Malignant GISTs are generally larger than benign GISTs and tend to extend exophytically to the stomach rather than into it (Figs. 2-69 and 2-70). They also infiltrate the gastric wall as a polyp- oid nodular mass with frequent ulceration (Fig. 2-71). The c-kit (CD117) receptors are effectively targeted by c-kit tyrosine kinase inhibitors (imatinib), which have proved to be highly effective chemotherapeutic agents for malignant GISTs, particularly smaller (< 5 cm) tumors.
Lymphoma
The GI tract is the most common site for extranodal lymphoma (up to 30% of abdominal lymphomas). The stomach is the most common site, followed by the small bowel, and finally the colon. Esophageal involvement is very rare. Although there are many types of lymphoma (the World Health Organization currently lists 43 varieties), the most common lymphomatous GI tract disorders are non-Hodgkin† lymphomas and include those listed in Table 2-5,
with diffuse large B cell the most common. The stage is determined by the Ann Arbor classification (Table 2-6).
Primary gastric lymphoma is uncommon (about 2% of all lym- phomas), but metastatic lymphoma is much more common, and the stomach is the most common GI site for lymphoma. Most are B-cell, non-Hodgkin lymphomas, ranging from well-differentiated mucosa-associated lymphoid tissue (MALT) type to high-grade large-cell disease. Mantle cell and T-cell lymphomas are rarer recognized types. The latter can be difficult to distinguish from *Friedrich Ernst Krukenberg (1871-1946), German physician.
†Thomas Hodgkin (1798-1866), British physician and pathologist.
should be identified, and most tumors will be visualized once they become transmural and stage III and IV cancers develop (Fig. 2-61). Regional lymph nodes may be small and difficult to detect on CT, but their location in relation to the stomach should alert the radiologist to the diagnosis. PET imaging is sometimes used, not as a first-line investigation but rather as a tool for the evaluation of regional and remote metastases, particularly smaller lymphadenopathy (Figs. 2-61 and 2-62). Some tumors appear as if they are lower esophageal tumors, but they represent cardial tumors that invade into the lower esophagus (Fig. 2-62). Others present with the appearance of a leather-bottle stomach (also known as linitis plastica; see later in this chapter), which typically arises in the antrum and infiltrates along the gastric wall, producing a concentric narrow antrum (Figs. 2-63 and 2-64).
A rarer gastric carcinoma, known as scirrhous carcinoma, also typically arises in the antrum and produces a linitis plastica or leather-bottle appearance (Fig. 2-63). This may also extend more proximally to involve the gastric body (Fig. 2-65). Polypoid car- cinoma is less common and frequently ulcerates. Such tumors Figure 2-54. UGI series in a 40-year-old woman with a small mucosal
antral lesion due to ectopic pancreas (arrow).
Figure 2-55. Axial contrast-enhanced CT in a 49-year-old woman with
a 1.5-cm hypervascular intragastric mass (arrow) due to gastric carcinoid.
Figure 2-56. UGI series in a 64-year-old man with multiple nodular fill-
ing defects at the gastric cardia (arrow) due to gastric varices.
A
B
Figure 2-57. Axial (A) and coronal (B) contrast-enhanced CT in a 54-year-old man with chronic pancreatitis and multiple gastric varices (arrows).
t
able2-4
Staging of Gastric CarcinomaStage Findings
0 Carcinoma in situ; limited to mucosa 1A Transmucosal (5-year survival 85%)
1B Transmucosal and up to 6 regional lymph nodes involved or muscularis invaded
II Transmucosal with 7-15 regional lymph nodes involved or muscularis involvement with 6 regional lymph nodes or serosal involvement without regional lymph nodes IIIA Muscularis involvement with 7-15 adjacent nodes;
serosal invasion with up to 6 local nodes (5-year survival 50%); local organ invasion but no nodes IIIB Serosal involvement with 7-15 regional nodes IV Adjacent organs and at least 1 regional lymph node;
more than 15 regional nodes; distant metastases
Figure 2-58. UGI in a 66-year-old woman with thickened antral folds
and a small filling defect (arrow) on the distal lesser curve that was proved to be early gastric adenocarcinoma.
