Beyond the GIST: mesenchymal tumors of the stomach

Abstract

Intramural gastric masses arise in the wall of the stomach (generally within the submucosa or muscularis propria), often with intact overlying mucosa. These tumors are typically mesenchymal in origin and have overlapping radiologic appearances. A combination of features such as location, attenuation, enhancement, and growth pattern may suggest one diagnosis over another. Gastrointestinal stromal tumors (GISTs) account for the majority of intramural tumors and can vary widely in appearance, from small intraluminal lesions to exophytic masses that protrude into the peritoneal cavity, commonly with areas of hemorrhage or necrosis. A well-circumscribed mass measuring -70 to -120 HU is a lipoma. Leiomyomas usually manifest as low-attenuation masses at the gastric cardia. Homogeneous attenuation is a noteworthy characteristic of schwannomas, particularly for larger lesions that might otherwise be mistaken for GISTs. A hypervascular mass in the antrum is a common manifestation of glomus tumors. Hemangiomas are also hypervascular but often manifest in childhood. Inflammatory fibroid polyps usually arise as a polypoid mass in the antrum. Inflammatory myofibroblastic tumors are infiltrative neoplasms with a propensity for local recurrence. Plexiform fibromyxomas are rare, usually antral tumors. Carcinoid tumors are epithelial in origin, but often submucosal in location, and therefore should be distinguished from other intramural lesions. Multiple carcinoid tumors are associated with hypergastrinemia, either in the setting of chronic atrophic gastritis or Zollinger-Ellison syndrome. Sporadic solitary carcinoid tumors not associated with hypergastrinemia have a higher rate of metastasis. Histopathologic analysis, including immunohistochemistry, is usually required for diagnosis of intramural masses.

Figure 1a

Anatomy of the stomach. (a) Drawing illustrates the divisions of the stomach into the cardia, fundus, body, antrum, and pylorus. (b) Photomicrograph shows a diagrammed cross section of a gastric specimen. Similar to other parts of the gastrointestinal tract, the stomach has four layers: mucosa, submucosa, muscularis propria, and serosa.

Figure 1b

Anatomy of the stomach. (a) Drawing illustrates the divisions of the stomach into the cardia, fundus, body, antrum, and pylorus. (b) Photomicrograph shows a diagrammed cross section of a gastric specimen. Similar to other parts of the gastrointestinal tract, the stomach has four layers: mucosa, submucosa, muscularis propria, and serosa.

Figure 2a

Growth patterns of intramural masses. (a–c) Different growth patterns of GISTs (*) are illustrated on contrast material–enhanced computed tomographic (CT) images from three different cases: exophytic (a), dumbbell-shaped (b), and endoluminal (c). (Image a is from a 51-year-old woman; b, a 56-year-old man; and c, a 64-year-old woman.) (d) Endoscopic image in the same patient as in c shows the intramural lesion with smooth overlying mucosa and central umbilication. (e) Fluoroscopic image in an 81-year-old woman shows a smoothly marginated mass with a central ulcer (arrow), forming obtuse angles with the gastric wall. (f) Axial contrast-enhanced CT image in a 68-year-old man shows an exophytic GIST with focal ulceration (arrow).

Figure 2b

Growth patterns of intramural masses. (a–c) Different growth patterns of GISTs (*) are illustrated on contrast material–enhanced computed tomographic (CT) images from three different cases: exophytic (a), dumbbell-shaped (b), and endoluminal (c). (Image a is from a 51-year-old woman; b, a 56-year-old man; and c, a 64-year-old woman.) (d) Endoscopic image in the same patient as in c shows the intramural lesion with smooth overlying mucosa and central umbilication. (e) Fluoroscopic image in an 81-year-old woman shows a smoothly marginated mass with a central ulcer (arrow), forming obtuse angles with the gastric wall. (f) Axial contrast-enhanced CT image in a 68-year-old man shows an exophytic GIST with focal ulceration (arrow).

