Wolffian Tumor of the Fallopian Tube Mimicking Malignant Adnexal Tumor: A Case Report and Literature Review

A 61-year-old woman was referred to our tertiary hospital after ultrasonography at a local clinic revealed a right adnexal mass with pelvic ascites. Her medical history included a laparoscopically assisted vaginal hysterectomy for uterine leiomyoma in 2012. Physical examination revealed no abnormalities, and laboratory test results, including complete blood count, serum electrolytes, and serum cancer antigen 125 (CA-125), were within normal limits. Transvaginal ultrasonography, including gray-scale and color Doppler imaging, was performed during the initial diagnostic workup. This revealed a 6.4 × 4.3 cm heterogeneous echogenic solid and cystic mass with peripheral calcification in the right adnexa. Doppler ultrasonography showed peripheral vascularity of the mass, with a small amount of pelvic ascites ( Fig. 1A ). Contrast-enhanced abdominopelvic CT demonstrated a 4.4 × 7.5 × 4.6 cm solid and cystic mass at the right adnexa ( Fig. 1B, C ). The lesion exhibited a central non-enhancing hypodense area, suggesting necrosis or cystic degeneration, and a peripherally enhancing solid component with curvilinear calcifications. A suspicious tiny peripheral fat attenuation focus was noted, a finding that was corroborated by pelvic MRI ( Fig. 2C ). However, no significant abdominopelvic lymphadenopathy or distant metastasis was observed. Pelvic MRI was performed using a 3T scanner (MAGNETOM Prisma Fit; Siemens Healthineers, Erlangen, Germany) for tumor evaluation. On pelvic MRI, the mass was located within an elongated tubular structure with internal folds that had T2 high-signal intensity (SI) ( Fig. 2A ), which seemed to be the dilated right fallopian tube; moreover, a suspected atrophied right ovary ( Fig. 2G, H ) abutted this presumed dilated fallopian tube. The mass demonstrated a central portion with T2 high SI ( Fig. 2A ) and T1 intermediate-to-slightly high SI ( Fig. 2B ) without enhancement ( Fig. 2D ), accompanied by a fluid-fluid level, suggesting necrosis or cystic degeneration. The enhanced peripheral solid portion of the mass ( Fig. 2D ) showed heterogeneous T2 high SI ( Fig. 2A ) and T1 intermediate SI ( Fig. 2B ), with intense enhancement ( Fig. 2D ), except for peripheral multifocal T1 and T2 low-SI foci ( Fig. 2A, B ) that correlated with calcifications on CT and peripheral multifocal T1 and T2 high-SI foci that exhibited fat suppression, which also appeared as calcifications on CT ( Fig. 1B, C ). A tiny T1 ( Fig. 2B ) and T2 ( Fig. 2A ) high-SI focus with fat suppression ( Fig. 2C ) was noted, corresponding to a suspected fat attenuation focus on CT ( Fig. 1B, C ). On diffusion-weighted imaging, most of the solid component of the mass exhibited no definite diffusion restriction ( Fig. 2E, F ), but some solid portions showed high SI at a high b-value (b = 1,000) and a low apparent diffusion coefficient (ADC) value (mean ADC: 0.977 × 10 -3 mm 2 /s), indicating moderate diffusion restriction ( Fig. 2G, H ). F-18 fluorodeoxyglucose (FDG) PET/CT revealed moderate FDG uptake in the peripheral solid portion of the tumor ( Supplementary Fig. 1 ), with no definite evidence of distant metastasis. Based on CT and MRI findings showing an intraluminal tubal mass with hydrosalpinx and moderate diffusion restriction in the enhancing solid component in a postmenopausal woman, a preoperative differential diagnosis of primary fallopian tube carcinoma was primarily considered despite normal CA-125 levels. However, additional features, such as peripheral calcification and a suspected fat component, which are uncommon in tubal carcinoma, raised the possibility of a mature tubal teratoma with malignant transformation. During bilateral salpingo-oophorectomy, a 9-cm right adnexal cyst exhibiting multifocal internal calcifications was identified. Peritoneal washing cytology was negative for malignancy. Upon opening the right salpinx, a yellowish-gray mass was observed protruding within the dilated lumen and adhering to the distal portion of the salpingeal wall. The cut surface showed a solid cystic tumor with hemorrhage, focal necrosis, and peripheral calcification. The atrophied right ovary was separated from the mass and abutted the dilated right fallopian tube ( Fig. 3A ). Microscopically, the tumor was composed of ovoid, cuboidal, and spindle-shaped cells arranged in diffuse solid and trabecular patterns, with occasional well-formed tubules. The tumor cells exhibited bland nuclei, scant cytoplasm, and rare mitotic figures. Metaplastic bone containing fatty marrow was present at the periphery of the tumor ( Fig. 3B ). Immunohistochemistry showed that the tumor cells were positive for CD10, cytokeratin 7, and pancytokeratin, but negative for PAX8 and GATA3. The final diagnosis was Wolffian tumor with ossification. Regarding correlations with pathology, the peripheral T1 and T2 low-SI foci on MRI that correlated with calcifications on CT were thought to be ossification. In addition, the peripheral multifocal T1 and T2 high-SI foci on MRI that showed fat suppression and appeared as calcifications and fat on CT were thought to be fatty marrow within the ossified region. Postoperatively, the patient underwent no additional treatment, such as hormone replacement therapy or adjuvant chemotherapy. A follow-up abdominopelvic CT scan seven months after surgery showed no evidence of local recurrence. This study was approved by the Institutional Review Board of Korea University Anam Hospital (IRB No. 2025AN0270), and the requirement for informed consent was waived.

