape assessment. The research conclusions should be cautiously generalized.

Nearly half of the cases of primary tubal carcinoma are asymptomatic. Abdominal pain/bloating was the most common complaint in the remaining patients. High-grade serous carcinoma was the predominant histological type. Unilateral, oval masses and high vascularization (grade 3) are the most prevalent ultrasonic features. Endometrial fluid was observed in nearly 1/3 of the patients. In primary tubal carcinoma, ovarian-dominant masses have significantly greater CA125 levels and larger diameters than do tubal-dominant masses.