Intrapancreatic accessory spleen: findings on MR Imaging, CT, US and scintigraphy, and the pathologic analysis

Solid and cystic intrapancreatic accessory spleen: report of 10 cases in a single institution

BACKGROUND

Precise diagnosis of intrapancreatic accessory spleen (IPAS) remains challenging due to its rarity and diverse presentations. Despite comprehensive examinations, including radiography and other diagnostic methods, the potential for malignancy cannot be excluded, often leading to unnecessary pancreatic surgeries. We review our institutional experience to provide insights for accurately distinguishing IPAS.

METHODS

We retrospectively reviewed 10 patients who underwent distal pancreatectomy for the lesion in the pancreas tail which was determined to be IPAS on final pathology at our institution between January 2020 and April 2024. The presenting symptoms, medical history, preoperative imaging, operative therapy, final pathology and postoperative course were evaluated.

RESULTS

Patient ages ranged from 30 to 72 (median 55.5), including six women and four men. Most patients were asymptomatic. One patient had the medical history of splenectomy. Lesions ranged from 1.4 to 7.3 cm (mean 2.9 cm). All lesions were located in the pancreatic tail. On radiologic evaluation, these lesions had both solid and cystic presentations. The most common operative approach was laparoscopic distal pancreatectomy and splenectomy. Four patients were diagnosed with epidermoid cysts arising in intrapancreatic accessory spleen (ECIPAS) on final pathologic evaluation.

CONCLUSIONS

IPAS are predominantly benign lesions which have solid and cystic presentations commonly mistaken for pancreatic neoplasms. Combining CT, MRI, EUS-FNA and nuclear medicine may enhance IPAS detection, though no definitive diagnostic method exists. Increased awareness of IPAS in the differential diagnosis of pancreatic tail tumors, coupled with advancements in imaging techniques could improve diagnostic accuracy and exclude malignancy, preventing unnecessary surgeries.

Mimics of pancreatic neoplasms at cross-sectional imaging: Pearls for characterization and diagnostic work-up

Interpreting imaging examinations of the pancreas can be a challenge. Several different entities can mimic or mask pancreatic neoplasms, including normal anatomic variants, non-pancreatic lesions, and both acute and chronic pancreatitis. It is important to distinguish these entities from pancreatic neoplasms, as the management and prognosis of a pancreatic neoplasm, particularly adenocarcinoma, have considerable impact on patients. Normal pancreatic variants that mimic a focal lesion include focal fatty atrophy, annular pancreas, and ectopic pancreas. Extra-pancreatic lesions that can mimic a primary pancreatic neoplasm include vascular lesions, such as arteriovenous malformations and pseudoaneurysms, duodenal diverticula, and intra-pancreatic accessory spleen. Both acute and chronic pancreatitis can mimic or mask a pancreatic neoplasm and are also associated with pancreatic ductal adenocarcinoma. Awareness of these entities and their imaging features will enable the radiologist to narrow the differential diagnosis, provide recommendations that expedite diagnosis and avoid unnecessary work-up or delays in patient care.

Differentiation of intrapancreatic accessory spleen from pancreatic neuroendocrine tumor using MRI R2

PURPOSE

To evaluate the performance of R2* in distinguishing intrapancreatic accessory spleens (IPASs) from pancreatic neuroendocrine tumors (PNETs).

METHODS

Two radiologists (R1 and R2) retrospectively reviewed the MRIs of 20 IPAS and 20 PNET patients. IPASs were diagnosed with uptake on 99mTc labeled heat-damaged red blood cell scintigraphy or characteristic findings on CT/MRI and ≥ 12 month-long-stability. PNETs were histopathologically diagnosed with resection. Using McNemar test, sensitivities and specificities of the diagnostic criterion based on R2* mass-to-spleen ratio (MSR) were compared with those of the other criteria using contrast-enhanced (CE) MRI and apparent diffusion coefficient (ADC) MSR.

RESULTS

The study included 40 patients (median age, 54; interquartile range, 43-65; 24 men, 16 women). IPASs exhibited spleen-isointensity on T2WI, late arterial and portal phases, and diffusion-weighted images more frequently than PNETs (p <.05). ADC MSRs were lower (p <.001) and R2* MSRs were higher (p <.001) in IPASs compared to PNETs. For R1, sensitivity and specificity were 45.0% and 100.0% for criterion 1 (spleen-isointensity on CE-MRI); 45.0% and 85.0% for criterion 2 (ADC MSR ≤ 1.08); 90.0% and 95.0% for criterion 3 (0.9 ≤ R2* MSR ≤ 1.7). For R2, 75.0% and 100.0%; 45.0% and 90.0%; 90.0% and 100.0%. Criterion 3 showed higher sensitivity than criterion 1 for R1 (p =.004), and criterion 2 for R1 and R2 (p =.012). There was no difference in specificity.

CONCLUSION

For differentiating IPAS from PNET, R2* showed higher sensitivity than, and similar specificity to CE-MRI and ADC.

Imaging the pancreas with photon-counting CT - A review of normal pancreatic anatomy

PURPOSE

Compared to conventional energy integrating detector CT, Photon-Counting CT (PCCT) has the advantage of increased spatial resolution. The pancreas is a highly complex organ anatomically. The increased spatial resolution of PCCT challenges radiologists' knowledge of pancreatic anatomy. The purpose of this review was to review detailed macroscopic and microscopic anatomy of the pancreas in the context of current and future PCCT.

METHOD

This review is based on a literature review of all parts of pancreatic anatomy and a retrospective imaging review of PCCT scans from 20 consecutively included patients without pancreatic pathology (mean age 61.8 years, 11 female), scanned in the workup of pancreatic cancer with a contrast enhanced multiphase protocol. Two radiologists assessed the visibility of the main and accessory pancreatic ducts, side ducts, ampulla, major papilla, minor papilla, pancreatic arteries and veins, regional lymph nodes, coeliac ganglia, and coeliac plexus.

RESULTS

The macroscopic anatomy of the pancreas was consistently visualized with PCCT. Visualization of detailed anatomy of the ductal system (including side ducts), papillae, arteries, vein, lymph nodes, and innervation was possible in 90% or more of patients with moderate to good interreader agreement.

CONCLUSION

PCCT scans of the pancreas visualizes previously unseen or inconsistently seen small anatomical structures consistently. Increased knowledge of pancreatic anatomy could have importance in imaging of pancreatic cancer and other pancreatic diseases.