Wolffian tumors are rare neoplasms that arise from Wolffian duct remnants and are also known as female adnexal tumors of probable Wolffian origin (FATWO). First described by Kariminejad and Scully in 1973 ( 1 ), these tumors were classified in the 2014 World Health Organization Classification of Tumors of Female Reproductive Organs ( 2 ). They may develop anywhere along the mesonephric duct remnants, including the ovarian hilum, mesosalpinx, lateral uterine wall, and outer vaginal third. Although the majority occur in the broad ligament, these tumors infrequently arise within the fallopian tube wall ( 2 3 4 ). Most Wolffian tumors follow a benign clinical course, but approximately 10%–20% exhibit aggressive behavior, including metastasis and recurrence ( 5 ). Owing to their rarity, no standardized treatment guidelines exist; however, surgical resection, typically hysterectomy with bilateral salpingo-oophorectomy, remains the primary approach ( 5 ). Imaging findings are limited to sporadic case reports owing to the rarity of the tumor. We report the case of a 61-year-old woman with a Wolffian tumor initially misdiagnosed as malignant tubal cancer based on atypical imaging findings. We also describe its ultrasonographic, CT, and MRI features.

Wolffian tumors are exceptionally rare neoplasms arising from Wolffian duct remnants and are also known as FATWO. First described by Kariminejad and Scully in 1973, these tumors were initially reported in nine cases as distinctive female adnexal masses originating from the broad ligament or pedunculated structures ( 1 6 ). In the 2014 World Health Organization Classification of Tumors of the Female Reproductive Organs, Wolffian tumors were formally recognized as a distinct entity ( 2 ). During embryogenesis, the Wolffian (mesonephric) duct typically regresses completely by the third embryonic month after the removal of the uterine component. However, persistent remnants, such as the epoophoron, paroophoron, and Gartner’s duct, may remain in adults. Consequently, Wolffian tumors may develop anywhere along the embryologic path of these ducts, including the ovarian hilum, mesosalpinx, lateral uterine wall, and distal vagina. Although most occur in the broad ligament, rare cases have been reported within the fallopian tube wall ( 1 2 3 4 ). Clinically, Wolffian tumors are often asymptomatic and discovered incidentally during gynecological evaluations. Patients may present with nonspecific abdominal symptoms, such as abdominal distension, pain, bloating, vaginal bleeding, or endocrine-related symptoms, when the tumor is sufficiently large. These tumors occur at comparable frequencies in reproductive-aged and postmenopausal women, with a mean diagnostic age of 50 years (range: 15–83 years). Reported tumor sizes range from 0.8 cm to 20 cm (mean size: 12 cm), and all cases described in the literature have been unilateral. Preoperative CA-125 levels are typically normal in Wolffian tumors ( 1 2 3 7 ). Owing to the rarity of Wolffian tumors and the challenges in establishing a definitive preoperative diagnosis, no standard treatment guidelines exist. Current practice favors complete surgical resection, including hysterectomy, bilateral salpingo-oophorectomy, and tumor debulking, as the primary therapeutic approach. Although most Wolffian tumors follow a benign course, approximately 10%–20% of cases exhibit aggressive behavior, including metastasis or recurrence. Therefore, these tumors are classified as having low malignant potential. When Wolffian tumors recur or metastasize, they are generally found in the broad ligament but have also been reported in the liver and lungs. The median time to recurrence was 48 months (range: 13–96 months), with some cases recurring long after the initial diagnosis. Given this risk, clinical follow-up is advised every 6 months for the first two years, followed by annual monitoring thereafter ( 2 5 8 ). Histologically, Wolffian tumors exhibit marked intratumoral and intertumoral heterogeneity and are characterized by diverse architectural patterns. These may include solid, tubular, or sieve-like arrangements, with rare trabecular or microcystic patterns. Diagnosis often relies on recognizing a combination of these diverse architectural patterns, which helps differentiate Wolffian tumors from other entities. Tumor cells are typically cuboidal, ovoid, or spindle-shaped, with minimal cytologic atypia and mitotic activity ( 1 2 3 4 ). Owing to their rarity, the imaging features of Wolffian tumors have been described in only a limited number of case reports and small series. On ultrasonography, these tumors frequently present as complex solid-cystic adnexal masses located separately from the ovary and are most commonly found in paravaginal, paraovarian, or retroperitoneal locations. Color Doppler