In situ demonstration of parathyroid hormone-related protein mRNA in sclerosing hepatic carcinoma.

A 69-year-old man had a hepatic tumour occupying the left and half of the right lobe, with portal vein thrombus. There were hypercalcaemia and hypophosphataemia with increased nephrogenous cyclic adenosine monophosphate; bone metastases were excluded. Serum parathyroid hormone-related protein (PTHrP) was elevated, but no increase in intact parathyroid hormone (PTH) or vitamin D3 metabolites was found. At autopsy the histological features were typical of sclerosing hepatic carcinoma. By immunohistochemistry PTHrP was detected in cancer cell nests but not in the fibrous stroma. PTHrP transcripts were demonstrated by in situ hybridization using a polymerase chain reaction (PCR)-derived single-stranded DNA probe. Tumour cells expressed AE1 and CA19-9 (markers for cholangioepithelium) and CEA (for bile canaliculi). Electron microscopy revealed microvilli on the apical surface, and secretory granules 100 nm in diameter were observed. These findings indicate that this case is one of cholangiocellular sclerosing hepatic carcinoma. The interaction between cancer and stromal cells may be the cause of PTHrP overexpression.