Spectrum of Heterotopic and Ectopic Splenic Conditions

A spectrum of heterotopic and ectopic splenic conditions may be encountered in clinical practice as incidental asymptomatic detection or symptomatic diagnosis. The radiologist needs to be aware of these conditions and their imaging characteristics to provide a prompt correct diagnosis and avoid misdiagnosis as neoplasm or lymphadenopathy. Having a strong knowledge base of the embryologic development of the spleen improves understanding of the pathophysiologic basis of these conditions. Spleen-specific imaging techniques-such as technetium 99m (99mTc)-labeled denatured erythrocyte scintigraphy, 99mTc-sulfur colloid liver-spleen scintigraphy, and MRI with ferumoxytol intravenous contrast material-can also be used to confirm the presence or absence of splenic tissue. Heterotopic splenic conditions include splenules and splenogonadal fusion (discontinuous or continuous forms). These heterotopic conditions are caused by incomplete fusion of the splenic primordia (splenule) and abnormal fusion of the gonadal and splenic tissue (splenogonadal fusion). Ectopic splenic conditions arise in patients with a prior splenic injury (splenosis), laxity or maldevelopment of the splenic ligaments (wandering spleen), or heterotaxy syndromes (polysplenia and asplenia). Importantly, these heterotopic and ectopic splenic conditions can also manifest with complications, including vascular torsion and rupture. ©RSNA, 2024.

Giant Cyst of Intrapancreatic Accessory Spleen Mimicking a Malignant Cystic Neoplasm of the Pancreas: A Case Report

INTRODUCTION

Epidermoid cyst in an intrapancreatic accessory spleen (ECIPAS) is an exceedingly rare pancreatic lesion that is always mistakenly suspected of malignancy preoperatively.

CASE SUMMARY

A 25-year-old male patient incidentally found a giant mass in the left upper abdomen neighboring the hilum of the spleen. The patient denied any obvious discomfort. Except for a slightly elevated carbohydrate antigen 19-9 (CA-19-9, 43.5 U/mL), no abnormal laboratory test results were found. Contrast-enhanced computed tomography, conventional ultrasound, and magnetic resonance imaging were performed. The patient received a laparoscopic distal pancreatectomy. The final pathology showed ECIPAS. The postoperative course was uneventful and no signs of recurrence during 2 years of follow-up.

DISCUSSION

For an incidental pancreatic cystic lesion, ECIPAS should be considered in the differential diagnosis. ECIPAS may mimic pancreatic cystadenoma. Imaging follow-up or surgical removal may be useful for the exclusion of malignant risks in ECIPAS.

Pictorial Review of Rare Pancreatic Tumors and Tumor-like Lesions: Radiologic-Pathologic Correlation

Rare pancreatic tumors and non-neoplastic tumor-like lesions present a diagnostic challenge due to their uncommon occurrence and overlapping imaging characteristics with more prevalent pancreatic neoplasms. Advances in imaging technologies and diagnostic criteria have contributed to increased detection of these rare entities in clinical practice. This pictorial review focuses on the radiologic-pathologic correlation of rare pancreatic tumors, including colloid carcinoma, acinar cell carcinoma, pancreatoblastoma, primary pancreatic lymphoma, and non-neoplastic tumor-like lesions such as hamartomas and inflammatory pseudotumors. Detailed imaging features, such as signal intensities on MRI and enhancement patterns on CT, are correlated with pathological findings to assist in the differential diagnosis. Familiarity with these characteristics is crucial for radiologists to ensure accurate diagnosis and guide appropriate treatment strategies, as management and prognosis significantly differ from common pancreatic neoplasms.

Imaging‑based diagnosis of intrapancreatic accessory spleen: A case report

During a routine ultrasound examination of the abdomen, a 60-year-old male patient was diagnosed with mass in the tail of the pancreas. However, computed tomography (CT) suggested that the lesion was an intrapancreatic accessory spleen (IPAS). IPAS is a congenital anomaly, which usually does not present with symptoms. IPAS occurs during embryologic splenic development when a portion of the splenic tissue fails to fuse with the main body of the spleen. IPAS does not require treatment, except when it is combined with idiopathic thrombocytopenic purpura. In the present case, the diagnosis of IPAS was confirmed using magnetic resonance imaging (MRI). On CT and MRI, the IPAS had a density and intensity comparable with that of the spleen in all plain and contrast-enhanced phases. Due to comorbidities, the patient refused further evaluation or surgery. The lesion was periodically monitored using CT every 1-2 years. Since the tumour was stable during the 7-year follow-up, it was concluded that it was an IPAS. In patients that cannot undergo surgery, a characteristic location (near the spleen) and imaging features (such as a 'zebra-patterned' enhancement in the arterial phase on CT and high signal intensity on diffusion-weighted imaging sequences on MRI, which is comparative to that of the normal spleen) may allow for a diagnose of IPAS with a high level of certainty. Being aware of this condition could aid a correct diagnosis of IPAS and prevent unnecessary surgery.

Laparoscopic excision of accessory spleen for recurrent autoimmune hemolytic anemia after splenectomy: a case report

BACKGROUND

Splenectomy is indicated in cases of autoimmune hemolytic anemia (AIHA), which are refractory to medical management. In post-splenectomy, there exists a theoretical risk of AIHA recurrence, especially if an accessory spleen undergoes compensatory hypertrophy. In this context, we present a unique case of recurrent AIHA managed through laparoscopic excision of the accessory spleen (LEAS).

CASE PRESENTATION

A 60-year-old male underwent laparoscopic splenectomy (LS) for AIHA refractory to standard medical therapies. Following the surgery, there was a marked improvement in hemolytic anemia symptoms, and oral steroid therapy was terminated 7 months post-LS. Nonetheless, a year after the LS, the patient exhibited a marked decline in hemoglobin levels, dropping to a concerning 5.8 g/dl, necessitating the reintroduction of oral steroids. A subsequent contrast-enhanced computed tomography (CT) scan unveiled an enlarged accessory spleen. The patient then underwent LEAS, during which the accessory spleen, obscured within adipose tissue, proved challenging to visualize laparoscopically. This obstacle was surmounted utilizing intraoperative ultrasonography (US), enabling successful excision of the accessory spleen. The post-surgical period progressed without complications, and the steroid dosage was reduced to one-twelfth of its initial preoperative quantity.

