Page 433 - Concise Pathology for Exam Preparation ( PDFDrive )

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418 SECTION II Diseases of Organ Systems

• Hormone produced (bradykinin, serotonin, histamine and prostaglandins)
• Site of origin: foregut (pancreas, stomach and duodenum), midgut (jejunum, ileum,
appendix and ascending colon) or hind gut (transverse colon, descending colon and
rectum)

Gross Morphology
• Small button-like submucosal elevation with intact or ulcerated overlying mucosa
• Ileal and gastric carcinoids are multiple, whereas appendiceal carcinoids are solitary and
usually involve the tip of the organ

Microscopic Features
• Tumour cells are uniform and monotonous in appearance, forming discrete islands,
glands, cords or trabeculae.
• They have scanty cytoplasm and round-to-oval nucleus with fine stippled chromatin.
• Mitoses is infrequent and cellular atypia is uncommon.
• Other features: Presence of membrane-bound secretory granules (or dense core granules),
containing chromogranin A, synaptophysin, neuron-specific enolase, etc.

Characteristic Features of Carcinoids in Specific Locations
Terminal Ileum
• Peak involvement in seventh decade
• Female predominance
• Multicentric
• Metastasize widely

Appendix
• Most common gut carcinoid
• Affects patients in the third and fourth decades of life
• Usually solitary
• Behave like locally malignant tumours/metastasis is rare (rectal and appendiceal carci-
noids, almost never metastasize)
Hind Gut Carcinoids
• Constitute 10–20% of all cases
• Involve mainly rectum and colon

Foregut Carcinoids
• Argentaffin-negative
• Seen in stomach, duodenum and oesophagus

Carcinoid Syndrome
Salient Features
• It is present in 1% of all carcinoid tumour patients.
• More common in patients in whom the tumour has widely metastasized, particularly to
the liver. Loss of liver function is essential for the syndrome to manifest, as liver nor-
mally converts active 5-HT (5-hydroxytryptamine or serotonin) into its inactive form
5-HIAA (5-hydroxy indole acetic acid).
• Secretory product mainly responsible for the syndrome is 5-HT; histamine, bradykinin,
prostaglandins, etc., may also contribute.
Clinical Presentation
• Cutaneous flushes and cyanosis (vasomotor disturbances)
• Diarrhoea, cramps, nausea and vomiting (due to intestinal hyper motility)

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