Abdomen / Pelvis for Monday, June 1st, 2026

Contributed by Amsterdam University Medical Center (AUMC).
Evita van Amerongen, and Rick van Rijn.

History

A 16-year-old male adolescent with an unremarkable medical history was referred by his general practitioner to the radiology department for lumbar spine radiography due to chronic low back pain. The symptoms had been present for approximately 4–5 months and showed no improvement despite conservative treatment with physiotherapy.

Images (Click any image to enlarge)

PA Lumbosacral Spine X-ray. No significant osseous pathology. Incidental finding: just superior to the left iliac crest, within the retroperitoneum (as shown on the lateral radiograph), a well-circumscribed spherical lesion with subtle wall calcifications measuring approximately 6.1 × 5.5 cm. Ultrasound was performed.
Lateral Lumbosacral Spine X-ray
Abdominal ultrasonography demonstrated a well-defined, encapsulated heterogeneous mass with mixed solid and cystic components, measuring 5.1 × 4.4 × 4.6 cm. A dubious doppler-flow signal was detected.
Longitudal axis ultrasound through mass. The mass seems to originate from the pancreatic tail (claw-sign).
Transversal axis ultrasound through mass.

Question

What is the most likely diagnosis?

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Correct answer

Solid Pseudopapillary Epithelial Neoplasm (SPEN)

Discussion

The patient was referred to a tertiary care center specialized in pediatric oncology with a suspected diagnosis of solid pseudopapillary epithelial neoplasm (SPEN). Diagnostic uncertainty existed due to the patient’s age and male sex. However, a percutaneous biopsy with subsequent histopathological examination confirmed the diagnosis of SPEN. 

Solid pseudopapillary epithelial neoplasm (SPEN), also known as Frantz or Hamoudi tumor, is a rare, low-grade malignant pancreatic neoplasm. It accounts for approximately 6–17% of all pancreatic tumors in the pediatric population and for about 1–2% of pancreatic tumors overall. Due to its indolent growth pattern, SPEN is frequently asymptomatic at presentation and is often discovered incidentally. Routine laboratory investigations are typically unremarkable, as the tumor does not usually produce endocrine or exocrine pancreatic hormones.

SPENs have a characteristic appearance on imaging and are most commonly located in the body or tail of the pancreas. On ultrasound, SPENs typically appear as well-defined, heterogeneous pancreatic masses with mixed solid and cystic components. Internal septations, areas of hemorrhage or degeneration, and a capsule-like border may be observed. Doppler imaging usually demonstrates limited to moderate internal vascularity.

On computed tomography (CT), a distinguishing feature from other pancreatic neoplasms is that SPENs tend to enhance similarly to the surrounding pancreatic parenchyma after contrast administration.

Magnetic resonance imaging (MRI) is generally considered superior to CT for the evaluation of SPENs. On MRI, these tumors usually appear heterogeneous, with variable signal intensity on T1-weighted images and high signal intensity on T2-weighted images. The capsule is often visible as a hypointense rim surrounding the lesion.

An epidemiological characteristic of SPEN is its strong female predominance, with a reported male-to-female ratio of approximately 1:10. The tumor most commonly affects young individuals, with a mean age at diagnosis of approximately 28 years in females and 18 years in males, although cases have been reported across a wide age range, from childhood to late adulthood (8–67 years). The etiology of SPEN remains uncertain.

SPEN has distinctive histopathological and immunohistochemical features. Macroscopically, these tumors are typically well circumscribed and surrounded by a thick fibrous capsule. Smaller lesions (<3 cm) are predominantly solid, whereas larger tumors (>3 cm) commonly show a mixed solid and cystic architecture, often accompanied by areas of necrosis and intratumoral hemorrhage. Microscopically, the presence of a pseudopapillary growth pattern (characterized by poorly cohesive tumor cells arranged around delicate fibrovascular cores resulting from degeneration of tumor cell clusters) is considered pathognomonic for SPEN.

Although SPEN is generally regarded as a low-grade malignant neoplasm, malignant behavior has been reported in approximately 10–15% of cases. Despite its malignant potential, the prognosis of SPEN is excellent, with reported overall survival rates exceeding 97.6%, even in the presence of metastatic disease. Complete surgical resection remains the cornerstone of treatment and is generally curative.

The patient was scheduled for a spleen-preserving distal pancreatectomy. The procedure was completed without intraoperative complications. Postoperatively, the patient developed a splenic infarction. The postoperative course was otherwise uneventful, and the patient was discharged a few days later in good clinical condition and free of pain.

Differential diagnosis

Pancreatoblastoma is considered less likely, as the lesion is surrounded by a thick rim or capsule with calcifications, which is generally a more benign imaging feature. In addition, the absence of clear diffusion restriction and the lack of invasion into surrounding structures further argue against a more aggressive or malignant process.

Pancreatic neuroendocrine tumor (pNET) is also considered less likely, as there was no expression of neuroendocrine markers. Moreover, pNETs typically present as more solid and homogeneous lesions with evident diffusion restriction, usually lacking a capsule and hemorrhagic components. They also characteristically demonstrate arterial phase hyperenhancement on contrast-enhanced imaging; however, contrast-enhanced imaging was not performed in this case.

A hydatid cyst is likewise considered less likely, as the lesion did not demonstrate characteristic features such as daughter cysts or internal membranes. In addition, hydatid cysts are usually completely cystic in appearance. Furthermore, pancreatic involvement is very rare for this type of cyst.

Additional images

Axial T1-w
Coronal T2-w
Axial T2FS
DWI
ADC

References

  • Paluri RK, John TA, Anastasopoulou C, et al. Solid Pseudopapillary Epithelial Neoplasm (SPEN) of the Pancreas. [Updated 2024 Jan 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544335/
  • Gandhi D, Sharma P, Parashar K, Kochar PS, Ahuja K, Sawhney H, Sharma S. Solid pseudopapillary Tumor of the Pancreas: Radiological and surgical review. Clin Imaging. 2020 Nov;67:101-107. doi: 10.1016/j.clinimag.2020.06.008. Epub 2020 Jun 9. PMID: 32559679.
  • Qiu L, Trout AT, Ayyala RS, Szabo S, Nathan JD, Geller JI, Dillman JR. Pancreatic Masses in Children and Young Adults: Multimodality Review with Pathologic Correlation. Radiographics. 2021 Oct;41(6):1766-1784. doi: 10.1148/rg.2021210008. PMID: 34597223.
  • Xu YC, Fu DL, Yang F. Unraveling the enigma: A comprehensive review of solid pseudopapillary tumor of the pancreas. World J Gastrointest Oncol. 2024 Mar 15;16(3):614-629. doi: 10.4251/wjgo.v16.i3.614. PMID: 38577449; PMCID: PMC10989376.
  • Fleming AM, Hendrick LE, Yakoub D, Abdelhafeez H, Deneve JL, Langham MR Jr, Glazer ES, Davidoff AM, Merchant NB, Dickson PV, Murphy AJ. Malignant Solid Pseudopapillary Neoplasm of the Pancreas: An Orthogonal Analysis. Ann Surg Oncol. 2024 Jan;31(1):475-487. doi: 10.1245/s10434-023-14343-0. Epub 2023 Sep 28. PMID: 37768414.