CONCLUSIONS

Recurrent AIHA can be instigated by post-splenectomy compensatory hypertrophy of the accessory spleen. Ensuring comprehensive splenic tissue excision is crucial in AIHA management to obviate recurrent stemming from hypertrophic remnants. In scenarios of AIHA recurrence tied to an enlarged accessory spleen, LEAS stands as a viable and effective therapeutic modality.

Laparoscopic Approach to Primary Splenic Cyst: Case Report and Review of the Literature

Splenic cysts are rare benign lesions of the spleen, often asymptomatic and incidentally discovered during imaging studies. While many splenic cysts remain asymptomatic and do not require intervention, surgical management becomes essential in cases of symptomatic cysts, large cysts, or when malignancy cannot be ruled out. Laparoscopic surgery has emerged as a minimally invasive and effective approach for treating splenic cysts, offering advantages such as shorter hospital stays, reduced postoperative pain, and faster recovery. In this case report, we describe our experience with laparoscopic surgery for a symptomatic splenic cyst in a young patient.

99mTc-Sn-colloid SPECT/CT in thoracic splenosis after esophageal cancer surgery

Splenosis occurs as a result of autotransplantation of splenic tissue following splenic injury or splenectomy. A 56-year-old man with esophageal cancer underwent thoracoscopic-assisted subtotal esophagectomy accompanied by three-field lymph node dissection, and retrosternal gastric tube reconstruction. The spleen was injured during the surgery and was removed. A retrosternal nodule of 12 mm in diameter was detected near the reconstructed gastric tube on computed tomography (CT) performed 3 years and 6 months postoperatively. Retrospectively, the nodule was observed in the same area on early postoperative CT and gradually increased in size. No accessory spleen was identified on the preoperative CT. Splenosis was suspected, and 99mTc-Sn-colloid single photon emission computed tomography (SPECT)/CT was performed. It revealed intense uptake in the retrosternal nodule, consistent with the diagnosis of thoracic splenosis. Subsequently, the patient has been under observation without treatment. 99mTc-labeled colloid SPECT/CT allowed confident diagnosis of thoracic splenosis following esophageal cancer surgery. This examination is considered valuable for the evaluation of ectopic splenic tissue.

Pancreatic Cancer and Its Mimics

Pancreatic ductal adenocarcinoma (PDAC) is the most common primary pancreatic malignancy, ranking fourth in cancer-related mortality in the United States. Typically, PDAC appears on images as a hypovascular mass with upstream pancreatic duct dilatation and abrupt duct cutoff, distal pancreatic atrophy, and vascular encasement, with metastatic involvement including lymphadenopathy. However, atypical manifestations that may limit detection of the underlying PDAC may also occur. Atypical PDAC features include findings related to associated conditions such as acute or chronic pancreatitis, a mass that is isointense to the parenchyma, multiplicity, diffuse tumor infiltration, associated calcifications, and cystic components. Several neoplastic and inflammatory conditions can mimic PDAC, such as paraduodenal "groove" pancreatitis, autoimmune pancreatitis, focal acute and chronic pancreatitis, neuroendocrine tumors, solid pseudopapillary neoplasms, metastases, and lymphoma. Differentiation of these conditions from PDAC can be challenging due to overlapping CT and MRI features; however, certain findings can help in differentiation. Diffusion-weighted MRI can be helpful but also can be nonspecific. Accurate diagnosis is pivotal for guiding therapeutic planning and potential outcomes in PDAC and avoiding biopsy or surgical treatment of some of these mimics. Biopsy may still be required for diagnosis in some cases. The authors describe the typical and atypical imaging findings of PDAC and features that may help to differentiate PDAC from its mimics. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Zins in this issue.

A review of contrast-enhanced ultrasound using SonoVue® and Sonazoid™ in non-hepatic organs

Contrast-enhanced ultrasound (CEUS) is a dependable modality for the diagnosis of various clinical conditions. A judicious selection of ultrasound contrast agent (UCA) is imperative for optimizing imaging and improving diagnosis. Approved UCAs for imaging the majority of organs include SonoVue, a pure blood agent, and Sonazoid, which exhibits an additional Kupffer phase. Despite the fact that the two UCAs are increasingly being employed, there is a lack of comparative reviews between the two agents in different organs diseases. This review represents the first attempt to compare the two UCAs in non-hepatic organs, primarily including breast, thyroid, pancreas, and spleen diseases. Through comparative analysis, this review provides a comprehensive and objective evaluation of the performance characteristics of SonoVue and Sonazoid, with the aim of offering valuable guidance for the clinical application of CEUS. Overall, further clinical evidences are required to compare and contrast the dissimilarities between the two UCAs in non-hepatic organs, enabling clinicians to make an appropriate selection based on actual clinical applications.

Diagnostic Endoscopic Ultrasound in Pancreatology: Focus on Normal Variants and Pancreatic Masses

Background

Endoscopic ultrasound (EUS) is a main tool in gastroenterology for both diagnosis and exclusion of pancreatic pathology. It allows minimally invasive assessment of various diseases or anatomic variations affecting the pancreas also with the help of new Doppler technologies, elastography, contrast-enhanced imaging including post hoc image processing with quantification analyses, three-dimensional reconstruction, and artificial intelligence. EUS also allows interventional direct access to the pancreatic parenchyma and the retroperitoneal space, to the pancreatic duct, pancreatic masses, cysts, and vascular structures.

Summary

This review aimed to summarize new developments of EUS in the field of pancreatology. We highlight the role of EUS in evaluating pancreatic pathology by describing normal anatomic variants like pancreas divisum, pancreatic lipomatosis, pancreatic fibrosis in the elderly and characterizing pancreatic masses, both in the context of chronic pancreatitis and within healthy pancreatic parenchyma. EUS is considered the optimal imaging modality for pancreatic masses of uncertain dignity and allows both cytological diagnosis and histology, which is essential not only for neoplastic conditions but also for tailoring therapy for benign inflammatory conditions.

Key Messages

EUS plays an indispensable role in pancreatology and the development of new diagnostic and interventional approaches to the retroperitoneal space and the pancreas exponentially increased over the last years. The development of computer-aided diagnosis and artificial intelligence algorithms hold the potential to overcome the obstacles associated with interobserver variability and will most likely support decision-making in the management of pancreatic disease.

