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Figure 20.48 Colonic adenocarcinoma. A, Moderately differentiated. B, Mucin-secreting adenocarcinoma.

bowel wall as well as directly into the depth of the bowel STAGING AND PROGNOSIS. The prognosis of colorectal
wall to the serosa, pericolic fat, and sometimes into peritoneal cancer depends upon a few variables:
cavity. i) Extent of the bowel involvement
2. Lymphatic spread. Spread via lymphatics occurs rather ii) Presence or absence of metastases
commonly and involves, firstly the regional lymph nodes in iii) Histologic grade of the tumour CHAPTER 20
the vicinity of the tumour, and then into other groups of iv) Location of the tumour
lymph nodes like preaortic, internal iliac and the sacral lymph The most important prognostic factor in colorectal cancer
nodes. is, however, the stage of the disease at the time of diagnosis.
Three staging systems are in use:
3. Haematogenous spread. Blood spread of large bowel 1. Dukes’ ABC staging (modified Duke’s includes stage D as
cancer occurs relatively late and involves the liver, lungs, well).
brain, bones and ovary.
2. Astler-Coller staging which is a further modification of
CLINICAL FEATURES. Clinical symptoms in colorectal Duke’s staging and is most widely used.
cancer appear after considerable time. These are as follows: 3. TNM staging described by American Joint Committee is
i) Occult bleeding (melaena) also used.
ii) Change in bowel habits, more often in left-sided growth Table 20.12 and Fig. 20.49 sum up the features of staging The Gastrointestinal Tract
iii) Loss of weight (cachexia) classification and the overall 5-year survival rate in disease
iv) Loss of appetite (anorexia) stage.
v) Anaemia, weakness, malaise.
The most common complications are obstruction and B. Other Colorectal Malignant Tumours
haemorrhage; less often perforation and secondary infection Aside from colorectal carcinoma, other malignant tumours
may occur. Aside from the diagnostic methods like stool test which are encountered sometimes in the large bowel are
for occult blood, PR examination, proctoscopy, radiographic leiomyosarcoma (page 737) and malignant lymphoma (page
contrast studies and CT scan, recently the role of tumour- 559). Hindgut carcinoids may occur in the rectum and colon
markers has been emphasised. Of particular importance is (page 576).
the estimation of carcinoembryonic antigen (CEA) level
which is elevated in 100% cases of metastatic colorectal TUMOURS OF THE ANAL CANAL
cancers, while it is positive in 20-40% of early lesions, and
60-70% of advanced primary lesions. However, the test may Epithelial tumours of the anal canal are uncommon and may
have prognostic significance only and is not diagnostic of be combination of several histological types. Amongst the
colorectal cancer because it is positive in other cancers too benign tumours of the anal canal, multiple viral warts called
such as of the lungs, breast, ovary, urinary bladder and as condyloma acuminata are the only tumours of note.
prostate. CEA levels are elevated in some non-neoplastic Malignant tumours of the anal canal include the following:
conditions also like in ulcerative colitis, pancreatitis and 1. Squamous cell carcinoma (Fig. 20.50)
alcoholic cirrhosis. 2. Basaloid carcinoma