Figure 2c

Growth patterns of intramural masses. (a–c) Different growth patterns of GISTs (*) are illustrated on contrast material–enhanced computed tomographic (CT) images from three different cases: exophytic (a), dumbbell-shaped (b), and endoluminal (c). (Image a is from a 51-year-old woman; b, a 56-year-old man; and c, a 64-year-old woman.) (d) Endoscopic image in the same patient as in c shows the intramural lesion with smooth overlying mucosa and central umbilication. (e) Fluoroscopic image in an 81-year-old woman shows a smoothly marginated mass with a central ulcer (arrow), forming obtuse angles with the gastric wall. (f) Axial contrast-enhanced CT image in a 68-year-old man shows an exophytic GIST with focal ulceration (arrow).

Figure 2d

Growth patterns of intramural masses. (a–c) Different growth patterns of GISTs (*) are illustrated on contrast material–enhanced computed tomographic (CT) images from three different cases: exophytic (a), dumbbell-shaped (b), and endoluminal (c). (Image a is from a 51-year-old woman; b, a 56-year-old man; and c, a 64-year-old woman.) (d) Endoscopic image in the same patient as in c shows the intramural lesion with smooth overlying mucosa and central umbilication. (e) Fluoroscopic image in an 81-year-old woman shows a smoothly marginated mass with a central ulcer (arrow), forming obtuse angles with the gastric wall. (f) Axial contrast-enhanced CT image in a 68-year-old man shows an exophytic GIST with focal ulceration (arrow).

Figure 2e

Growth patterns of intramural masses. (a–c) Different growth patterns of GISTs (*) are illustrated on contrast material–enhanced computed tomographic (CT) images from three different cases: exophytic (a), dumbbell-shaped (b), and endoluminal (c). (Image a is from a 51-year-old woman; b, a 56-year-old man; and c, a 64-year-old woman.) (d) Endoscopic image in the same patient as in c shows the intramural lesion with smooth overlying mucosa and central umbilication. (e) Fluoroscopic image in an 81-year-old woman shows a smoothly marginated mass with a central ulcer (arrow), forming obtuse angles with the gastric wall. (f) Axial contrast-enhanced CT image in a 68-year-old man shows an exophytic GIST with focal ulceration (arrow).

Figure 2f

Growth patterns of intramural masses. (a–c) Different growth patterns of GISTs (*) are illustrated on contrast material–enhanced computed tomographic (CT) images from three different cases: exophytic (a), dumbbell-shaped (b), and endoluminal (c). (Image a is from a 51-year-old woman; b, a 56-year-old man; and c, a 64-year-old woman.) (d) Endoscopic image in the same patient as in c shows the intramural lesion with smooth overlying mucosa and central umbilication. (e) Fluoroscopic image in an 81-year-old woman shows a smoothly marginated mass with a central ulcer (arrow), forming obtuse angles with the gastric wall. (f) Axial contrast-enhanced CT image in a 68-year-old man shows an exophytic GIST with focal ulceration (arrow).

Figure 3a

Cavitary GIST in a 64-year-old man with abdominal pain, anemia, and a 20-lb (9-kg) weight loss. (a) Axial contrast-enhanced CT image shows an 11-cm cavitary exophytic tumor. (b) Follow-up contrast-enhanced CT image, obtained after 2 months of imatinib therapy, shows reduction in the size of the tumor, which now measures 6 cm.

Figure 3b

Cavitary GIST in a 64-year-old man with abdominal pain, anemia, and a 20-lb (9-kg) weight loss. (a) Axial contrast-enhanced CT image shows an 11-cm cavitary exophytic tumor. (b) Follow-up contrast-enhanced CT image, obtained after 2 months of imatinib therapy, shows reduction in the size of the tumor, which now measures 6 cm.

Figure 4a

GIST with high risk for progressive disease in a 38-year-old man who had undergone imatinib therapy. (a) Photograph of a gastrectomy specimen, obtained after imatinib therapy, shows a necrotic intramural tumor. Scale is in centimeters. (b) Photomicrograph (original magnification, ×400; hematoxylin-eosin stain) shows that the tumor is composed of spindle cells, which are arranged in intersecting fascicles. Mitotic figures (circles), an indicator of high risk of progression, are easily identified. (c) Photomicrograph (original magnification, ×40; immunohistochemical stain for c-KIT) demonstrates brown staining of the cytoplasm, which confirms that the neoplastic cells are diffusely and strongly immunoreactive for c-KIT.