Rare Solid Pancreatic Lesions on Cross-Sectional Imaging

Several solid lesions can be found within the pancreas mainly arising from the exocrine and endocrine pancreatic tissue. Among all pancreatic malignancies, the most common subtype is pancreatic ductal adenocarcinoma (PDAC), to a point that pancreatic cancer and PDAC are used interchangeably. But, in addition to PDAC, and to the other most common and well-known solid lesions, either related to benign conditions, such as pancreatitis, or not so benign, such as pancreatic neuroendocrine neoplasms (pNENs), there are solid pancreatic lesions considered rare due to their low incidence. These lesions may originate from a cell line with a differentiation other than exocrine/endocrine, such as from the nerve sheath as for pancreatic schwannoma or from mesenchymal cells as for solitary fibrous tumour. These rare solid pancreatic lesions may show a behaviour that ranges in a benign to highly aggressive malignant spectrum. This review includes cases of an intrapancreatic accessory spleen, pancreatic tuberculosis, solid serous cystadenoma, solid pseudopapillary tumour, pancreatic schwannoma, purely intraductal neuroendocrine tumour, pancreatic fibrous solitary tumour, acinar cell carcinoma, undifferentiated carcinoma with osteoclastic-like giant cells, adenosquamous carcinoma, colloid carcinoma of the pancreas, primary leiomyosarcoma of the pancreas, primary and secondary pancreatic lymphoma and metastases within the pancreas. Therefore, it is important to determine the correct diagnosis to ensure optimal patient management. Because of their rarity, their existence is less well known and, when depicted, in most cases incidentally, the correct diagnosis remains challenging. However, there are some typical imaging features present on cross-sectional imaging modalities that, taken into account with the clinical and biological context, contribute substantially to achieve the correct diagnosis.

Diagnostic accuracy of apparent diffusion coefficient to differentiate intrapancreatic accessory spleen from pancreatic neuroendocrine tumors

BACKGROUND

Intrapancreatic accessory spleen (IPAS) shares similar imaging findings with hypervascular pancreatic neuroendocrine tumors (PNETs), which may lead to unnecessary surgery.

AIM

To investigate and compare the diagnostic performance of absolute apparent diffusion coefficient (ADC) and normalized ADC (lesion-to-spleen ADC ratios) in the differential diagnosis of IPAS from PNETs.

METHODS

A retrospective study consisting of 29 patients (16 PNET patients vs 13 IPAS patients) who underwent preoperative contrast-enhanced magnetic resonance imaging together with diffusion-weighted imaging/ADC maps between January 2017 and July 2020 was performed. Two independent reviewers measured ADC on all lesions and spleens, and normalized ADC was calculated for further analysis. The receiver operating characteristics analysis was carried out for evaluating the diagnostic performance of both absolute ADC and normalized ADC values in the differential diagnosis between IPAS and PNETs by clarifying sensitivity, specificity, and accuracy. Inter-reader reliability for the two methods was evaluated.

RESULTS

IPAS had a significantly lower absolute ADC (0.931 ± 0.773 × 10^-3 mm²/s vs 1.254 ± 0.219 × 10^-3 mm²/s) and normalized ADC value (1.154 ± 0.167 vs 1.591 ± 0.364) compared to PNET. A cutoff value of 1.046 × 10^-3 mm²/s for absolute ADC was associated with 81.25% sensitivity, 100% specificity, and 89.66% accuracy with an area under the curve of 0.94 (95% confidence interval: 0.8536-1.000) for the differential diagnosis of IPAS from PNET. Similarly, a cutoff value of 1.342 for normalized ADC was associated with 81.25% sensitivity, 92.31% specificity, and 86.21% accuracy with an area under the curve of 0.91 (95% confidence interval: 0.8080-1.000) for the differential diagnosis of IPAS from PNET. Both methods showed excellent inter-reader reliability with intraclass correlation coefficients for absolute ADC and ADC ratio being 0.968 and 0.976, respectively.

CONCLUSION

Both absolute ADC and normalized ADC values can facilitate the differentiation between IPAS and PNET.

Accessory Spleen Mimicking an Intrahepatic Neoplasm: A Rare Case Report

Accessory spleen and splenosis are two types of ectopic spleen. An accessory spleen can be found in various sites in the abdomen, but an intrahepatic accessory spleen is very rare though many case reports of intrahepatic splenosis are available. This case report presents the incidental diagnosis of accessory spleen in the liver of a 57-year-old male while undergoing laparoscopic diaphragmatic repair. The patient had a history of splenectomy 27 years ago for hereditary spherocytosis, but his routine haemogram did not show any features of the ectopic splenic function. Intraoperatively, a mass was suspected in the liver and was resected. Histopathology revealed an accessory spleen with well-preserved red and white pulp architecture. Though a history of splenectomy suggested a diagnosis of splenosis, a well-encapsulated and preserved splenic architecture confirmed the diagnosis of accessory spleen. Accessory spleen or splenosis can be diagnosed radiologically using Tc-99m-labeled heat-denatured red blood cells (HRBC) and Tc-99m sulfur colloid scans, but the gold standard is histopathological examination. Ectopic spleen is mostly asymptomatic but usually results in unnecessary surgeries as it is difficult to differentiate from benign or malignant tumors. Thus, a high degree of suspicion and awareness is necessary for early and prompt diagnosis.

The Role of MRI in the Diagnosis of Solid Pseudopapillary Neoplasm of the Pancreas and Its Mimickers: A Case-Based Review with Emphasis on Differential Diagnosis

Solid pseudopapillary neoplasm (SPN) is rare pancreatic tumor occurring most commonly in young females. The typical imaging appearance of SPN is of well-defined, encapsulated, and large heterogeneous tumors, consisting of solid and cystic components due to various degrees of intralesional hemorrhage and necrosis. However, atypical imaging presentation in the form of small solid tumors or uniformly cystic lesions might also be seen, which can be explained by specific pathological characteristics. Other imaging features such as a round shape, the absence of main pancreatic duct dilatation, and slow growth, in combination with vague symptoms, favor the diagnosis of SPNs. Nevertheless, the radiological findings of SPN might overlap with other solid and cystic pancreatic neoplasms, such as neuroendocrine tumors, serous and mucinous neoplasms, and even small pancreatic adenocarcinomas. In addition, a few benign non-tumorous conditions including walled-of-necrosis, and intrapancreatic accessory spleen may also pose diagnostic dilemmas simulating SPNs on imaging studies. The aim of this manuscript is to provide a comprehensive overview of the typical and atypical imaging features of SPNs and to describe useful tips for differential diagnosis with its potential mimickers.

