Splenosis is the implantation of ectopic splenic tissue after splenic injury or splenectomy. Signs and symptoms of splenosis vary based on anatomic location; however, it remains asymptomatic in many cases. On radiographic imaging, splenosis often appears as a soft tissue mass and can be diagnosed using heat-damaged red blood cell scintigraphy, a non-invasive imaging modality. Radiographic findings of splenosis on imaging may be suspicious for metastatic disease in patients with known solid organ tumours. It is important to have a high degree of suspicion for splenosis with known history of splenic trauma or splenectomy in order to avoid invasive procedures and guide appropriate management.
- Breast cancer
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Splenosis is defined as the autotransplantation of splenic tissue and can occur months to many years after splenectomy or splenic trauma.1 Although splenosis most commonly occurs in the abdomen, it can occur anywhere in the body. Thoracic splenosis specifically is a rare phenomenon first described in 1937 that may occur when diaphragmatic rupture occurs in conjunction with splenic injury, resulting in splenic tissue in the thoracic cavity.2 In contrast with abdominal splenosis, which may cause abdominal pain, gastrointestinal bleeding or obstruction, thoracic splenosis is often asymptomatic.3 On radiographic imaging, splenosis can mimic malignancy or metastatic lesions4 and is therefore an important consideration in the care of oncology patients. Core needle biopsy, while considered the gold standard for definitive diagnosis, is an invasive procedure with potential for complications including haemorrhage from splenic tissue. The presence of ectopic splenic tissue can be also confirmed through a highly sensitive and specific technetium-99m-labelled denatured red blood cell scan.1 A high degree of clinical suspicion for splenosis is critical to avoid unnecessary procedures and ensure proper treatment for patients with solid tumours. In this report, we describe the case of a patient with newly diagnosed breast cancer and thoracic splenosis in the setting of prior trauma.
A woman in her 50s presented to our institution with stage III (T2N1M0) low ER/PR+ and HER2neu non-amplified invasive ductal carcinoma. Initial mammogram in 2018 showed two masses in the left breast and abnormal lymph nodes in the left axillary region that were biopsied to confirm the diagnosis. Subsequent staging CT scans showed lobular, pleural-based soft tissue masses throughout the left lung (figure 1) that were initially concerning for metastatic disease. On further elicitation of history, it was revealed that she had a history of motor vehicle trauma approximately 30 years ago leading to splenic injury and subsequently had a splenectomy. The patient also recalled a history of chest tube placement due to blood in her thoracic cavity and thus, likely had diaphragmatic trauma at this time. Given this history, thoracic splenosis was suspected. Positron emission tomography-computed tomography (PET-CT) scan showed mild to moderate Fluorodeoxyglucose (FDG) avidity in the pulmonary pleural soft tissue deposits (figure 2) as opposed to intense FDG avidity of the primary breast mass, suggesting the masses were more likely splenosis rather than metastatic disease. To confirm the diagnosis, heat-damaged tagged red blood cell scan was completed. The tagged red blood cell scan showed radiotracer uptake corresponding to several soft tissue lesions in the posterior and inferior pleura, but no uptake in the known tumour locations in breast and left axillary lymph nodes (figure 3), consistent with thoracic splenosis. Regarding treatment for her localised disease, this patient received standard of care curative intent neoadjuvant chemotherapy with near complete response to her breast cancer followed by bilateral mastectomy, postmastectomy radiation and adjuvant letrozole. She is currently on surveillance with no new evidence of disease recurrence.
In the case described above, the patient received CT scans of the chest, abdomen and pelvis to assess for metastasis once receiving the initial diagnosis of breast cancer. The chest CT showed soft tissue masses in the pleura which were read as ‘consistent with metastatic disease’; however, these were only mildly to moderately FDG avid on PET-CT. Based on the suspicion of possible splenosis and need to confirm the diagnosis, a heat-damaged red blood cell scintigraphy (Tc99m Prep UltraTag RBC 23.3 mCi IV, Rt AC, 20180518092700, LAH) was completed. This test uses technetium-99m-labelled denatured red blood cells to assess morphology of the spleen or detect ectopic splenic tissue in the case of splenectomy. In these cases, high levels of tracer uptake are noted in splenic tissue due to rapid sequestration of damaged red blood cells.5 Although less specific than the heat-damaged red blood cell scan, a sulfur colloid scan is another non-invasive modality used to identify splenic tissue >2 cm in size.6 In this study, technetium sulfur colloid (Tc-99m SC) is given intravenously and rapidly removed by the reticuloendothelial system of the spleen, liver and bone marrow.7 It can also be completed with single photon emission CT (SPECT) to improve sensitivity.6 In addition to sulfur colloid and heat-damaged red blood cell scans, biopsy of suspected splenosis can also be completed to confirm the diagnosis. However, this invasive procedure carries a risk of haemorrhage of splenic tissue.
