Liver heterotopia in the head of a patient with osteosarcoma of the maxilla. A paracrine tumor-induced hepatogenesis?

Heterotopia of liver tissue is uncommon. It has been reported at various sites, more frequently near the orthotopic liver, including gallbladder, hepatic ligaments, omentum, and retroperitoneum, rarely within the diaphragm and the thoracic cavity, and never within the head. We report here a 22-year-old patient surgically treated for a maxillary osteosarcoma in which microscopic liver tissue islands were incidentally detected in the respiratory mucosa of the surgical margin. The islands comprised well-differentiated HepPar-1-positive hepatocytes and were surrounded by cytokeratin-7- and cytokeratin-19-positive bile duct-like structures. This case, which is unique in the medical literature, may suggest an inductive paracrine effect of the osteosarcoma cells by secretion of factors promoting hepatocyte specification of primitive endodermal progenitors and subsequent liver morphogenesis.