Various congenital anomalies and anatomical variations of the spleen: a multimodality pictorial review

There are various congenital anomalies and anatomical variations of the spleen (CAAVS). CAAVS are common and are often associated with systemic anomalies. Widespread use of computed tomography and magnetic resonance imaging in a variety of clinical situations has increased the detection of CAAVS. However, CAAVS are frequently overlooked and are occasionally misdiagnosed as pathologic disease entities. This article aimed to review the various manifestations of CAAVS with radiologic findings.

Ectopic lesions in the abdomen and pelvis: a multimodality pictorial review

Various ectopic lesions occur in the abdomen and pelvis and affect multiple organs including liver, gallbladder, pancreas, spleen, and organs of the genitourinary system. Ectopic organs may be present outside their normal positions, or ectopic tissues may develop while the original organ exists in its normal position. Both benign and malignant lesions can occur in ectopic organs and tissues. Owing to their unusual location, they can often be misdiagnosed as other lesions or even malignant lesions, such as metastasis or seeding. This multimodality pictorial review provides various cases of ectopic lesions in the abdomen and pelvis, which will help narrow the differential diagnosis and guide clinical decision-making.

Accessory Spleen Masquerading as an Intrapancreatic Tumor: A Case Report

The finding of splenic tissue within the pancreas, also known as splenosis or intrapancreatic accessory spleen (IPAS), is a relatively uncommon condition that presents as an intrapancreatic mass. The discovery of an intrapancreatic mass often prompts a thorough diagnostic workup for a primary pancreatic malignancy, often exposing patients to unnecessary risks associated with invasive testing and even surgery. The benign, asymptomatic nature of this finding places emphasis on utilizing non-invasive techniques for confirmation of the diagnosis, reducing risks of morbidity and mortality in this patient population. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) will display near-identical signal intensities (SI) between the spleen and the intrapancreatic mass, as well as identical contrast-enhancement patterns. Nuclear medicine evaluation with Tc-99m heat-damaged red blood cells (HDRBCs) is often used as a confirmatory test and allows for differentiation from malignancies.

Abdominal and pelvic splenosis: atypical findings, pitfalls, and mimics

Splenosis is an acquired form of ectopic splenic tissue that typically arises after trauma or splenectomy. It is often an incidental image finding in an otherwise asymptomatic patient, but the spectrum of symptoms varies based on the site of implantation. Radiologists should be familiar with the imaging features of splenosis to avoid mistaking it for malignancy. Splenosis has identical imaging features to that of the native spleen on US, CT, MRI, and nuclear medicine examinations. Therefore, when the radiologic findings support the diagnosis of splenosis, the patient can be spared invasive procedures for tissue sampling.

Cavernous hemangioma of an intrapancreatic accessory spleen mimicking a pancreatic tumor: A case report

BACKGROUND

Intrapancreatic accessory spleen (IPAS) is an uncommon condition, with the majority of cases presenting as solid lesions. Thus, this condition is frequently misdiagnosed as pancreatic solid neoplasm. Moreover, splenic cavernous hemangioma is a rare disorder, whereas lesions with a cystic appearance arising from IPAS have not been reported.

CASE SUMMARY

Herein, we present a case involving a 32-year-old male who had a complex cystic lesion in the tail of the pancreas revealed by conventional ultrasound. The lesion was misdiagnosed as a pancreatic cystadenoma because of its confusing anatomic location, as well as due to its peripheral nodular and internal septal enhancement patterns on contrast-enhanced ultrasound. After multidisciplinary discussion, the patient finally underwent laparoscopic pancreatic body and tail resections. Postoperative pathology demonstrated the lesion to be a cavernous hemangioma arising from the IPAS.

CONCLUSION

Cavernous hemangioma in the intrapancreatic accessory spleen may mimic pancreatic cystadenoma, which is a condition with the potential to be malignant. Imaging follow-ups or surgical interventions may be helpful for the exclusion of malignant risks in complicated cystic lesions, especially those with parietal and septal enhancements.

Intrapancreatic accessory spleen with an epidermoid cyst: a malignant mimicry

With the liberal use of CT scan for clinical diagnosis, clinicians are faced with an increasing number of pancreatic incidentalomas. Compared with other incidentalomas, pancreatic incidentalomas have higher chances of future malignant transformation. There are many differential diagnoses, and epidermoid cyst in an intrapancreatic accessory spleen (ECIPAS) is extremely rare, with only a handful of reports. Preoperative diagnosis is often complicated, and the final diagnosis is usually only made after surgical resection.We report a 34-year-old man who had an incidentally noted 2.8 cm pancreatic tail cystic lesion on a CT scan done for urinary symptoms. The lesion had a solid nodular component that was worrisome for malignancy, and the patient underwent further evaluation with an MRI scan and endoscopic ultrasound of the pancreas. The differential diagnoses of cystic degeneration of neuroendocrine tumour, branch-duct intraductal papillary mucinous neoplasm with worrisome features or ectopic intrapancreatic spleen were made. A multidisciplinary tumour board recommended surgical resection given risk features of malignancy. The patient subsequently underwent a laparoscopic distal pancreatectomy with splenectomy, and histology confirmed the diagnosis of ECIPAS.Imaging characteristics of ECIPAS are non-specific, and most patients have a diagnosis made only after surgery. Therefore, more evidence is warranted for accurate preoperative imaging diagnosis to avoid unnecessary pancreatic surgery, which is not without its risks.