In addition to splenosis, several other diagnoses were considered for this patient’s soft tissue masses on CT. The most concerning diagnosis was metastatic cancer, given known primary tumours in her left breast. To further assess for metastatic disease versus thoracic splenosis, heat-damaged red blood cell scintigraphy was completed. The study showed significant radiotracer uptake in the pleural soft tissue masses, but not the left breast or axillary lymph nodes, consistent with splenic tissue and not metastatic disease. Other differential diagnoses for splenosis include lymphoma, infection and localised fibrosis. However, given the history of known malignancy and splenic injury, these diagnoses were not heavily considered or worked up further.
The heat-damaged red blood cell scintigraphy confirmed that the pleural soft tissue mass seen on CT was ectopic splenic tissue. Splenosis itself does not require any medical or surgical intervention. While patients without splenic function need antibiotic prophylaxis to protect against infections caused by encapsulated organisms, splenosis provides some immune benefit and often does not require patients to be on antibiotic prophylaxis. One review found a 12.6-fold increase in developing septicaemia postsplenectomy, compared with only an 8.6-fold increase in septicaemia in post-traumatic splenectomy patients. The difference is thought to be due to benefits conferred by ectopic splenic tissue.8 Our patient was treated with guideline-directed therapy for her localised breast cancer with neoadjuvant chemotherapy (doxorubicin, cyclophosphamide, paclitaxel), bilateral mastectomy, and postmastectomy radiation and remains on adjuvant letrozole. She did not experience any uncommon side effects from chemotherapy or infections throughout her treatment course.
Outcome and follow-up
To date, this patient is on surveillance with no evidence of disease recurrence. Follow-up PET-CT scans continue to show mildly FDG avid, unchanged pleural soft tissue densities consistent with known thoracic splenosis. Imaging to date has shown no evidence of metastatic disease and stable postoperative changes. The patient continues to take letrozole with no adverse effects and follows regularly with medical oncology.
Previous research has identified 65 cases of thoracic splenosis in the literature between 1937 and 2002. In each case, the patient had a history of thoracoabdominal trauma and splenectomy, as well as thoracic splenosis located in the left hemithorax. Interestingly, the time from initial trauma to diagnosis of splenosis ranged from 3 to 45 years with an average of 21 years. Some cases were discovered on chest radiograph, but the low density of splenic tissue may contribute to splenosis only being well visualised on CT scans. About three-quarters of the patients studied here had multiple nodules on imaging compared with a single nodule, and while the majority of cases were asymptomatic, a small number of patients did report thoracic pain and haemoptysis.9 Since thoracic splenosis was first documented in the literature through a case series in 1937, there have been only four documented cases in cancer patients.10–13 In each of the four cases, all patients had a history of splenic injury secondary to trauma. A case report published in 2016 described thoracic splenosis in a patient with previously resected breast cancer. Evaluation for this patient’s adjuvant therapies showed para-cardiac and splenic masses in addition to pleural nodules on CT. Further questioning during diagnostic thoracoscopy work-up revealed a history of splenectomy after sustaining thoracoabdominal trauma approximately 30 years ago. The patient then underwent a heat-damaged red blood cell scan using technetium-99, similar to our patient, and SPECT which confirmed the diagnosis of thoracic and abdominal splenosis.10 A fifth case describes the incidental finding of thoracic splenosis in a patient who had history of breast cancer treated approximately 5 years ago with surgery and radiation.14
To our knowledge, this is only the third case report to describe thoracic splenosis in a patient with known breast cancer and the first to describe thoracic splenosis in a patient with a new diagnosis of breast cancer. In our case, the diagnosis of thoracic splenosis determined that our patient had local instead of metastatic disease and subsequently guided treatment. In addition to directing medical and surgical treatments, the diagnosis of splenosis helped rule out stage IV, metastatic disease and address the significant psychological distress accompanying a cancer diagnosis and implications of a ‘stage IV’ cancer.15 In oncology patients with history of splenic trauma or splenectomy and suspicious masses on imaging, clinicians should have a high index of suspicion for splenosis and can confirm the diagnosis through a non-invasive heat-damaged red blood cell scintigraphy. While splenosis itself does not require any intervention, it is important to identify splenic tissue on imaging in order to provide appropriate and high-quality care to patients.
Obtaining a detailed medical and surgical history in oncology patients is important to uncover history of splenic injury.
Clinicians should have a high index of suspicion for splenosis in oncology patients with imaging findings suspicious for malignancy and history of splenic injury.
Splenosis can be diagnosed with a non-invasive heat-damaged red blood cell scintigraphy.
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Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: KJ and MV. The following authors gave final approval of the manuscript: KJ and MV.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests Dr. Vasekar is the recipient of the Diversity in Clinical Trials- Winn CDA sponsored by BMS Foundation, 2022- 2024.
Provenance and peer review Not commissioned; externally peer reviewed.