1. APUDOMAS (Diffuse Endocrine System)
J. O. Ogunbiyi Department of Pathology University College Hospital Ibadan, Nigeria

2. Introduction
These are tumours of APUD cells. Some secrete the normal hormone of their presumptive cell of origin and are called orthoendocrine. Those secreting hormones of other apud cells are called paraendocrine tumours.

3. A high content of amines The capacity for amine precursor uptake
The APUD cells derive their name from the initial letters associated with their three most important properties:
A high content of amines
The capacity for amine precursor uptake
The presence of amino acid decarboxylase, which converts amino acids into amines.

4. They contain characteristic granules on electron microscopy
Cells with these properties have been grouped together as the APUD system.
They contain characteristic granules on electron microscopy
and secrete polypeptides, or amines, or both

5. The cells included here are:
The chromaffin cell system- These are found in the adrenal medulla and in association with the paravertebral plexuses.
The non-chromaffin cells of the paraganglia (Carotid body, glomus jugulare).
The argentaffin (Kultschitzky) cells ( found in the intestine). Similar cells occur in the salivary glands, pancreas, and bronchial mucosa. . The argyrophil cells. These are widely distributed in the intestine.

6. Other neuroectodermal cells are present in the stomach and small intestine
These are responsible for secretion of VIP, cholecystokinin, gastrin, 5HT, etc

7. They include
Pancreatic islet cells, Thyroid C cells, Parathyroid cells, Melanocytes, Hypothalamic neuroendocrine cells, Some cells of the anterior pituitary, and The autonomic neurons

8. The following syndromes are accompanied by apudomata

9. Hypoglycaemia (pancreatic ß-islet cell hypersecretion)
The glucagonoma syndrome
The Zollinger-Ellison syndrome (in which there is hyperplasia of the G cells of the pyloric antrum or of the B-cells of the pancreas).
The Verner-Morrison syndrome (pancreatic cholera)

10. WDHA (watery diarrhea, hypokaleamia, and achlorhydria) syndrome.
Non-ß islet cell tumour, SCLC, MCT, malignant carcinoid, mast cell tumours, and neuroblastoma. In all of these, there is XS VIP secretion

11. Cushing’s syndrome / (ectopic ACTH syndrome) consisting
hypokaleamia alkalosis, diabetes mellitus, hyperpigmented skin, muscle wasting with weakness.
May be found with SCLC, bronchial carcinoid, carcinoid of thymus, pancreatic islet cell tumour, MTC, pheo, ovarian carcinoma

12. The carcinoid syndrome.
Those of the foregut tend to be secretory and active unlike the hindgut ones that tend to be inactive

13. The somatostatin syndrome. D-cell tumours of the pancreas.
The MEN syndromes