Multicystic pancreatic hamartoma: a distinctive lesion with immunohistochemical and ultrastructural study.

A multicystic pancreatic hamartoma is reported in a 20-month-old female who presented with abdominal pain and distention. This appears to be a distinctive lesion not previously characterized in the English language literature. The 9-cm mass consisted of large, irregular lobules of well-formed pancreatic acini admixed with fibrous tissue and fat. Cystically dilated ducts of variable caliber lined by benign epithelium were present. Endocrine cell islets were not evident. Immunohistochemistry and ultrastructural examination illustrated insulin-producing cells diffusely throughout the exocrine tissue as single cells or in small groups. Cells producing other pancreatic hormones were markedly decreased when compared with an age-matched control pancreas and were similarly dispersed. The patient was alive and well without tumor 9 months later. This entity may provide an unusual opportunity for insight into pancreatic organogenesis and pancreatic cellular differentiation.