PMC8558400_01
Time axis of repeated surgery and targeted therapy for the metastatic pancreatic solid pseudopapillary neoplasm. Computed tomography scan showing multiple tumors in the peritoneum and retroperitoneum (white arrow) prior to sunitinib treatment after repeated surgery (A). Tumors rapidly increased in size 24 months after sunitinib treatment (B). There was a 52x36 mm, well-defined mass with heterogeneous contrast enhancement in the right lobe of the liver (white arrow) prior to evirolimus treatment after extended metastasectomy (C), which maintained tumor volume stability 15 months (D) and 22 months (E) after evirolimus treatment.
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The second metastasectomy was performed to remove recurrent nodules of the left adrenal gland (maximum size of 20 x 15 cm) on January 8, 2015 ( Figure 1 ). During the next 10 months the patient suffered some additional metastatic recurrences (maximum size of 55 x 35 cm) in her left adrenal gland and peritoneum ( Figure 1A ) before her first visit to our hospital on November 17, 2015. In the first quarter of 2018, the patient presented with some new metastatic lesions in the peritoneum, pelvis, and retroperitoneum, and the earlier lesions increased in size significantly ( Figure 1B ). Computed tomography (CT) scan revealed a well-defined hepatic encapsulated solid mass with cystic components but no calcification (maximum size of 52 x 36 cm,  Figure 1C ). The serial follow-up magnetic resonance imaging examination on March 2020 ( Figure 1D ) and October 2020 ( Figure 1E ) showed that the patient's tumor had partially resolved and remained stable for more than 22 months after the targeted treatment of everolimus.
Microscopic and immunohistochemical findings in peritoneal lesions of the metastatic solid-pseudopapillary neoplasms (SPN). (A), The tumor had a heterogeneous growth with predominantly pseudopapillary pattern (hematoxylin-eosin, original magnification x200). Note the capsular invasion (black arrow). (B), Vascular invasion (black arrow). (C), Nuclear positivity for beta-catenin. (D), Dot-like paranuclei positivity for CD99. (E), Negative for chromogranin A (CgA) expression in immuonstaining.
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The pathological analysis confirmed the metastatic nature of the SPN as capsular with very few capsular and vascular invasions ( Figure 2 ). In the late lesions, malignant histological features, such as peritumoral infiltration into the fat tissue (from the fourth lesion) and the organ, prominent capsular and vascular invasion were observed ( Figures 2A, B ). Figure 2C ). Furthermore, the average Ki-67 labeling index increased sharply (3%, 5-10%, and 15% in the third, fourth, and fifth metastatic lesions, respectively).