Aggressive Metastatic Behaviour in Pancreatic Solid Pseudopapillary Neoplasm: A Series of Three Cases

Solid Pseudopapillary Neoplasms (SPNs) of the pancreas are rare low-grade malignant tumours predominantly affecting young women. Although its malignant potential is low, metastases- particularly to the liver can occur. Hereby, the authors present three unusual cases of pancreatic SPN in varied age groups are being presented - in a 17-year-old, 50-year-old and a 37-year-old female of which the all three cases were diagnosed as malignant SPN with metastases. The first case presented with abdominal pain and unusually huge palpable mass of greatest dimension of 18 cm with liver and peritoneal metastasis. Histopathology demonstrated high mitotic activity (approx. 40/10 hpf), capsular invasion, peripancreatic fat invasion, and metastatic deposits in both the liver and peritoneum, confirming malignant SPN. The second case presented with multiple liver Space-Occupying-Lesions (SOLs) which on Ultrasound-guided Fine-Needle Aspiration Cytology (FNAC) showed characteristic cytological features of SPN. The patient had a past history of distal pancreatectomy for SPN three years back. The cytologic features were suggestive of metastatic recurrence of SPN occurring after three years of primary disease, although there was no evidence of any recurrent tumour in the previous operation site in pancreas. The third case had undergone resection of pancreatic SOL for SPN which measured a maximum dimension of 24 cm and showed peripancreatic lymph node metastasis. This case is one of the largest documented SPN reported in literature. The malignant nature of the three cases were on the basis of liver and peritoneal metastasis in the first case, liver metastasis in the second case and peripancreatic lymph node metastasis in the third case. The first patient underwent surgical resection with no adjuvant therapy initiated at the time of reporting. The second patient was referred for oncology evaluation for systemic management of her metastatic recurrence. The third patient had an uneventful postoperative recovery and is currently under close follow-up. These three cases highlight the variable clinical spectrum of SPN including aggressive metastatic behaviour, exceptionally large tumour dimensions, and late recurrences. They also underscore the indispensable role of histopathology and immunohistochemistry in accurate diagnosis, and the importance of long-term follow-up even after apparently complete resection.