Figure 2-59. Barium UGI series in a 44-year-old man with fundal pol-
ypoid mass (arrow) due to gastric adenocarcinoma.
Figure 2-60. Axial noncontrast-enhanced CT in a 57-year-old man with a subtle 2-cm gastric mass (arrows) that was found to be gastric adenocarcinoma.
A
B
C
Figure 2-63. UGI series (A) and axial (B) and coronal (C) contrast-enhanced CT in a 67-year-old woman with marked antral narrowing (arrows) due to antral linitis plastica from gastric adenocarcinoma.
A
B
C
Figure 2-62. Barium swallow, axial contrast-enhanced CT, and PET in a 66-year-old woman with a cardial tumor extending into the lower esophagus (A; arrowhead) and metastatic lymph nodes (B; arrows) with uptake on PET (C; arrows).
A B C
Figure 2-61. Axial contrast-enhanced CT (A and B) and PET (C) in a 62-year-old man with mural thickening of the gastric body (large arrows) due to adenocarcinoma, which demonstrates marked FDG uptake (small arrow).
B
A
A
Figure 2-64. UGI series (A) and axial contrast-enhanced CT (B) in a 72-year-old woman with fixed narrowing of the gastric body and antrum (linitis
plastica appearance) (arrows) due to gastric adenocarcinoma.
Figure 2-65. UGI series in a 66-year-old woman with a linitis plastica– appearing stomach due to scirrhous gastric carcinoma.
Figure 2-66. Axial contrast-enhanced CT in a 70-year-old man with
infiltrative mass of the gastric body (large arrow) that has spread beyond the confines of the gastric wall (small arrow).
A
B
Figure 2-67. Coronal and axial-contrast enhanced CT in a 51-year-old woman with an antral gastric carcinoma (A; large arrow) and bilateral adnexal masses (B; small arrows) due to Krukenberg metastases.
cake (arrow).
B
A
Figure 2-70. A, Axial and coronal contrast-enhanced CT in a 30-year-old woman with a malignant gastric GIST (large arrow). B, A large part of the mass
(small arrow) is exophytic to the stomach. There are perigastric metastatic lymph nodes (arrowhead).
A
A
B
S
tomach63
the more common adenocarcinoma. MALT lymphoma most com- monly affects the stomach and represents a low-grade B-cell lym- phoma. Because of its low grade, it can be difficult to detect with either CT or PET. It is heavily associated with H. pylori, which is thought to be causative as a result of the chronic inflammatory reaction induced in the infected stomach. Treatment and eradica- tion of gastric H. pylori are often curative.
At imaging, there are various presentations of gastric lym- phoma, including a large ulcerating lesion, multiple polypoid lesions (with or without ulceration), or an infiltrating mass that can result in a linitis plastica appearance (Figs. 2-72, 2-73, and 2-74). These features can usually be observed on CT, but dif- ferentiation from other malignant diagnoses is sometimes diffi- cult because of similar appearance on imaging. CT will readily demonstrate extragastric extension or remote adenopathy and hepatosplenomegaly.
Posttransplant lymphoproliferative disorder (PTLD) occurs as a complication after prolonged immunosuppression, mostly among transplant recipients. It is due to an uncontrolled prolif- eration of B cells infected with Epstein-Barr virus (EBV) and the disease; therefore it has similarities with Burkitt lymphoma. The disease can respond to the cessation of the immunosuppressive therapy, although some patients progress to typical non-Hodg- kin B-cell lymphoma. Extranodal involvement is much more common than nodal involvement and affects the GI tract most commonly, typically the small bowel, then the colon, stomach, duodenum, and esophagus in descending frequency. Most other abdominal organs can also be involved, including the lung and central nervous system. Implanted allografts can also succumb to disease (e.g., liver, renal, heart/lung).
Imaging features in the bowel are similar to other GI lym- phoma, including circumferential wall thickening (sometimes marked) and aneurysmal luminal dilatation. Characteristically, the disease ulcerates and then perforates far more frequently than other types of lymphoma.