Malignant tumours of the small intestine: a review of histopathology, multidetector CT and MRI aspects

Abstract

Small bowel neoplasms, including adenocarcinoma, carcinoid tumour, lymphoma and gastrointestinal stromal tumours, represent a small percentage of gastrointestinal cancers, yet are among those with the poorest prognosis compared with other gastrointestinal malignancies. Unclear clinical scenarios and difficult radiological diagnosis often delay treatment with negative effects on patient survival. Recently, multidetector CT (MDCT) and MRI have been introduced as feasible and accurate diagnostic techniques for the identification and staging of small bowel neoplasms. These techniques are gradually replacing conventional barium radiography as the tool of choice. However, the inherent technical and physiological challenges of small bowel imaging require a familiarity with patient preparation and scan protocols. Adequate knowledge of the histopathology and natural evolution of small bowel neoplasms is also important for differential diagnosis. The aim of this article is to review MDCT and MRI protocols for the evaluation of small bowel tumours and to provide a concise yet comprehensive guide to the most relevant imaging features relative to histopathology.

Figure 1

Different oral contrast agents for multidetector CT of the small intestine (SI). (a) Tap water is an easy and inexpensive way to distend the SI. Water is frequently used to better visualise the superior portion of GI tract (stomach and duodenum); however, it is rapidly absorbed during its passage through the jejunum and ileum with a progressive loss of bowel distension in the distal tract. (b) High-concentration opaque oral contrast agents present a low absorption rate and remain in the bowel for a long time; however, their high attenuation characteristics may not allow an accurate evaluation of the intestinal lumen or enhancement of the bowel walls. (c) Low-concentration oral contrast agents provide excellent distension of the bowel lumen owing to moderate osmotic pressure, maintaining at the same time an adequate attenuation gradient between wall and lumen.

Figure 2

Different oral contrast agents in MRI of the small intestine (SI). Double-negative contrast agents produce low-signal intensity of bowel lumen on both (a) T₁ and (b) T₂ weighted sequences. With these contrast agents the visualisation of the bowel's wall (w) is preferred to that of the lumen (l), emphasising the identification of parietal and extra-parietal findings such as oedema or fat stranding. With the use of positive contrast agents, the visualisation of bowel lumen is privileged on both (c) T₁ and (d) T₂ weighted sequences; the most significant limitation is represented by the fact that wall enhancement after intravenous Gd administration can be masked by the higher lumen signal on T₁ weighted sequences. Biphasic contrast agents produce an optimal contrast between lumen and walls on both (e) T₂ weighted (bright lumen and dark walls) and (f) T₁ weighted sequences (dark lumen and bright walls).

Figure 3

Adenocarcinoma. (a) Photograph of resected and opened duodenum from a 67-year-old man who presented with melaena shows a 2.0 cm vegetating lesion originating from the mucosa surrounding the duodenal papilla. (b) Low-power photomicrograph (magnification ×4; haematoxylin–eosin stain) of the lesion shows neoplastic infiltration (asterisk) of the mucosal epithelium and muscularis propria.

Figure 4

Adenocarcinoma. Same patient as Figure 3. (a) Magnetic resonance cholangiopancreatography (MRCP) demonstrates obstruction of the main pancreatic duct and common bile duct with signal loss at the duodenal papilla (arrow), stasis and dilatation of the hepatic biliary branches. (b) Fat-suppressed axial T₁ spoiled gradient-echo (SPGRE) sequences obtained after intravenous administration of contrast agent and water distension of the duodenum allowed identification of a hypervascular protrusion from the papilla (asterisk). (c) Multidetector CT performed after biliary stenting confirm the presence of the lesion (asterisk) that can be clearly differentiated from the pancreatic parenchyma, excluding, at the same time, infiltration of the perivisceral fat tissue.