Figure 4b

GIST with high risk for progressive disease in a 38-year-old man who had undergone imatinib therapy. (a) Photograph of a gastrectomy specimen, obtained after imatinib therapy, shows a necrotic intramural tumor. Scale is in centimeters. (b) Photomicrograph (original magnification, ×400; hematoxylin-eosin stain) shows that the tumor is composed of spindle cells, which are arranged in intersecting fascicles. Mitotic figures (circles), an indicator of high risk of progression, are easily identified. (c) Photomicrograph (original magnification, ×40; immunohistochemical stain for c-KIT) demonstrates brown staining of the cytoplasm, which confirms that the neoplastic cells are diffusely and strongly immunoreactive for c-KIT.

Figure 4c

GIST with high risk for progressive disease in a 38-year-old man who had undergone imatinib therapy. (a) Photograph of a gastrectomy specimen, obtained after imatinib therapy, shows a necrotic intramural tumor. Scale is in centimeters. (b) Photomicrograph (original magnification, ×400; hematoxylin-eosin stain) shows that the tumor is composed of spindle cells, which are arranged in intersecting fascicles. Mitotic figures (circles), an indicator of high risk of progression, are easily identified. (c) Photomicrograph (original magnification, ×40; immunohistochemical stain for c-KIT) demonstrates brown staining of the cytoplasm, which confirms that the neoplastic cells are diffusely and strongly immunoreactive for c-KIT.

Figure 5a

Examples of non-GIST sarcomas. (a) Axial contrast-enhanced CT image in a 62-year-old man demonstrates a dedifferentiated liposarcoma (*) involving the stomach. (b) Coronal contrast-enhanced CT image in a 64-year-old man reveals a tumor (*) for which histologic analysis revealed high-grade spindle cell sarcoma, findings suggestive of leiomyosarcoma.

Figure 5b

Examples of non-GIST sarcomas. (a) Axial contrast-enhanced CT image in a 62-year-old man demonstrates a dedifferentiated liposarcoma (*) involving the stomach. (b) Coronal contrast-enhanced CT image in a 64-year-old man reveals a tumor (*) for which histologic analysis revealed high-grade spindle cell sarcoma, findings suggestive of leiomyosarcoma.

Figure 6a

Gastric lipoma. (a) Photograph of a gastrectomy specimen shows a well-circumscribed tumor with a homogeneous, pale-yellow cut surface. (b) Axial contrast-enhanced CT image from a different case shows an endoluminal lesion with uniform fat attenuation (arrow), a finding diagnostic of a lipoma.

Figure 6b

Gastric lipoma. (a) Photograph of a gastrectomy specimen shows a well-circumscribed tumor with a homogeneous, pale-yellow cut surface. (b) Axial contrast-enhanced CT image from a different case shows an endoluminal lesion with uniform fat attenuation (arrow), a finding diagnostic of a lipoma.

Figure 7a

Gastric leiomyoma in a 36-year-old woman. (a) Axial contrast-enhanced CT image shows a leiomyoma (arrow) in the gastric cardia, with intact enhancing mucosa. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows the well-circumscribed tumor, which originated in the muscularis propria, abutting but not invading the overlying submucosa.

Figure 7b

Gastric leiomyoma in a 36-year-old woman. (a) Axial contrast-enhanced CT image shows a leiomyoma (arrow) in the gastric cardia, with intact enhancing mucosa. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows the well-circumscribed tumor, which originated in the muscularis propria, abutting but not invading the overlying submucosa.

Figure 8a

Gastric schwannomas. (a) Axial contrast-enhanced CT image in a 69-year-old woman demonstrates a schwannoma (arrow), incidentally discovered during work-up of a GIST. (b) Endoscopic image in the same patient shows that the mass has smooth, overlying mucosa. (c, d) Axial contrast-enhanced CT images obtained at two levels show a 17-cm schwannoma (*) in a 35-year-old woman with a history of abdominal discomfort for several years. Note the relative homogeneity of the tumor, which would be unusual for a GIST of this size.

Figure 8b

Gastric schwannomas. (a) Axial contrast-enhanced CT image in a 69-year-old woman demonstrates a schwannoma (arrow), incidentally discovered during work-up of a GIST. (b) Endoscopic image in the same patient shows that the mass has smooth, overlying mucosa. (c, d) Axial contrast-enhanced CT images obtained at two levels show a 17-cm schwannoma (*) in a 35-year-old woman with a history of abdominal discomfort for several years. Note the relative homogeneity of the tumor, which would be unusual for a GIST of this size.

