Page 418 - Concise Pathology for Exam Preparation ( PDFDrive )

14 The Oral Cavity and Gastrointestinal Tract 403

Clinical Features

• Abdominal pain
• Anorexia
• Anaemia
• Weight loss
• Vomiting
• Dysphagia due to involvement of cardiac end
• Obstructive symptoms due to involvement of pylorus
• All gastric carcinomas eventually penetrate the serosa to spread to local and distant
lymph nodes. Other proposed mechanisms of spread include transperitoneal, lym-
phatic, haematogenous, via remnants, falciform ligament, etc.
• May frequently metastasize to supraclavicular lymph nodes as the first clinical manifes-
tation of an occult neoplasm (Virchow lymph node) or to the periumbilical region to
form a subcutaneous nodule (Sister Mary Joseph nodule).
• Another common site for visceral metastasis is bilateral ovaries (Krukenberg tumour).
Although uncommon, metastatic adenocarcinoma to the ovary may be seen in associa-
tion with carcinoma stomach, breast, pancreas and gallbladder.
Q. Write briefly on gastrointestinal stromal tumours (GISTs).

Ans. Gastrointestinal Stromal Tumour (GIST)
• Most common mesenchymal tumour of GIT; most common location is stomach.
• It is male predominant; is seen in the fifth and sixth decades and can present as a triad
called Carney’s triad (gastric GIST, paraganglioma and pulmonary chondroma).
• Origin from interstitial cells of Cajal (which are the pacemaker cells for gut peristalsis
and are located in muscular propria).
• Associated with a gain of function mutation of the gene encoding for tyrosine kinase
c-kit (receptor for stem cell factor). This leads to constitutional activation of c-KIT
which in turn activates the RAS pathway to promote cell proliferation.
• Patient usually presents with an abdominal mass. CT is the best diagnostic modality.
• GISTs may be as large as 30 cm, solitary, well circumscribed, fleshy, submucosal or
subserosal masses. When large they may cause ulceration of the overlying mucosa.
• Sections show mainly spindle cells or epithelioid cells or an admixture of the two cell
types. Tumour cells express c-KIT (CD117) and CD 34.
• Prognosis of the tumour is dependant on tumour size (recurrence and metastasis as-
sociated with a size . 5 cm); mitoses and location (intestinal GISTs are more aggressive
than gastric GISTs).

SMALL INTESTINE

• Small intestine varies in length from 4–7 meters. Although it is 4–5 times longer
than large intestine, it is referred to as ‘small’ due to its comparatively smaller
diameter.
• The average diameter of the small intestine of an adult human measures approximately
2.5–3 cm, and the large intestine measures about 7.6 cm in diameter.
• It is divided into three structural parts:
• Duodenum
• Jejunum
• Ileum

Duodenum
• Mucosa: Consists of epithelium, lamina propria and a thin muscularis mucosa; epithe-
lium is simple columnar with goblet cells and Paneth cells.
• Submucosa: Composed of Brunner’s glands within fibrous connective tissue, which also
has Meissner’s plexus.
• Muscularis externa: Two layers of smooth muscle, namely, longitudinal and circular.
Auerbach’s plexus is found between them.

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