3 Advanced Colorectal Cancer

Case 3.1 Infiltrating Colon Carcinoma, Dukes B

Infiltration of the tumor structures beyond the level of the muscularis propria into the subserosa or into the pericolic/ perirectal tissue (as illustrated in Fig. 3.1a) indicates B stage in Dukes’ classification. Many other classification systems, including the TNM classification, recognize this level of infiltration as a crucial unfavorable prognostic factor. As was already demonstrated, a large histologic section, taken in the plane of the deepest infiltration of the tumor, shows the level of infiltration without the aid of a microscope. The large section shown in Figure 3.1 demonstrates an infiltrating carcinoma of the cecum, corresponding to the red-colored area in the schematic image (Fig. 3.1b). The deepest tumor structures infiltrating into the fatty tissue are microscopically magnified in Figure 3.1a. Note the reactive lymph nodes (indicated with green arrows in Fig. 3.1b). Since the tumor developed in the cecum, a transection of the terminal part of the ileum (indicated with the yellow arrow in Fig. 3.1b) was also included in the large section.

Fig. 3.1a

Fig. 3.1b Schematic guide to the morphologic details in the large section in Fig. 3.1.

Practical points

• Taken in the plane of the deepest invasion, the large histologic section reliably demonstrates the level of primary tumor growth.
  
• Inclusion of a large area of the pericolic/perirectal tissue is a further advantage of large histologic sections, which allow the pattern and extent of the invasion to be easily assessed.

Case 3.2 Rectal Carcinoma That Developed in a Villous Adenoma

In this particular case, the large histologic section (Fig. 3.2) demonstrates a villous adenoma covering the anterior part of the rectal circumference and an invasive carcinoma that developed in the adenoma covering the posterior half. The villous structures of the adenoma (corresponding to the area of the blue circle in Fig. 3.2e) are also seen magnified in Figure 3.2a. The interface of the structures of the adenoma and the carcinoma is microscopically magnified in Figure 3.2b, corresponding to the area of the red rectangle in the schematic image (Fig. 3.2e). The cancer infiltrated beyond the level of the lamina muscularis propria, interrupting the muscle layer at several points, two of which are magnified in Figure 3.2c, d (corresponding to the green and yellow rectangles in the schematic image, Fig. 3.2e, respectively). The blue arrow indicates the free mesorectal resection margin. A narrow white line in Figure 3.2e marks the border between the adenoma (under the line) and the carcinoma (above the line).

Fig. 3.2a

Fig. 3.2b

Fig. 3.2c

Fig. 3.2d

Practical points

• The large histological sections facilitate the assessment of the mesorectal margin.
  
• The spatial and quantitative relation of the carcinoma to the pre-existent adenoma is also easy to demonstrate using this technique.

Fig. 3.2 Large-section histology image of a rectal carcinoma developed in a villous adenoma.

Fig. 3.2e Schematic guide to the morphologic details in the large section in Fig. 3.2.

Case 3.3 Rectal Carcinoma, Dukes C

The large histologic section in Figure 3.3 demonstrates an advanced rectal carcinoma (corresponding to the red-colored area in the schematic image, Fig. 3.3b), which had developed in a tubulovillous adenoma. The rests of the adenoma are well seen on the periphery of the tumor. The cancer infiltrated through the muscular wall following the perivascular spaces. Examination of the tumor after preoperative irradiation showed some regression of the cancer as well as peritumoral fibrosis. The two lymph nodes in the specimen (marked with the blue arrows in Fig. 3.3b) were free of metastases. However, the third lymph node (marked with the yellow rectangle) contained a necrotic mass corresponding to a necrotic metastasis after irradiation. This node is histologically magnified in Figure 3.3a.

Fig. 3.3a

Fig. 3.3b Schematic guide to the morphologic details in the large section in Fig. 3.3.

Practical points

• Taken in the plane of the deepest invasion, the large histologic section reliably demonstrates the level of primary tumor growth and allows the effects of irradiation to be assessed.