Pancreatic Masses in Children and Young Adults: Multimodality Review with Pathologic Correlation

Masses and masslike lesions of the pancreas are uncommon in the pediatric population. However, owing to overlapping clinical and imaging features, it can be challenging to differentiate the various causes of pediatric pancreatic masses at initial patient presentation. Clinical data such as patient age, signs and symptoms at presentation, laboratory test results, and potential underlying cancer predisposition syndrome can be helpful when formulating a differential diagnosis. US may be the first imaging study to depict a pancreatic mass in a child, as this examination is frequently performed in children with nonspecific abdominal signs and symptoms because of its wide availability and relatively low cost and the lack of a need for sedation or anesthesia. CT or MRI is typically required for more thorough characterization of the mass and surgical planning. Complete characterization of pancreatic masses includes assessment of vascular involvement, local invasion, and extrapancreatic spread of tumor. The authors provide an up-to-date comprehensive review of the clinical manifestations, histopathologic features, and imaging findings of primary and secondary tumors of the pancreas in children and young adults. Advances in imaging, current prognostic information, and treatment paradigms also are highlighted. Finally, nontumorous masslike lesions of the pediatric pancreas, including vascular malformations, cystic disorders (eg, von Hippel-Lindau syndrome, cystic fibrosis), intrapancreatic accessory spleen, and autoimmune pancreatitis, are discussed. Online supplemental material is available for this article. ^©RSNA, 2021.

Acute Abdominal Pain due to Accessory Splenic Infarction in an Adult: A Case Report

Accessory spleens are common congenital anatomic variations that are usually asymptomatic. On the other hand, they can be clinically significant if complicated by hemorrhage, torsion, or infarction. This paper describes a case of an infarcted accessory spleen in a 30-year-old male who presented with abdominal pain. Abdominal CT and MRI revealed an isolated mass, 4.5 cm in size, in the perisplenic area. An infarcted accessory spleen was suspected. The patient underwent laparoscopic accessory splenectomy. Histopathology identified the mass as splenic tissue that had undergone ischemic necrosis. A definitive diagnosis of an infarcted accessory spleen was made, and the patient was discharged on day 5 after surgery symptom-free.

Recommendations for the Management of Incidental Pancreatic Findings in Adults by the Canadian Association of Radiologists Incidental Findings Working Group

The Canadian Association of Radiologists Incidental Findings Working Group consists of both academic subspecialty and general radiologists and is tasked with adapting and expanding upon the American College of Radiology incidental findings white papers to more closely apply to Canadian practice patterns, particularly more comprehensively dealing with the role of ultrasound and pursuing more cost-effective approaches to the workup of incidental findings without compromising patient care. Presented here are the 2021 Canadian guidelines for the management of pancreatic incidental findings. Topics covered include anatomic variants, fatty atrophy, pancreatic calcifications, ductal ectasia, and management of incidental pancreatic cysts.

Ferumoxytol-enhanced MR imaging for differentiating intrapancreatic splenules from other tumors

Objectives

Ferumoxytol is an ultra-small superparamagnetic iron oxide (USPIO) agent that is taken up by splenic tissue. This study describes our initial institutional experience of ferumoxytol-enhanced MRI (feMRI) for differentiating intrapancreatic splenules (IPS) from other pancreatic lesions.

Methods

In this retrospective study, patients with computed tomographic imaging that identified small enhancing lesions in the tail of the pancreas subsequently underwent feMRI for further characterization. The feMRI protocol included T2-weighted (T2w) imaging with and without fat suppression (FS), R2* mapping, diffusion-weighted imaging (DWI), and T1-weighted (T1w) imaging with FS, prior to contrast injection. Immediately after slow intravenous infusion with 3 mg/kg body weight ferumoxytol, T1w was repeated. Delayed imaging with all sequences were obtained 24–72 h after ferumoxytol administration.

Results

Seven patients underwent feMRI. In two patients, the pancreatic lesions were presumed as pancreatic neuroendocrine tumor (PNET) from feMRI and in the remaining 5 IPS. One of the two patients with PNET was symptomatic for NET. In another symptomatic patient with pathologically proven duodenal NET and suspected PNET, the pancreatic lesion was proven to be an IPS on feMRI. IPS demonstrated strong negative enhancement in feMRI on T2w and increased R2* values consistent with splenic tissue, while the presumed PNETs did not enhance. T2w FS was helpful on the pre-contrast images to identify IPS, while R2* did on post-contrast images. Neither DWI nor T1w contributed to differentiating PNETs from IPS.

Conclusions

This study demonstrates the potential utility of feMRI as a helpful adjunct diagnostic tool for differentiating IPS from other pancreatic lesions. Further studies in larger patient cohorts are needed.

Impact of PET data driven respiratory motion correction and BSREM reconstruction of 68Ga-DOTATATE PET/CT for differentiating neuroendocrine tumors (NET) and intrapancreatic accessory spleens (IPAS)

To evaluate whether quantitative PET parameters of motion-corrected ⁶⁸Ga-DOTATATE PET/CT can differentiate between intrapancreatic accessory spleens (IPAS) and pancreatic neuroendocrine tumor (pNET). A total of 498 consecutive patients with neuroendocrine tumors (NET) who underwent ⁶⁸Ga-DOTATATE PET/CT between March 2017 and July 2019 were retrospectively analyzed. Subjects with accessory spleens (n = 43, thereof 7 IPAS) and pNET (n = 9) were included, resulting in a total of 45 scans. PET images were reconstructed using ordered-subsets expectation maximization (OSEM) and a fully convergent iterative image reconstruction algorithm with β-values of 1000 (BSREM₁₀₀₀). A data-driven gating (DDG) technique (MOTIONFREE, GE Healthcare) was applied to extract respiratory triggers and use them for PET motion correction within both reconstructions. PET parameters among different samples were compared using non-parametric tests. Receiver operating characteristics (ROC) analyzed the ability of PET parameters to differentiate IPAS and pNETs. SUVmax was able to distinguish pNET from accessory spleens and IPAs in BSREM₁₀₀₀ reconstructions (p < 0.05). This result was more reliable using DDG-based motion correction (p < 0.003) and was achieved in both OSEM and BSREM₁₀₀₀ reconstructions. For differentiating accessory spleens and pNETs with specificity 100%, the ROC analysis yielded an AUC of 0.742 (sensitivity 56%)/0.765 (sensitivity 56%)/0.846 (sensitivity 62%)/0.840 (sensitivity 63%) for SUVmax 36.7/41.9/36.9/41.7 in OSEM/BSREM₁₀₀₀/OSEM + DDG/BSREM₁₀₀₀ + DDG, respectively. BSREM₁₀₀₀ + DDG can accurately differentiate pNET from accessory spleen. Both BSREM₁₀₀₀ and DDG lead to a significant SUV increase compared to OSEM and non-motion-corrected data.

