Mixed endocrineexocrine neoplasms

This term is used for certain tumours of the appendix that show features of both glandular and endocrine differentiation, i.e. goblet cell carcinoid, tubular carci-noid and mixed carcinoid-adenocarcino-mas {2059, 1254}.

Goblet-cell carcinoid. This tumour is characterized by a predominant submu-cosal growth. It typically invades through the appendiceal wall in a concentric manner that does not produce a well-defined tumour {209}. The mucosa is characteristically spared, with the exception of areas of connection of tumour nests with the base of the crypts. The tumour is composed of small, rounded nests of signet-ring-like cells resembling normal intestinal goblet cells, except for nuclear compression. Lumens are infrequently observed. Lysozyme-positive Paneth cells as well as foci resembling

Fig. 5.13 Small cell carcinoma arising in an appendiceal tubulovillous adenoma.

Brunner glands may be present {2059, 790}. Mucin stains are intensely positive within goblet cells and extracellular mucin pools {790}. Argentaffin and argy-rophil cells, sparse or forming small nests, are identified in 50% and 88% of cases, respectively {2059}. Immunohistochemically, the endocrine cell component is positive for chromo-granin A, serotonin, enteroglucagon, somatostatin, and/or PP {790, 725}. The goblet cells express CEA. On ultrastructural examination, both dense core endocrine granules and mucin droplets are found {442, 725}. Both elements are occasionally present within the cytoplasm of the same cell {442, 790}. Tubular carcinoid. This tumour is often misinterpreted as a metastatic adenocar-cinoma, because it does not resemble the typical carcinoid and shows little contact with the mucosa. It is composed of small, discrete tubules, some with inspissated mucin in their lumen. Short trabec-ular structures are frequent, but solid nests are generally absent. In sparse cells or in small groups of tumour cells, the argentaffin reaction is positive in 75%

Was this article helpful?

0 0

Post a comment