CASE 18287 Published on 03.10.2023

Pelvic actinomycosis mimicking ovarian malignancy


Genital (female) imaging

Case Type

Clinical Cases


Rafaela Pereira, Mariana Roque

Serviço de Imagiologia Geral, Centro Hospitalar Universitário Lisboa Norte, CHULN – Hospital de Santa Maria, Lisboa, Portugal


26 years, female

Area of Interest Genital / Reproductive system female, Pelvis ; No Imaging Technique
Clinical History

A 26-year-old woman presented with pelvic and bilateral lumbar pain, associated with a 6-month history of weight loss and night sweats. Medical history was unremarkable, other than the removal of an intrauterine device 2 years earlier. Laboratory tests revealed a mild increase in inflammatory markers and acute kidney injury. Tumor markers were normal.

Imaging Findings

Suprapubic ultrasound (US) and computed tomography (CT) scan were initially performed and showed bilateral adnexal masses, predominantly solid, with indistinct margins and heterogenous enhancement (Figure 1). There was extension across tissue planes and involvement of adjacent organs.

Pelvic magnetic resonance imaging (MRI) (Figure 2) demonstrated pelvic masses with intermediate and heterogeneous T2 signal intensity, as well as multilocular cystic areas. The lesions had intermediate-low T1 signal intensity, heterogeneous enhancement of the solid components, and restricted diffusion. There was extensive inflammatory fat infiltration of the pelvis, mimicking invasive features of pelvic structures, namely the cervix and body of the uterus, the rectum, and the right pelvic wall.

There were no ascites, lymph node involvement, or peritoneal carcinomatosis.



Actinomycosis is a rare chronic granulomatous disease caused by an anaerobic gram-positive bacteria. Actinomyces is a frequent commensal in the oral cavity, vagina, and large bowel [1, 2].

Clinical Perspective

Clinical presentation may be very indolent and includes abdominal pain with or without palpable mass, weight loss, fever, abnormal vaginal discharge, bowel obstruction, or hydronephrosis [3, 4]. Laboratory tests usually show positive inflammation markers and anaemia [3].

Predisposing factors include intrauterine device (IUD), chronic inflammatory diseases, abdominal surgery, and penetrating trauma [2, 3]. Although IUD was removed 2 years earlier, we believe it was a predisposing factor in our case, considering that the disease has a subacute or chronic course, months or years before patient presentation.

Imaging Perspective

Although the US is usually the first-line imaging study, CT and/or MRI are essential for establishing the extent of the disease.

Pelvic actinomycosis usually presents as a complex gynaecological mass that does not respect anatomical barriers [2, 3]. This aggressive pattern of infiltration is due to the secretion of proteolytic enzymes and mimics locally advanced gynaecological malignancy [2, 3].

The masses are predominantly solid, as seen in our case, or mixed cystic and solid lesions, with indistinct margins, irregularly thickened walls, and inhomogeneous enhancement [4]. Small cystic components with enhancing rims and gas within the lesion may also be present and suggest abscedation [4].

At MRI, the solid components have intermediate signal intensity on T1-weighted images, intermediate-low signal intensity on T2, and heterogeneous enhancement [4]. Cystic components have mildly high signal intensity on T2 [4].

The contiguous spread of infection generates extensive inflammatory fat infiltration of the perirectal, pericolic, and/or perienteric spaces [3]. Regional lymphadenopathy and ascites are not common findings [3, 4].


Treatment consists of long-term antibiotic therapy [4]. Surgery or interventional procedures may be required to reduce the inflammatory process and to treat complications, such as bowel strictures and hydronephrosis [4].

In our case, a CT-guided core biopsy was performed. The specimen analysis revealed connective stroma with intense lymphoplasmacytic and neutrophilic inflammatory infiltration, as well as granulation tissue and Actinomyces colonies. There were no malignant cells.

Our patient was successfully treated with long-term antibiotic therapy.  Hydronephrosis and acute kidney failure progressively improved with conservative treatment. No surgery nor other invasive treatments were required.

Follow-up CT scan, 6 months after treatment, demonstrated noticeable regression of the previously described findings (Figure 3).

Take Home Messages

  • Pelvic actinomycosis is a rare chronic suppurative and granulomatous disease.
  • Clinical and radiological features can lead to misdiagnosis, as they mimic other inflammatory disorders and gynaecological malignancy.
  • The diagnosis is challenging and often requires microbiological and/or histopathological confirmation.


Written informed consent for publication has been obtained.

Differential Diagnosis List
Pelvic actinomycosis
Tuberculous pelvic inflammatory disease
Ovarian metastasis
Ovarian primary
Final Diagnosis
Pelvic actinomycosis
Case information
DOI: 10.35100/eurorad/case.18287
ISSN: 1563-4086