Figure 8c

Gastric schwannomas. (a) Axial contrast-enhanced CT image in a 69-year-old woman demonstrates a schwannoma (arrow), incidentally discovered during work-up of a GIST. (b) Endoscopic image in the same patient shows that the mass has smooth, overlying mucosa. (c, d) Axial contrast-enhanced CT images obtained at two levels show a 17-cm schwannoma (*) in a 35-year-old woman with a history of abdominal discomfort for several years. Note the relative homogeneity of the tumor, which would be unusual for a GIST of this size.

Figure 8d

Gastric schwannomas. (a) Axial contrast-enhanced CT image in a 69-year-old woman demonstrates a schwannoma (arrow), incidentally discovered during work-up of a GIST. (b) Endoscopic image in the same patient shows that the mass has smooth, overlying mucosa. (c, d) Axial contrast-enhanced CT images obtained at two levels show a 17-cm schwannoma (*) in a 35-year-old woman with a history of abdominal discomfort for several years. Note the relative homogeneity of the tumor, which would be unusual for a GIST of this size.

Figure 9a

Histopathologic features of schwannoma (specimens from a 36-year-old woman). (a) Photograph of a gastrectomy specimen shows a slightly lobulated, but well-circumscribed, homogeneous intramural tumor. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows that the tumor retains its circumscription and pushes into the submucosa. The tumor is cuffed by lymphoid aggregates (arrowheads), a characteristic feature of schwannomas in this location.

Figure 9b

Histopathologic features of schwannoma (specimens from a 36-year-old woman). (a) Photograph of a gastrectomy specimen shows a slightly lobulated, but well-circumscribed, homogeneous intramural tumor. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows that the tumor retains its circumscription and pushes into the submucosa. The tumor is cuffed by lymphoid aggregates (arrowheads), a characteristic feature of schwannomas in this location.

Figure 10a

Glomus tumor incidentally found during work-up for fever in a 44-year-old woman. (a, b) Axial contrast-enhanced CT images obtained during the arterial (a) and delayed (b) phases demonstrate an arterially enhancing mass (arrow in a) in the gastric antrum with persistent enhancement (arrow in b). Note the preserved overlying mucosa in both phases. (c) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows the hypervascular tumor originating in the muscularis propria (* denotes vascular spaces).

Figure 10b

Glomus tumor incidentally found during work-up for fever in a 44-year-old woman. (a, b) Axial contrast-enhanced CT images obtained during the arterial (a) and delayed (b) phases demonstrate an arterially enhancing mass (arrow in a) in the gastric antrum with persistent enhancement (arrow in b). Note the preserved overlying mucosa in both phases. (c) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows the hypervascular tumor originating in the muscularis propria (* denotes vascular spaces).

Figure 10c

Glomus tumor incidentally found during work-up for fever in a 44-year-old woman. (a, b) Axial contrast-enhanced CT images obtained during the arterial (a) and delayed (b) phases demonstrate an arterially enhancing mass (arrow in a) in the gastric antrum with persistent enhancement (arrow in b). Note the preserved overlying mucosa in both phases. (c) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows the hypervascular tumor originating in the muscularis propria (* denotes vascular spaces).

Figure 11

Hemangioma. Axial contrast-enhanced CT image shows an avidly enhancing hemangioma (arrow) in the gastric antrum.

Figure 12a

Incidentally discovered IFP in a 53-year-old woman with a history of thyroid carcinoma. (a) Axial contrast-enhanced CT image demonstrates an enhancing mass (arrow) in the gastric body. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows that the tumor arises in the submucosa but infiltrates into the mucosa (arrowheads), forming a polypoid lesion. The tumor is composed of bland spindle cells with an inflammatory component.

Figure 12b

Incidentally discovered IFP in a 53-year-old woman with a history of thyroid carcinoma. (a) Axial contrast-enhanced CT image demonstrates an enhancing mass (arrow) in the gastric body. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) shows that the tumor arises in the submucosa but infiltrates into the mucosa (arrowheads), forming a polypoid lesion. The tumor is composed of bland spindle cells with an inflammatory component.

