Acinar cell carcinoma variants

Acinar cell cystadenocarcinoma

Acinar cell cystadenocarcinomas are rare, grossly cystic neoplasms with cytoarchitectural features of acinar cell carcinomas {229, 825, 739, 1815}.

Mixed acinar-endocrine carcinoma

Rare neoplasms have shown a substantial (greater than 25%) proportion of more than one cell type. These neoplasms have been designated 'mixed carcinomas', and, depending upon the cell types identified, as 'mixed acinar-endocrine carcinoma', 'mixed acinar-ductal carcinoma', or 'mixed acinar-endocrine-ductal carcinoma' {997, 1369, 2015}. Of these, the best characterized is the mixed acinar-endocrine carcinoma {997}. In many mixed acinar-endocrine carcinomas, the evidence for divergent differentiation is only provided by immunohistochemical staining. Although different regions of the tumours may suggest acinar or endocrine differentiation morphologically, many areas have intermediate features, and immunohisto-chemistry generally shows a mixture of cells expressing acinar or endocrine markers (or both). In exceptional cases, however, there is also morphological evidence of multiple lines of differentiation,

Fig. 10.30 Acinar cell carcinoma. Solid pattern with uniform round nuclei.

with some regions exhibiting obvious aci-nar features and other areas endocrine features. Most reported acinar-endocrine carcinomas have been composed predominantly of acinar elements based on the proportion of cells staining immuno-histochemically {997}. There are insufficient cases recorded to suggest that the biological behaviour of mixed acinar-endocrine carcinomas differs from that of pure acinar cell carcinomas.

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