Solid-Pseudopapillary Neoplasm of the Pancreas: A 63-Case Analysis of Clinicopathologic and Immunohistochemical Features and Risk Factors of Malignancy

Abstract

Purpose: Solid-pseudopapillary neoplasm (SPN) of the pancreas, a rare tumor, has low malignant potential. However, some patients develop metastasis and recurrence after resection, with aggressive biological behaviors. This study aimed to explore the features and risk factors associated with the aggressive biological behaviors of SPNs.

Patients and methods: We retrospectively analyzed the clinicopathological and long-term follow-up data of 63 patients diagnosed with SPN at the First Affiliated Hospital of Bengbu Medical College between January 2007 and February 2019.

Results: Sixty-three patients presented atypical clinical symptoms. The median tumor size was 7.0 cm (range, 2.4-17 cm), and imaging features were solid and cystic or solid tumors with uneven density. Frequent and diffuse nuclear LEF1 protein expression (94.2%) was observed with LEF1 having a higher sensitivity and specificity. Overall survival significantly correlated with tumor size, Ki-67 index, and lymph node metastasis (P < 0.05).

Conclusion: SPN is a rare low-grade malignancy with a specific pseudopapillary structure. LEF1 is an effective biomarker of SPNs. Although SPNs generally display indolent biological behavior, a large tumor size, high proliferation index, and lymph node metastasis may be risk factors for the aggressive behavior and poor prognosis of SPN.

Keywords: LEF1; metastasis; overall survival; pancreatic tumor; retrospective study.

Figure 1

Histopathological characteristics of solid-pseudopapillary neoplasm (SPN) based on hematoxylin and eosin (H&E) staining. (A) The tumor cells have various shapes, forming clusters of different sizes with hemorrhage, cystic, and pseudopapillary structures (magnification, ×100). (B) The tumor is mainly a solid area, with less interstitial components (magnification, ×200). (C) The tumor cell cytoplasm is eosinophilic or lightly stained, the nucleus is oval, the chromatin is fine, and mitotic images are rare (magnification, ×400). (D) The tumor has a wide hemorrhagic area with cystic degeneration (magnification, ×200). (E) The cells distant from the blood vessels degenerate and fall off, and the tumor cells around the blood vessels surround the blood vessels to form pseudopapillary structures (magnification, ×200). (F) The tumor infiltrates surrounding normal pancreatic tissue (magnification, ×100).

Figure 2

Immunohistochemical staining (EnVision Method). (A and B) LEF1 is positively expressed in the nucleus of the tumor cells at ×100 and ×400 magnification, respectively. (C) LEF1 is positively expressed in the nucleus of the pancreatoblastoma tumor cells (magnification, ×400). (D) β-catenin is positively expressed in the nucleus and cytoplasm of the tumor cells (magnification, ×400). (E) Vimentin is positively expressed in the cytoplasm of tumor cells (magnification, ×200). (F) Ki-67 proliferation index of the tumor cells is low, and the nucleus is positively expressed (magnification, ×200).

Figure 3

Kaplan–Meier disease-free survival curves according to the (A) tumor size (P = 0.010), (B) Ki-67 index (P < 0.001), and (C) lymph node metastasis (P = 0.011).