Disseminated Actinomyces Case Report: A Mimicker of Advanced Ovarian Malignancy

Ovarian cancer (OC) accounts for 2.5% of all female cancers but is the fifth most common cause of cancer deaths in females. Over 12,700 women will die of OC in 2024 [1]. There are few early signs or symptoms of OC, and the majority of patients present with advanced disease. Due to diagnoses at stage III or IV, the 5-year survival rate is only 50% [1]. For women in whom OC is suspected, further evaluation with imaging and tumor markers is warranted. CA-125 can be helpful in identifying epithelial OCs and is elevated in half of patients with stage I disease and 90% of patients with advanced disease. Transvaginal ultrasonography may be the initial imaging modality to evaluate the ovaries and can reliably categorize an ovarian mass’ malignant potential. Suspicious masses can be further evaluated with magnetic resonance imaging or computerized tomography (CT) [2]. Screening for OC has not improved survival, and no screening tests are currently recommended [1].

Malignant ovarian tumors are characterized on magnetic resonance imaging by mixed solid and cystic components with areas of enhancement and necrosis [3]. CT findings of large volume ascites, enlarged lymph nodes, omental caking, and peritoneal implants in the setting of an ovarian mass are characteristic of OC, and specific CT imaging characteristics may predict unresectability [3, 4]. Several different disease processes can mimic ovarian malignancies. Benign ovarian masses, such as teratomas and endometriomas, and infectious etiologies, including tubo-ovarian abscesses, can appear similarly to OC on some imaging modalities [5]. Herein we present a case of actinomyces masquerading as OC. The CARE Checklist has been completed by the authors for this case report and is attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000540798).

A 55-year-old woman presented to the emergency department with 1 week of abdominal pain. She reported increasing abdominal girth and amenorrhea for the past 5 months. Evaluation in the emergency department revealed a 20-week-sized uterus, leukocytosis to 15.95 K/μL and anemia with a hemoglobin of 8.8 g/dL. Imaging findings were concerning for advanced malignancy (Fig. 1). Further assessment by a gynecologic oncologist was recommended, and she was referred for outpatient evaluation.

Additional clinical evaluation included an endometrial biopsy and a transvaginal ultrasound. The ultrasound revealed a complex right adnexal mass with high vascularity, concerning for malignancy. The endometrial biopsy resulted as benign endometrium with actinomyces granules observed. Tumor markers were notable for an elevated CA-125 (247.2 U/mL) and normal CEA (<0.5 ng/mL) and CA 19-9 (5.1 U/mL). The patient had a past medical history significant for hypertension well controlled on multiple medications (amlodipine, hydralazine, hydrochlorothiazide, metoprolol, and lisinopril), and a fibroid uterus with no significant symptoms. She had a copper intrauterine device (IUD) placed 10 years prior to presentation which was removed prior to the endometrial biopsy.

Based on imaging and laboratory findings, an ovarian malignancy was suspected. She was counseled on surgical management and consented for a diagnostic laparoscopy with possible OC debulking. At the time of diagnostic laparoscopy, a copious amount of purulent, malodorous peritoneal fluid was noted. Loculations of purulent material were seen throughout the abdomen and pelvis with aggregates of inflammatory tissue. The ovaries contained abscesses, were densely adherent to the posterior uterus and were necrotic in appearance. In order to achieve source control and rule out malignancy, an exploratory laparotomy, total hysterectomy, bilateral salpingo-oophorectomy, omentectomy, pelvic peritonectomy, and abdominal washout were performed. No peritoneal tumor implants or omental caking were appreciated at the time of surgery.

Histopathological examination revealed multiple abscesses with scattered aggregates of actinomyces (Fig. 2) and sulfur granules, as is characteristic of pelvic actinomyces [6]. The uterus, fallopian tubes, and ovaries were also noted to contain abscesses. No malignancy was seen, and she was diagnosed with disseminated actinomyces.

