Intrapancreatic accessory spleen: Evaluation with CT and MRI

Intra pancreatic accessory spleen mimicking pancreatic insulinoma: a case report

Accessory spleens are a congenital anomaly caused by abnormal fusion during embryonic development, leading to the presence of splenic tissue in unusual locations, such as the tail of the pancreas. Their pronounced arterial enhancement can cause them to be mistaken for a neuroendocrine tumor, particularly an insulinoma. We report the case of a 61-year-old patient with recurrent hypoglycemia who was referred for suspected neuroendocrine tumor.

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.

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.

Intrapancreatic accessory spleen: An imaging enigma

The pancreatic tail is an uncommon location for the accessory spleen. Although it is a benign entity, it can mimic and get misdiagnosed as a pancreatic tumor which can lead to unnecessary biopsy and surgery. Here, we present a case who was detected to have a tail of pancreas mass. On CT and MRI, it showed similar density, signal intensity, and matching enhancement pattern with the orthotopic spleen. The ADC value of the mass was found to be similar to that of the spleen and significantly less than that of normal pancreas. A diagnosis of intrapancreatic accessory spleen was hence made and the patient was followed up after 6 months on MRI. No change in lesion morphology and size was noted. Thus, intrapancreatic accessory spleen should be kept in mind as a differential diagnosis while reviewing a case with pancreatic mass.