ATP binding cassette subfamily D member 1: A highly sensitive diagnostic marker for solid pseudopapillary neoplasm of...

Solid pseudopapillary neoplasm of pancreas (SPN) is a rare low-grade malignant pancreatic tumor. The morphology of SPN exhibits considerable diversity. Accurate diagnosis is crucial due to the morphological similarity of SPN to other pancreatic tumors, including pancreatic neuroendocrine tumors (NETs), acinar cell carcinoma (ACC) and pancreatoblastoma (PB), especially in the preoperative biopsy specimen. Image-guided biopsy techniques are essential for preoperative diagnosis, but the limited tissue in biopsy samples can complicate the diagnosis of SPN from other tumors. In this study, we evaluate the diagnostic utility of ATP Binding Cassette Subfamily D Member 1 (ABCD1), a novel immunohistochemical (IHC) marker previously identified in surgically resected SPN specimens, for distinguishing SPN in biopsy samples. We analyzed biopsy samples from a cohort of 55 SPN patients (55 biopsy samples and 6 paired surgical resected samples) and compared them with samples from 61 pancreatic ductal adenocarcinoma (PDAC), 90 NET, 13 intraductal papillary mucinous neoplasm (IPMN), 7 ACC and 3 PB patients from four institutions. Our findings show that ABCD1 positively marks SPN biopsy samples consistently as surgical resected samples, with 100% overall positivity and 96.37% exhibiting moderate to strong expression. In contrast, moderate to strong ABCD1 expression was significantly lower in PDAC (3.28%) and NET (6.66%). However, strong expression was observed in 57.14% of acinar cell carcinomas (ACC). Furthermore, ABCD1 complements β-catenin in cases where nuclear β-catenin staining is ambiguous (100% ABCD1 positivity). ROC curve analysis revealed that ABCD1 exhibits excellent diagnostic performance for distinguishing SPN from other pancreatic tumors, achieving a sensitivity of 96.36% and a specificity of 93.10%, establishing it a reliable complementary diagnostic marker in biopsy samples. These results suggest that ABCD1 could serve as a valuable tool for the accurate preoperative diagnosis of SPN, thereby improving clinical management and patient outcomes.