Her postoperative course was complicated by an intensive care unit admission secondary to sepsis. She recovered with resuscitation and intravenous (IV) antibiotics. Infectious disease was consulted for assistance with antibiotic management, and she was discharged home on postoperative day 14 on IV penicillin for 4 weeks followed by 6 months of oral antibiotics.

Actinomyces is a slow-growing gram negative, anerobic bacteria. It is a commensal organism of the oropharyngeal, gastrointestinal, and genitourinary tracts and is most commonly associated with oropharyngeal infections [7, 8]. The second most common site of infection is the genitourinary tract [9]. Despite this, little epidemiologic data are available regarding the incidence of pelvic actinomycosis, and the vast majority of data on these infections is published in case reports. Through review of these case reports, several factors have been associated with pelvic actinomycosis including the use of an IUD [10].

Commonly reported symptoms of pelvic actinomyces include weight loss, nonspecific abdominal or pelvic pain, and abnormal uterine bleeding [9, 11]. The physical exam is often benign but can include a yellow, foul-smelling vaginal discharge [8, 9]. Bloodwork is often nonspecific and can include leukocytosis and elevated inflammatory markers [11]. Mildly elevated tumor markers have also been reported, with elevated CA-125 and CA-15-3 being the most common [9]. Actinomyces can be very difficult to identify with imaging and can mimic malignancy. The diagnosis is usually made with histology and/or microbiology culture, either from Pap smear cytology or from intraoperative sampling [9].

Several case studies describe misdiagnosis of actinomycosis as malignancy, with the subsequent diagnosis of actinomyces made pathologically [12, 13]. Over 60% of cases of pelvic actinomycosis present with “tumor-like” symptoms, but only 10% of cases are correctly diagnosed preoperatively [10]. The recommended treatment for disseminated actinomyces infection is a long antibiotic course, typically IV penicillin for 2 to 6 weeks followed by oral penicillin for 6 to 12 months [8]. If diagnosed clinically by biopsy or culture, surgery is typically reserved for cases that do not respond to antibiotics, and minimally invasive drainage of abscesses may be considered.

In the patient described in this report, actinomyces was diagnosed by histopathology of the surgically obtained specimen. Preoperative CT imaging and pelvic ultrasound were unable to differentiate between malignancy and infection. Our patient did not have overt symptoms of infection and the elevated CA-125 helped support our suspicion for ovarian malignancy. The actinomycetes found on the preoperative endometrial biopsy was of unclear significance at that time, as 0.26% percent of Pap smears are incidentally positive for actinomyces [14]. Additionally, actinomyces-like organisms can be cultured in vaginal and cervical samples in up to 27% women and their presence is considered incidental even in the presence of an IUD [15]. Following the diagnosis of pelvic actinomycosis, the patient was treated with a long course of antibiotics.

In conclusion, pelvic actinomycosis can mimic ovarian malignancy, and the true diagnosis is often only elucidated when surgery is performed and samples are sent for histopathology or microbiology. When disseminated actinomyces is diagnosed, patients should be treated with antibiotics and most recover completely from their infection, as was the case with our patient. This case report clearly illustrates how the diagnosis can be delayed until after a surgical procedure due to clinical and radiographic findings concerning for a malignancy. Although this is a single case presentation, pelvic actinomyces has been demonstrated to mimic OC in prior reports.

Written informed consent was obtained from the patient for publication of this case report and accompanying images. This retrospective review of patient data did not require ethical approval in accordance with local/national guidelines.

K.E.H. has the following conflicts to report: Strata Oncology (partner former employee), Sanofi (research funding, completed), AbbVie (stockholder), Vistagen Therapeutics (stockholder), Illumina (stockholder), Halozyme (stockholder), Bristol Myers Squibb (stockholder), Gilead (stockholder). M.D. and O.D.L. declare no competing interests.

This study was not supported by any sponsor or funder.

M.D. and O.D.L. collected the patient data and contributed to the manuscript. M.D. was lead on the case report. K.E.H. supervised the data collection and manuscript production including reviewing and editing the manuscript.

Clinical information and pertinent images relevant to this case are included in this article. Further information is not publicly available due to HIPPA, but further inquiries can be directed to the corresponding author.