Accessory sple­en in a dog: Macroscopic and microscopic findings

Accessory spleens are one or more areas of normal ectopic splenic tissue of variable size supplied by the branches of the splenic artery. A 7 year-old mixed breed male dog was fixed for use as a model in anatomy hall. During the abdominal dissection, the gross examination showed a 6.3×3.1×1 cm mass that was situated on the caudodorsal border of the spleen. Its appearance and firm consistency were similar to those of spleen. There was no connection between the spleen and this mass. It was supplied by accessory splenic artery. Microscopic examination of the mass revealed some structures similar to spleen.

Intrapancreatic Accessory Spleen Masquerading as a Pancreatic Mucinous Neoplasm

Incidentally discovered pancreatic cysts have become more common with increasing use of abdominal cross-sectional imaging. Tools that help us to better risk stratify a pancreatic cyst include advanced imaging techniques, such as pancreatic protocol computed tomography (CT) scan or magnetic resonance imaging (MRI) with cholangiopancreatography. Endoscopic ultrasound (EUS) and fine-needle aspiration (FNA) are invasive measures to better define and sample cysts especially if high-risk features are present. EUS may also yield pancreatic cyst fluid for analysis of carcinoembryonic antigen (CEA) which is elevated in mucinous cysts. This case highlights a rare finding of a mucinous, epidermoid cyst in an intrapancreatic accessory spleen (IPAS) with high-risk features on EUS.

Pitfalls in the MDCT of pancreatic cancer: strategies for minimizing errors

Multidetector computed tomography (MDCT) is a widely used cross-sectional imaging modality for initial evaluation of patients with suspected pancreatic ductal adenocarcinoma (PDAC). However, diagnosis of PDAC can be challenging due to numerous pitfalls associated with image acquisition and interpretation, including technical factors, imaging features, and cognitive errors. Accurate diagnosis requires familiarity with these pitfalls, as these can be minimized using systematic strategies. Suboptimal acquisition protocols and other technical errors such as motion artifacts and incomplete anatomical coverage increase the risk of misdiagnosis. Interpretation of images can be challenging due to intrinsic tumor features (including small and isoenhancing masses, exophytic masses, subtle pancreatic duct irregularities, and diffuse tumor infiltration), presence of coexisting pathology (including chronic pancreatitis and intraductal papillary mucinous neoplasm), mimickers of PDAC (including focal fatty infiltration and focal pancreatitis), distracting findings, and satisfaction of search. Awareness of pitfalls associated with the diagnosis of PDAC along with the strategies to avoid them will help radiologists to minimize technical and interpretation errors. Cognizance and mitigation of these errors can lead to earlier PDAC diagnosis and ultimately improve patient prognosis.

Spleen Scan for 68Ga-DOTATOC PET-Positive Pancreatic Tail Lesion: Differential Diagnosis of Neuroendocrine Tumor from Accessory Spleen

⁶⁸Ga-DOTATOC PET/CT is widely used as a functional imaging technique in the detection and characterization of neuroendocrine tumors (NETs). Pancreatic NET and intrapancreatic accessory spleen (IPAS) have similar radiologic characteristics in anatomical imaging and usually show high uptake of ⁶⁸Ga-DOTATOC. Thus, it is challenging to make a differential diagnosis between NET and IPAS when the tumor-like lesion is located in the pancreatic tail. Here, we present a case of ⁶⁸Ga-DOTATOC PET-positive pancreatic tail lesion with high arterial enhancement on CT and MRI. Since ^99mTc-labeled damaged red blood cell does not accumulate on NET, a negative spleen scan finding was a crucial diagnostic step to decide surgical resection, which was histologically proven as insulinoma. Our case shows a promising role of additional use of spleen scan with SPECT/CT for the differential diagnosis of ⁶⁸Ga-DOTATOC PET-positive pancreatic NET from the accessory spleen.

Laparoscopic spleen-preserving pancreatic resection for intrapancreatic accessory spleen: Case report

INTRODUCTION

Intrapancreatic accessory spleen (IPAS) has been rarely noted radiologically because the spatial resolution of conventional images was low. The infrequent presence of the accessory spleen in the pancreatic tissue could lead to inappropriate diagnosis, thereby necessitating a therapeutic approach. The present study reported such cases and summarized the available imaging findings to reduce unnecessary invasive surgeries.

PATIENT CONCERNS

The patient's complaint was "a pancreatic mass was found for half a month."

DIAGNOSIS

IPAS was eventually diagnosed by pathology.

INTERVENTIONS

Laparoscopic spleen-preserving pancreatic resection.

OUTCOMES

Postoperative course was uneventful and the patient was discharged from our hospital after 10 days.

CONCLUSIONS

When an asymptomatic pancreatic mass is detected, the diagnosis of IPAS should not be excluded, especially if the lesion has the same imaging features as the spleen. As a definite diagnosis of IPAS is difficult by a single examination, multiple techniques might be essential.

Intrapancreatic accessory spleen false positive to 68Ga-Dotatoc: case report and literature review

Background

Intrapancreatic accessory spleen (IPAS) is an uncommon finding of pancreatic mass. Differential diagnosis with pancreatic tumor, especially with non-functional neuroendocrine tumor (NF-NET), may be very hard and sometimes it entails unnecessary surgery. A combination of CT scan, MRI, and nuclear medicine can confirm the diagnosis of IPAS. 68-Ga-Dotatoc PET/CT is the gold standard in NET diagnosis and it can allow to distinguish between IPAS and NET.

Case presentation

A 69-year-old man was admitted to our hospital for an incidental nodule in the tail of the pancreas with focal uptake of 68-Ga-dotatate at PET/CT. NET was suspected and open distal splenopancreatectomy was performed. Pathologic examination revealed an IPAS.

Conclusion

This is the second IPAS case in which a positive 68Ga-Dotatoc uptake led to a false diagnosis of pancreatic NET. Here is a proposal of a literature review.

Various Congenital Abnormalities and Anatomic Variants of the Pancreas: A Pictorial Review

Numerous and various congenital abnormalities and anatomic variants of the pancreas (CAAVPs) have been reported. Some of them are not so uncommon. Recent advances and accessibility of various multiplanar imaging modalities today offer the increased capabilities of detection and full diagnosis of these CAAVPs. With a precise diagnosis, the symptomatic CAAVPs can not only be more specifically treated but even more their detection and exact description can modify the surgical or interventional strategy to avoid unexpected post-operative complications. This article aimed to review the embryogenesis of the pancreas and describe imaging findings of CAAVPs.