Figure 5

Adenocarcinoma. 49-year-old male with melaena and endoscopic diagnosis of duodenal mass. The high intraluminal signal achieved on (a) MR true fast imaging with steady-state precession (true-FISP) image after water distension of the duodenum allows the identification of a polypoid lesion (arrow) with a thick stalk and lobulated profiles facing the duodenal papilla. The contour of the outer wall layers is preserved, excluding deep extraluminal infiltration. (b) In this case, the poor attenuation gradient and lesser lumen distension attained on multidetector CT prevent a precise delineation of the lesion (arrow).

Figure 6

Adenocarcinoma. 89-year-old male with weight loss, abdominal pain and melaena admitted to the emergency room. Multidetector CT images obtained after oral administration of a low-concentration contrast agent demonstrate an eccentric and partially stenosing wall thickening involving one of the proximal jejunal loops (arrows). The lesion extends beyond the wall infiltrating the perivisceral fat. Multiple peritoneal implants (arrowheads), perihepatic ascites (black arrow) and some centimetric lymphadenopaties (asterisk) are also visualised.

Figure 7

Adenocarcinoma. 66-year-old male with weight loss, melaena and incomplete colonoscopy. Multidetector CT images demonstrate a large mass originating from the last ileal loop ((a) arrows) infiltrating the ileocaecal valve. The lesion extends into the perivisceral fat and infiltrates the peritoneum ((b) arrowheads). A small liver metastasis ((b) asterisk) and necrotic lymphadenopaties ((c) asterisk) can also be identified.

Figure 8

Carcinoid tumour. (a) Photograph of resected and opened jejunal loop (on the right) and mesentery (on the left) from a 57-year-old woman who presented with diarrhoea, flushing and abdominal pain shows a 1.5 cm rounded lesion originating from the jejunal wall without mucosal effacement and stranding of the mesentery ending in a plaque-like area of desmoplastic reaction. (b) Low-power photomicrograph (magnification ×4; haematoxylin–eosin stain) of the lesion shows neoplastic involvement of the submucosal layer extensively with transmural extension (arrows). There is no neoplastic change of surface epithelium. (c) Cromogranin antibodies stain confirms the diagnosis of carcinoid tumour (asterisk).

Figure 9

Carcinoid tumour. Same patient as Figure 8. (a) Coronal true fast imaging with steady-state precession (true-FISP) image demonstrates a small filling defect (arrow) in the first jejunal loop; some liver lesions can also be visualised. (b) Multidetector CT image obtained in the same patient in the arterial phase show a small intraluminal enhancing lesion (arrow) and mass forming desmoplastic alteration of the mesentery (arrowhead) with punctate calcifications (asterisk). (c) The portal-venous scan also shows multiple hypervascular liver metastases (asterisk).

Figure 10

Carcinoid tumour. 50-year-old male with multiple liver lesions identified at a routine ultrasound scan from an unknown primary cancer. (a) Multidetector CT images obtained in the portal-venous phase demonstrate an enhancing ileal lesion (arrow) with mass forming desmoplastic reaction in the mesentery (asterisk) the prominent mesenteric involvement is well visualised on the axial images ((b) arrowheads).

Figure 11

Atypical carcinoid tumour. 46-year-old female with chronic diarrhoea, flushing, cardiac arrhythmia and high levels of urinary 5-HIAA. (a) Multidetector CT images demonstrate a circumferential thickening of the last ileal loop with sparing of the outer wall layers, (b) some mucosal irregularities can be identified on the retrograde view from virtual endoscopic reconstruction. (c) Caudal sections show marked fluid distension of ileal and jejunal loops owing to carcinoid-induced secretory discharge.

