Pancreatoblastoma : Microscopic
Comments:
Microscopic Features of Pancreatoblastoma (continued from previous image): Squamoid nests are an important diagnostic feature of pancreatoblastoma. They are variable in size and range from islands of epithelioid cells with eosinophilic cytoplasm to regular whorled nests of spindle cells with squamoid features. They show a peripheral to central gradient of maturation and may form intercellular bridges and keratin pearls. The nuclei of squamoid nests are uniform, round to oval, and larger than those in the surroundings. Many nuclei show clearing due to intranuclear accumulation of biotin (see images 9 and 10). Squamoid nests are not distributed uniformly and may be absent in small biopsies. The stroma is myxoid and variably cellular. It may uncommonly show heterologous elements such as bone and cartilage. Some cases show mucinous glands as well as foci with primitive small round blue cells. About this image: A large squamoid nest is surrounded by a sheet of small uniform basophilic cells. Numerous rosettes and acinar structures are embedded within the sheet.