Case 3.4 Mucinous Carcinoma of the Colon

The mucinous carcinoma demonstrated in Figure 3.4 had also developed in a villous adenoma. Both the structures of the adenoma (some of them marked with yellow arrows in the schematic image, Fig. 3.4b) and the areas of the mucinous cancer (corresponding to the blue-colored area in the schematic image) are well seen in the large histologic section. The tumor infiltrated the pericolic fatty tissue. The cancer exhibited obvious intratumoral heterogeneity, as demonstrated in Figure 3.4a, which shows a microscopic detail from the area marked with the red rectangle in Figure 3.4b. Mucinous carcinoma in the colorectum is defined as a cancer with dominating mucinous structures (more than 50% of the tumor). The large histologic section allows proper assessment of the proportions of different tumor types in cases of heterogeneous tumors, and assists in proper tumor typing. It also helps in appreciating the difficulties in obtaining biopsies representative of the invasive part of the tumor, as in the present case.

Fig. 3.4a

Fig. 3.4b Schematic guide to the morphologic details in the large section in Fig. 3.4.

Practical points

• Inclusion of a transection of the entire tumor is a further advantage of large histologic sections, as the proportions of different tumor parts can be determined and heterogeneous tumors can be properly typed.

Case 3.5 Invasive Rectal Carcinoma, Dukes C

The large histologic section in Figure 3.5 demonstrates an invasive carcinoma (corresponding to the red-colored area in the schematic image, Fig. 3.5d), the rest of the tumor being tubulovillous adenoma filling the lumen of the large intestine. An enlarged, tumor-containing, necrotic lymph node is seen on the left upper edge of the image marked with the blue rectangle in Figure 3.5d and is histologically magnified in Figure 3.5a. Isolated foci of infiltrating tumor tissue without histologic evidence of residual lymph node structures in their surroundings are also seen in the mesorectum (partly marked in red and indicated with a blue double arrow in Fig. 3.5d; magnified microscopically in Fig. 3.5b). According to the TNM classification, if the foci have the round form and smooth contour of a lymph node, they should be classified as lymph node metastases. If they are irregular, as in this case, they should be classified as vascular invasion (V1 if seen only microscopically, V2 if seen upon examination with the naked eye). The isolated tumor foci should also influence the measurement of the surgical margin, as indicated with the blue double arrow in Figure 3.5d. In this case, additional lymph nodes are seen in the large section, one of them, marked with the yellow arrow, containing metastasis in the subcapsular sinus (Fig. 3.5c, upper edge of the image).

Fig. 3.5a

Fig. 3.5b

Fig. 3.5c

Practical points

• Large histologic sections allow examination of a large area of the mesorectum, and thus are an ideal tool for detecting isolated tumor foci in the fatty tissue.
  
• The isolated tumor foci, depending on their form, should be classified either as lymph node metastasis or as vascular invasion. These foci also influence the status of the surgical margins.

Fig. 3.5 Large-section histology image of a rectal carcinoma with lymph node metastases and isolated tumor foci in the perirectal fatty tissue.

Fig. 3.5d Schematic guide to the morphologic details in the large section in Fig. 3.5.

Case 3.6 Advanced Colon Carcinoma

The large histologic section in Figure 3.6 is very informative as it demonstrates the large exophytic and infiltrating carcinoma in the posterior parts of the cecum (corresponding to the red-colored area in the schematic image, Fig. 3.6c) together with a large area of the mesocolon. The tumor infiltrated the intestinal wall and the pericolic fatty tissue, partly forming continuous extensions, partly forming isolated tumor foci (also red-colored in Fig. 3.6c) lacking any connection with the main tumor mass. Some of the isolated tumor foci (marked with arrows in Fig. 3.6c) are round or oval shaped and have smooth contours. One of them (marked with the yellow arrow) is magnified in Figure 3.6a. This lesion represents a borderline structure between a metastatic lymph node and an isolated round tumor focus, as only a minimal rest of the lymphoid tissue is present in the central part of the lesion. However, this borderline image justifies classification of the smooth-contoured isolated tumor foci as lymph node metastases. Figure 3.6b is a microscopic magnification of the area of the blue rectangle in Figure 3.6c and demonstrates an irregular, isolated tumor focus partially with vascular invasion. Several enlarged lymph nodes containing metastatic tumor structures are also seen (green-colored in Fig. 3.6c).

Fig. 3.6a

Fig. 3.6b

Fig. 3.6c Schematic guide to the morphologic details in the large section in Fig. 3.6.

Practical points

• Isolated tumor foci in the mesocolon should be classified as lymph node metastasis if exhibiting a round shape and smooth contours similar to a lymph node.
  
• Isolated tumor foci with an irregular shape indicate a high probability of vascular invasion.

Stay updated, free articles. Join our Telegram channel

Join