Figure 12

Non-Hodgkin B-cell lymphoma. (a) Photograph of resected ileal loops and mesentery from a 53-year-old man who presented with abdominal pain and small bowel occlusion shows a bulky, necrotic lymphadenopaty (arrow) and extensive amorphous, neoplastic infiltration of ileal walls and mesentery (asterisk). (b) Low-power photomicrograph (magnification ×4; haematoxylin-eosin stain) demonstrate effacement of mucosa by lymphoid cell infiltrate (asterisk) and adjacent, normal intestinal mucosa. (c) High-power photomicrograph (magnification ×400; haematoxylin–eosin stain) demonstrate large B cells infiltrating glandular crypts.

Figure 13

Lymphoma. 72-year-old female with previously treated non-Hodgkin B-cell lymphoma. (a) Axial T₂ weighted turbo spin echo image demonstrate diffuse wall thickening of one of the last ileal loops (arrow). Signal alteration of the bone marrow of the right iliac wing is also identified (asterisk). (b) T₁ weighted images without and (c) with fat-saturation confirm the findings (arrows), allowing the exclusion of extramural disease. The presence of bone marrow infiltration is well delineated (asterisk) along with a diffuse periosteal enhancement after gadolinium administration.

Figure 14

Lymphoma. Same patient as Figure 12. Multidetector CT images demonstrate a circumferential thickening of (a) the proximal jejunum with mucosal irregularity (arrow) and sparing of the outer wall layers ((b) arrow), bulky lymphadenopaties (asterisk) are identified along the mesenteric vessels.

Figure 15

Gastrointestinal stromal tumour (GIST). (a) Photograph of resected and opened exophytic mass originating from a jejunal loop (not shown) in a 79-year-old woman who presented with abdominal discomfort shows a well-defined inner core (asterisk) surrounded by a larger solid tissue with necrotic and haemorrhagic changes. (b) Low-power photomicrograph (magnification ×4; haematoxylin–eosin stain) of the inner core (asterisk) shows involvement of all submucosal layers without infiltration of the mucosal epithelium. (c) CD-117 antibodies stain confirms GIST diagnosis (asterisk).

Figure 16

Low-grade subserosal gastrointestinal stromal tumour (GIST). Same patient as Figure 15. (a) Multidetector CT images demonstrate a large lesion (arrow) with well-defined margins originating from the mesenteric side of one of the last ileal loops, perihepatic ascites is confirmed (black arrow). (b) Sagittal reconstruction clearly demonstrates the prevalent extraluminal extension of the lesion, also evidencing multiple necrotic foci inside the lesion (asterisk).

Figure 17

High-grade intraluminal gastrointestinal stromal tumour (GIST). 73-year-old female with previously resected GIST and recent onset of intestinal obstruction. (a) Coronal T₂ weighted half-fourier acquisition single shot turbo spin echo image demonstrate a concentric wall thickening at the site of the previous resection (arrow) with dilatation of the upper bowel loop (black arrow). Multiple intestinal and peritoneal implants ((b) asterisk) are also identified. (c) Fat-saturated T₁ weighted spoiled gradient-echo image obtained after intravenous gadolinium administration show hypervascular liver lesions (arrowheads) and pelvic peritoneal implants ((d) asterisk).

Figure 18

Metastases. (a) Photograph of resected ileal loops and exophitic masses originating from the bowel wall in a 68-year-old woman with a previous diagnosis of cutaneous melanoma who presented with small bowel occlusion. (b) Low-power photomicrograph (magnification ×4; haematoxylin–eosin stain) shows neoplastic infiltration of the outer layers of bowel wall (asterisk) with intact mucosal epithelium (arrowhead). (c) High-power photomicrograph (magnification ×400; haematoxylin–eosin stain) demonstrate proliferation of round anaplastic cells involving the muscularis propria (arrows).

Figure 19

Metastases (melanoma). Same patient as Figure 18. (a) Multidetector CT images demonstrate a large lesion (arrow), with ill-defined lobulated margins, developing from inner wall layers of an ileal loop, while the lesion develops as a large mass with a necrotic core ((b, c) arrowheads) the bowel is not obstructed for the predominant extramural, vegetating aspect of the tumour.