Figure 13

IMFT (pleomorphic variant) in a 69-year-old woman with fever, night sweats, and coagulopathy. Axial contrast-enhanced CT image shows an intramural, heterogeneously enhancing tumor (*) with endoluminal and exophytic growth.

Figure 14a

Plexiform fibromyxoma in a 31-year-old man with Peutz-Jeghers syndrome who presented with abdominal pain and melena. (a) Axial T2-weighted magnetic resonance (MR) image shows a hyperintense mass (*) in the gastric antrum. (b) Axial fat-saturated T1-weighted image, obtained after administration of gadolinium contrast material, shows that the mass (*) is avidly enhancing. The mass demonstrated fluid attenuation on CT images (not shown), a finding consistent with myxoid composition.

Figure 14b

Plexiform fibromyxoma in a 31-year-old man with Peutz-Jeghers syndrome who presented with abdominal pain and melena. (a) Axial T2-weighted magnetic resonance (MR) image shows a hyperintense mass (*) in the gastric antrum. (b) Axial fat-saturated T1-weighted image, obtained after administration of gadolinium contrast material, shows that the mass (*) is avidly enhancing. The mass demonstrated fluid attenuation on CT images (not shown), a finding consistent with myxoid composition.

Figure 15a

Type 1 gastric carcinoid. (a, b) Precontrast (a) and postcontrast (b) axial CT images, obtained in a 53-year-old woman with a 3-month history of abdominal pain, weight loss, and elevated levels of serum gastrin and chromogranin A, show an avidly enhancing mass (arrow) in the gastric body, with central ulceration. The mass was an unusual, solitary type 1 carcinoid arising in a background of atrophic gastritis. (c) CT image fused with scintigraphy performed after injection of indium 111 pentetreotide (Octreoscan) demonstrates avid radiotracer uptake in the gastric mass (arrow), characteristic of carcinoid tumor. The patient (same as in a and b) remained without evidence of disease 15 months after surgery, without further treatment. (d) Axial contrast-enhanced CT image from a different case shows a more typical example of type 1 gastric carcinoid, with multiple enhancing polypoid lesions (arrowheads).

Figure 15b

Type 1 gastric carcinoid. (a, b) Precontrast (a) and postcontrast (b) axial CT images, obtained in a 53-year-old woman with a 3-month history of abdominal pain, weight loss, and elevated levels of serum gastrin and chromogranin A, show an avidly enhancing mass (arrow) in the gastric body, with central ulceration. The mass was an unusual, solitary type 1 carcinoid arising in a background of atrophic gastritis. (c) CT image fused with scintigraphy performed after injection of indium 111 pentetreotide (Octreoscan) demonstrates avid radiotracer uptake in the gastric mass (arrow), characteristic of carcinoid tumor. The patient (same as in a and b) remained without evidence of disease 15 months after surgery, without further treatment. (d) Axial contrast-enhanced CT image from a different case shows a more typical example of type 1 gastric carcinoid, with multiple enhancing polypoid lesions (arrowheads).

Figure 15c

Type 1 gastric carcinoid. (a, b) Precontrast (a) and postcontrast (b) axial CT images, obtained in a 53-year-old woman with a 3-month history of abdominal pain, weight loss, and elevated levels of serum gastrin and chromogranin A, show an avidly enhancing mass (arrow) in the gastric body, with central ulceration. The mass was an unusual, solitary type 1 carcinoid arising in a background of atrophic gastritis. (c) CT image fused with scintigraphy performed after injection of indium 111 pentetreotide (Octreoscan) demonstrates avid radiotracer uptake in the gastric mass (arrow), characteristic of carcinoid tumor. The patient (same as in a and b) remained without evidence of disease 15 months after surgery, without further treatment. (d) Axial contrast-enhanced CT image from a different case shows a more typical example of type 1 gastric carcinoid, with multiple enhancing polypoid lesions (arrowheads).

