A case of clear cell variant of solid-pseudopapillary tumor of the pancreas in an adult male patient.

A clear cell variant of solid-pseudopapillary tumor (SPT) of the pancreas was initially reported in 2006 as a tumor that arose in the pancreatic body and tail in young adults; to date, only 4 cases of this entity have been reported. Here, we present the case of a 58-year-old man with clear cell variant of SPT with distinctive clinicopathologic features. The tumor was well demarcated, was 2.6 cm in size and mostly composed of multivacuolated clear cells with solid growth, and exhibited the characteristic immunohistochemical positivity of β-catenin in the cytoplasm and nuclei of the neoplastic cells. In contrast to classical SPT with nuclear positivity, this case was negative for E-cadherin. Direct DNA sequencing of exon 3 of β-catenin gene demonstrated a single amino acid substitution (serine to phenylalanine) in codon 37, which is the phosphorylation site by GSKβ and frequently found in classical SPT. Electron microscopy demonstrated enlarged mitochondria and endoplasmic reticulum. Despite the fact that previous cases of clear cell variant of SPT arose mainly in the pancreatic body and tail in female young adults (age, 26-32 years), this case suggested that it is possible for a clear cell variant of SPT to arise in the pancreatic head in a middle-aged man. Because the recognition of the clear cell variant of SPT is important for the appropriate diagnosis of primary pancreatic tumor, the present case with its distinctive characteristics may provide new information for a more profound understanding of the pancreatic SPT.