Peritoneal splenosis mimicking peritoneal metastases from invasive ductal carcinoma of the breast (IDC).

Clinical History

A 51-year-old female with newly diagnosed breast carcinoma with axillary nodal involvement underwent a staging contrast-enhanced CT (CECT) which reported nodularity in the peritoneal cavity. These were interpreted as possible peritoneal metastatic deposits. To characterise this further, the patient was subjected to ultrasound guided peritoneal nodule biopsy.

Imaging Findings

The patient was initially diagnosed with breast malignancy following triple assessment, including mammography and ultrasound.

Staging CECT TAP (thorax abdomen pelvis) was performed with intravenous contrast and the only suspicious findings apart from known breast malignancy, were peritoneal nodules. As there were no previous CECT examinations for comparison, the possibility of peritoneal metastatic disease was raised. The spleen was seen in a normal position and although it looked a little small and irregular, it looked otherwise normal.

Histological examination of biopsies taken from the left upper quadrant peritoneal nodules revealed fragmented cores of haemorrhagic lymphoid tissue with prominent vascularity, features which were considered to be in keeping with non-neoplastic splenic tissue.

Upon retrieving the patient's notes after MDT discussion, it was confirmed that decades previously, the patient had suffered splenic injury/laparotomy following trauma. It was therefore concluded following a review of the patient’s CECT and a literature review, that splenosis was the cause of the peritoneal nodularity.

Discussion

We present a case with peritoneal splenosis where initially a differential of metastasis was considered.
Literature review shows that incidence of peritoneal metastases is more frequent in ILC compared with IDC. Breast cancer metastases to the GI tract are rare occurences [1], however those with a lobular pathology have an increased tendency of metastasising in this pattern, including dissemination to the peritoneum. Although to a much lesser degree, peritoneal metastases have been confirmed in IDC of the breast [2]. Garcia-Fernandez et al[3] published a comparative long term study with 1600 IDC and 145 ILC patients and peritoneal spread was seen to be seven times higher for ILC (2.1%) compared with IDC (0.3%). A large study with over 3000 breast cancer patients by Bertozzi et al[4] reports 0.7% peritoneal metastases overall. Lobular histology was seen to be an independent risk factor for breast cancer peritoneal metastases. A case report of thoracic splenosis mimicking breast cancer metastases has been published. That patient presented several years following thoraco-abdominal trauma as reported by Gelsomino et al[5]. In another case report, a patient with remote history of splenic trauma was diagnosed with intra-abdominal splenosis using Tc-99m Sulpher Colloid SPECT imaging[6].
Our case demonstrates the importance of MDT review and awareness of this condition among clinicians and radiologists to potentially avoid a needle test whenever possible. If there are no other suspicious lesions on staging CT then we might consider doing red cell scintigraphy in the future for such cases.
No treatment is required for peritoneal splenosis.
This case describes peritoneal splenosis which was picked up on imaging in a patient recently diagnosed with IDC grade 3. The reporting radiologist was unaware of history of splenic trauma.
Although peritoneal metastases are rare in invasive ductal cancers, there are several reported cases and therefore this diagnosis should be considered when reporting staging scans for known IDC and ILC.
In patients with previous splenectomy or splenic trauma, splenosis should be considered as a possibility if there are peritoneal nodules on staging CECT for malignancy. Therefore a thorough review of past medical history is essential when encountering unexpected findings.
There are at least three potential ways to manage these findings – some use history and imaging findings alone, others use red cell scintigraphy. Other centres, like in this case use cytological / histopathological confirmation either through radiologically guided biopsy or laparoscopic / laparotomy approach.

Differential Diagnosis List

Final Diagnosis

Peritoneal splenosis

URL:	https://eurorad.org/case/15227
DOI:	10.1594/EURORAD/CASE.15227
ISSN:	1563-4086