Figure 15d

Type 1 gastric carcinoid. (a, b) Precontrast (a) and postcontrast (b) axial CT images, obtained in a 53-year-old woman with a 3-month history of abdominal pain, weight loss, and elevated levels of serum gastrin and chromogranin A, show an avidly enhancing mass (arrow) in the gastric body, with central ulceration. The mass was an unusual, solitary type 1 carcinoid arising in a background of atrophic gastritis. (c) CT image fused with scintigraphy performed after injection of indium 111 pentetreotide (Octreoscan) demonstrates avid radiotracer uptake in the gastric mass (arrow), characteristic of carcinoid tumor. The patient (same as in a and b) remained without evidence of disease 15 months after surgery, without further treatment. (d) Axial contrast-enhanced CT image from a different case shows a more typical example of type 1 gastric carcinoid, with multiple enhancing polypoid lesions (arrowheads).

Figure 16a

Type 1 gastric carcinoid tumor arising in a background of autoimmune metaplastic atrophic gastritis (same case as in Fig 15a–15c). (a) Photograph of a partial gastrectomy specimen shows an ovoid mass deep to the mucosa (arrow), with a heterogeneous cut surface. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) demonstrates a hypercellular tumor intermixed with hyalinized stroma. The bulk of the tumor is deep to the mucosa, which is atrophic and inflamed. (c) High-power photomicrograph (original magnification, ×200; hematoxylin-eosin stain) shows that the tumor is composed of round bland cells arranged in an insular growth pattern with intervening hyalinized stroma that contains small vessels. (d) Low-power photomicrograph (original magnification, ×40; immunohistochemical stain for synaptophysin) shows brown staining of cytoplasm, a finding indicative of diffuse positivity for synaptophysin.

Figure 16b

Type 1 gastric carcinoid tumor arising in a background of autoimmune metaplastic atrophic gastritis (same case as in Fig 15a–15c). (a) Photograph of a partial gastrectomy specimen shows an ovoid mass deep to the mucosa (arrow), with a heterogeneous cut surface. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) demonstrates a hypercellular tumor intermixed with hyalinized stroma. The bulk of the tumor is deep to the mucosa, which is atrophic and inflamed. (c) High-power photomicrograph (original magnification, ×200; hematoxylin-eosin stain) shows that the tumor is composed of round bland cells arranged in an insular growth pattern with intervening hyalinized stroma that contains small vessels. (d) Low-power photomicrograph (original magnification, ×40; immunohistochemical stain for synaptophysin) shows brown staining of cytoplasm, a finding indicative of diffuse positivity for synaptophysin.

Figure 16c

Type 1 gastric carcinoid tumor arising in a background of autoimmune metaplastic atrophic gastritis (same case as in Fig 15a–15c). (a) Photograph of a partial gastrectomy specimen shows an ovoid mass deep to the mucosa (arrow), with a heterogeneous cut surface. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) demonstrates a hypercellular tumor intermixed with hyalinized stroma. The bulk of the tumor is deep to the mucosa, which is atrophic and inflamed. (c) High-power photomicrograph (original magnification, ×200; hematoxylin-eosin stain) shows that the tumor is composed of round bland cells arranged in an insular growth pattern with intervening hyalinized stroma that contains small vessels. (d) Low-power photomicrograph (original magnification, ×40; immunohistochemical stain for synaptophysin) shows brown staining of cytoplasm, a finding indicative of diffuse positivity for synaptophysin.

Figure 16d

Type 1 gastric carcinoid tumor arising in a background of autoimmune metaplastic atrophic gastritis (same case as in Fig 15a–15c). (a) Photograph of a partial gastrectomy specimen shows an ovoid mass deep to the mucosa (arrow), with a heterogeneous cut surface. (b) Low-power photomicrograph (original magnification, ×20; hematoxylin-eosin stain) demonstrates a hypercellular tumor intermixed with hyalinized stroma. The bulk of the tumor is deep to the mucosa, which is atrophic and inflamed. (c) High-power photomicrograph (original magnification, ×200; hematoxylin-eosin stain) shows that the tumor is composed of round bland cells arranged in an insular growth pattern with intervening hyalinized stroma that contains small vessels. (d) Low-power photomicrograph (original magnification, ×40; immunohistochemical stain for synaptophysin) shows brown staining of cytoplasm, a finding indicative of diffuse positivity for synaptophysin.

Figure 17

Diagram summarizes an approach to the differential diagnosis of a solitary intramural gastric tumor.