4 Other Intestinal Neoplasms

Case 4.1 Carcinoid Tumor of the Ileocecal Region

The large section in Figure 4.1 demonstrates multiple round foci of tumor tissue invading all the layers of the wall of the small intestine. The section in fact corresponds to the ileocecal region and also contains structures of the colon (located in the left upper corner of the image). Microscopy revealed structures of carcinoid tumor corresponding to the red-colored areas in Figure 4.1c. The tumor originated in the mucosa of the small intestine, as demonstrated in Figure 4.1a, which is a microscopic magnification of the area marked with the yellow rectangle in the schematic image (Fig. 4.1c). The tumor cells exhibited a strong immunohistochemical reaction with the endocrine marker chromogranin A (Fig. 4.1b). Some lymph nodes free of metastasis were also present in the specimen (marked with green arrows in Fig. 4.1c). The intestinal wall was thickened as a result of hypertrophy of the lamina muscularis propria, a typical phenomenon associated with carcinoid tumor. A deep ulceration is also seen at the distal end of the specimen.

Fig. 4.1a

Fig. 4.1b

Fig. 4.1c Schematic guide to the details in the large section in Fig. 4.1.

Practical points

• By including a transection of the entire tumor, large histologic sections provide an advantageous diagnostic tool in assessing the extent of tumor growth.
  
• Large sections allow examination of an extensive area of the mesocolon/mesenterium, which facilitates documenting locoregional metastatic tumor spread.

Case 4.2 Primary Malignant Lymphoma of the Colon

The large histologic section in Figure 4.2 demonstrates the typical appearance of a malignant lymphoma in the intestine: a diffuse, monotonous infiltrate leading to thickening of the intestinal wall due to discohesive growth of the tumor cells. The same monotonous histologic picture, seen in Figure 4.2a, could be obtained by magnifying any part of the tumor. This lymphoma was made up of atypical B-lymphocytes (as shown by immunohistochemical reaction with the B-cell marker CD20, Fig. 4.2b) and contained only a few reactive T-lymphocytes (Fig. 4.2c, immunohistochemical reaction with CD3). The green arrow in Figure 4.2d indicates the zone of transition between the normal intestinal structures and the tumor, the yellow arrow indicates areas of tumor necrosis. These areas may explain the results of the preoperative histologic examination in this case. Interestingly, there are reactive lymph nodes free of lymphoma in the immediate vicinity of the tumor (encircled in Fig. 4.2d).

Fig. 4.2a

Fig. 4.2b

Fig. 4.2c

Practical points

• A diffuse solid thickening of the intestinal wall may indicate the presence of malignant lymphoma.
  
• Non-involved lymph nodes may be present in the immediate vicinity of a large mass of lymphoma, carrying the risk of a false-negative diagnosis when sampled for histologic examination.

Fig. 4.2 Large-section histology image of a primary malignant lymphoma of the colon.

Fig. 4.2d Schematic guide to the morphologic details in the large section on Fig. 4.2.

Case 4.3 Intestinal Lymphoma

The large histologic section in Figure 4.3 demonstrates another case of malignant lymphoma, this time infiltrating the wall of the small intestine. The diffuse thickening of the intestinal wall is very well seen. As indicated by the yellow arrow in the schematic image (Fig. 4.3b), the intestinal wall was perforated due to ulceration and necrosis of the tumor tissue. Necrotic areas were also present in other parts of the tumor; the most obvious of them is marked with a red rectangle in the schematic image. Figure 4.3a is a microscopic magnification of a detail from the tissue of the high-grade lymphoma with large atypical cells containing prominent nucleoli.

Fig. 4.3a

Fig. 4.3b Schematic guide to the morphologic details in the large section in Fig. 4.3.

Practical points

• Massive necrosis of malignant lymphoma tissues is frequent and may lead to perforation of the intestinal wall.

Case 4.4 Intestinal Lymphoma with Massive Necrosis

The large histologic section in Figure 4.4 demonstrates a primary malignant lymphoma of the colon infiltrating the ileocecal region. The massive infiltration of the blue-stained tumor tissue is well seen in the mesenterium. There are large areas of tumor necrosis (indicated by the yellow-colored areas in Fig. 4.4e). The mucosa was only partly preserved and mostly ulcerated. Figure 4.4a is a microscopic magnification of the area indicated with the red rectangle in Figure 4.4e and demonstrates the intestinal mucosa on the right side of the image and the tissue of the lymphoma on the left side. Absence of a reaction with the epithelial marker cytokeratin Cam5,2 (illustrated in Fig. 4.4b) indicates a non-epithelial tumor (the rest of the normal epithelium is stained brown). Figure 4.4c, d is a high-power microscopic magnification of the lymphoma and also proves the aggressive nature of the tumor, which shows perivascular and intramuscular infiltration. Note the enlarged reactive lymph node (marked with a blue arrow in Fig. 4.4e). Massive necrosis of the tumor tissue may appear in lymphomas as well as in carcinomas and can lead to the formation of pseudolumen, as was already demonstrated in Case 3.14.

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