A light and electron microscopic study of an ovarian and rectal carcinoid.

An ovarian and rectal carcinoid within the same person is described. The ovarian carcinoid is non-argentaffinic with typical regular granules. The rectal tumour consists of two types of APUD cells, some argentaffinic and diazo-positive, whilst others are non-argyrophilic. These features are mirrored ultrastructurally, some cells containing the large pleomorphic argentaffinic granules while others have smaller regular granules. In addition, focal aggregates of microfilaments were found in both tumour types. These findings are discussed in terms of the APUD concept. The similarities of the APUD tumour cells to D1 APUD cells of the duodenum is highlighted, and an alternative explanation for their derivation is proposed.