findings vary significantly, ranging from a highly vascularized appearance to minimal or absent detectable blood flow ( 8 ). The characteristics of CT, MRI, and FDG-PET/CT were summarized by Ito et al. ( 3 ). Their findings indicated that Wolffian tumors demonstrate soft-tissue attenuation comparable to that of skeletal muscle on unenhanced CT, homogeneous enhancement similar to that of the myometrium on contrast-enhanced CT, and frequent cystic or necrotic components with curvilinear and punctate calcifications ( 3 ). On MRI, Wolffian tumors typically appear as well-circumscribed extraovarian masses with isointense signals relative to skeletal muscle on T1-weighted images, variable intermediate SI on T2-weighted images, and relatively homogeneous enhancement after contrast administration. Some cases have demonstrated central necrosis in Wolffian tumors. Sakai et al. ( 9 ) proposed that a thin, hypointense rim on T2-weighted images with strong enhancement, suggestive of a smooth muscle capsule, may represent a characteristic MRI feature. Wolffian tumors also show high SI on diffusion-weighted images with restricted ADC values, reflecting their hypercellularity and complicating differentiation from malignant lesions ( 3 5 7 9 ). Additionally, according to Ito et al. ( 3 ), even benign Wolffian tumors may demonstrate moderate FDG uptake on FDG-PET/CT, further complicating accurate preoperative diagnosis. In our case, the atypical imaging presentation, including an intraluminal tubal mass causing hydrosalpinx, peripheral calcifications, and fat foci, posed significant diagnostic challenges. To date, Wolffian tumors presenting as intraluminal tubal masses have not been documented in the literature, with only one case report demonstrating fat on MRI ( 7 ). To the best of our knowledge, this is the first reported case of a Wolffian tumor demonstrating ossification with fatty marrow on imaging. On MRI, these areas appeared as peripheral T1 and T2 hypointense foci corresponding to calcified areas on CT, which were pathologically confirmed as ossification. In addition, peripheral multifocal T1 and T2 hyperintense foci with signal loss on fat-suppressed images, which mimicked calcification and fat on CT, were pathologically confirmed to represent fatty marrow within the ossified component. Furthermore, the observed high T2-weighted SI in the solid component and extensive necrosis differ from the typical imaging features described in previous literature. In this case, the typical hypointense rim on T2-weighted images, previously regarded as a characteristic finding of Wolffian tumors, was not observed. The principal differential diagnoses for Wolffian tumors include solid adnexal tumors with cystic components, such as extraovarian tumors (e.g., subserosal or broad ligament leiomyoma), gastrointestinal stromal tumors, and ovarian tumors (e.g., granulosa cell tumors, fibroma-thecoma group, and Brenner’s tumors) ( 1 3 7 ). The differential diagnoses for the Wolffian tumors in our case were primary tubal carcinoma and tubal teratoma with malignant transformation. Although primary tubal carcinoma is typically associated with dilated fallopian tubes, it also demonstrates peritoneal implantation, elevated CA-125 levels, lower ADC values with marked diffusion restriction, and more avid FDG uptake, which were absent in our patient ( 3 ). Tubal teratomas with malignant transformation are extremely rare, with only a few case reports in the literature. Most tubal teratomas are intraluminal and are located in the isthmus and ampullary region of the fallopian tube. Histologically, tubal teratomas resemble their ovarian counterparts and commonly exhibit intratumoral fat and calcification, typically reflecting mature adipose tissue, sebaceous material, cartilage, or teeth ( 10 ). However, these features are distinct from the ossification with fatty marrow observed in the present case, highlighting the unique pathological nature of this Wolffian tumor. Additionally, tubal teratomas with malignant transformation may present as solid and cystic masses with moderate diffusion restriction or moderate FDG uptake in the solid portion, consistent with our imaging findings. In conclusion, Wolffian tumors are exceptionally rare adnexal tumors that often occur in extraovarian regions. To our knowledge, this is the first reported case presenting as an intraluminal tubal mass causing hydrosalpinx with ossification containing a fatty marrow. Because Wolffian tumors can exhibit imaging features that mimic malignancy, including diffusion restriction, moderate FDG uptake, and hydrosalpinx, as seen in our case, these tumors should be considered in the differential diagnosis when an extraovarian adnexal mass displays such features resembling malignancy but presents with normal CA-125 levels.