Laparoscopic intrapancreatic accessory splenectomy: A case report of recurrent immune thrombocytopenia in a 33 years old male patient after 6 years of splenectomy

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Intrapancreatic Accessory Spleen (IPAS) is a rare embryological benign abnormality.

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(IPAS) should be considered in patients with recurrent immune thrombocytopenia (ITP).

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Although IPAS is a challenging diagnosis, it can be detected by the recent advancement of medical imaging.

Introduction

Intra-pancreatic Accessory Spleen (IPAS) is a rare benign abnormality of splenic embryology that should be considered in any patient with recurrence of immune thrombocytopenia (ITP). The case demonstrates that remission could be achieved if an IPAS is correctly identified and safely removed.

Case presentation

We report a 33-years-old male patient who presented with chronic ITP relapsed 3 years post initial splenectomy. The patient presented with severe thrombocytopenia requiring steroids and intravenous immunoglobulin (IVIG).

Discussion

IPAS can be identified using enhanced CT scan along with Tc-99 m sulfur colloid scintigraphy. Our patient underwent CT scan of abdomen and pelvis and was found to have an IPAS originating from the tail of the pancreas which was subsequently removed laparoscopically. The patient was then tapered off steroids and was followed up regularly and found to have acceptable platelet levels and no symptoms for 30 months post-surgery.

Conclusion

The diagnosis of IPAS can be non-invasively made by an experienced radiologist with the recent advancement of medical imaging. Recognizing IPAS as a possible cause of ITP recurrence, and using minimally invasive approach can be performed safely and lead satisfactory outcomes.

Differentiation of intrapancreatic accessory spleen from small hypervascular neuroendocrine tumor of the pancreas: textural analysis on contrast-enhanced computed tomography

BACKGROUND

Intrapancreatic accessory spleens (IPASs) are usually misdiagnosed as pancreatic neuroendocrine tumors (PNETs). Texture analysis is valuable in tumor detection, diagnosis, and staging.

PURPOSE

To identify the potential of texture features in differentiating IPASs from small hypervascular PNETs.

MATERIAL AND METHODS

Twenty-one patients with PNETs and 13 individuals with IPASs who underwent pretreatment dynamic contrast-enhanced computed tomography (CT) were retrospectively analyzed. The routine imaging features-such as location, size, margin, cystic or solid appearance, enhancement degree and pattern, and lymph node enlargement-were recorded. Texture features, such as entropy, skewness, kurtosis, and uniformity, on contrast-enhanced images were analyzed. Receiver operating characteristic (ROC) analysis was performed to differentiate IPASs from PNETs.

RESULTS

No significant differences were observed in margin, enhancement degree (arterial and portal phase), lymph node enlargement, or size between PNETs and IPASs (all P > 0.05). However, IPASs usually showed heterogeneous enhancement at the arterial phase and the same degree of enhancement as the spleen at the portal phase, both of which were greater than those of PNETs (69% vs. 35%, P = 0.06; 100% vs. 29%, P = 0.04). Entropy and uniformity were significantly different between IPASs and PNETs at moderate (1.5) and high sigma values (2.5) (both P < 0.01). ROC analysis showed that uniformity at moderate and high sigma had the highest area under the curve (0.82 and 0.89) with better sensitivity (85.0-95.0%) and acceptable specificity (75.0-83.3%) for differentiating IPASs from PNETs.

CONCLUSIONS

Texture parameters have potential in differentiating IPASs from PNETs.

Epidermoid cyst in intrapancreatic accessory spleen: A systematic review

BACKGROUND/OBJECTIVES

Due to its rarity, epidermoid cyst in intrapancreatic accessory spleen (ECIPAS) is still a diagnostic dilemma during clinical practice. The aim of this review was to summarize the epidemiologic features and management of ECIPAS.

METHODS

MEDLINE and EMBASE were searched for English articles reporting on ECIPAS up to April 30th, 2018 following the methodology suggested by the PRISMA guidelines. Categorical variables were reported as frequency and percentage. Continuous variables were reported as median (range).

RESULTS

A total of 56 patients from 47 full articles were included for the final data synthesis. More than half of the ECIPASs (59%) were found incidentally. The female/male ratio was 1.33. ECIPAS is typically a single mono-/multi-lobular cystic lesions in the pancreatic tail with thickened cystic wall or various amount of solid component which had identical density/signal to the spleen on imaging examinations. The cyst is filled with serous or non-serous fluid. Recognition of the surrounding ectopic splenic tissue is the key point to diagnose ECIPAS. However, no preoperative examination was able to make a definite diagnosis. Almost all the patients (96%) received surgical treatment, due to the suspicion of pancreatic malignant or potentially malignant cystic tumor, especially mucinous cystic neoplasm (MCN).

CONCLUSIONS

Although seldom encountered, ECIPAS should be considered as a differential diagnosis for pancreatic cystic lesions, especially when solid component was detected. As a benign disease, unnecessary surgery should be avoided. Because it is difficult to make a definite diagnosis preoperatively by one single examination, multiple modalities may be required.

Intrapancreatic accessory spleen: a diagnostic dilemma

BACKGROUND

As intrapancreatic accessory spleen (IPAS) is rarely encountered during clinical practice, the aim of this review was to summarize the epidemiologic features, the diagnosis and treatment of IPAS.

METHODS

MEDLINE and EMBASE were searched for articles reporting on IPAS. Categorical variables were reported as frequency and percentage. Continuous variables were reported as median (range).

RESULTS

A total of 105 patients were included, of which 73% were detected incidentally. The male/female ratio was 1.23. The size of IPAS in patients who had previously undergone splenectomy was larger than that of patients without prior splenectomy (2.5 cm vs 1.5 cm; p = 0.020). No preoperative examination was able to make a definite diagnosis for all IPASs. More than half of the patients (55%) received surgical treatment, most of which (87%) were suspected as pancreatic neuroendocrine tumors (p-net) preoperatively.

CONCLUSIONS

Although rare, IPAS should be considered in the differential of patients with suspected incidental p-net, especially if there has been a past history of splenectomy. Preoperative diagnosis is important as unnecessary surgery can be avoided. As it is difficult to make a definite diagnosis of IPAS by one single examination, multiple techniques may be required.