Laboratory Studies
Unless obstruction or perforation occurs, low hemoglobin caused by acute or chronic bleeding may be the only laboratory evidence of leiomyosarcoma. If the bleeding is chronic, the appropriate indices will be affected.
Imaging Studies
Notably, as many as 40% of these tumors are discovered incidentally. With this in mind, the principle symptom or sign of leiomyosarcomas is gastrointestinal (GI) bleeding, sometimes massive.
Positive test results for occult blood in the stool of a patient demand a source. If colonoscopy and esophagogastroduodenoscopy (EGD) results are normal, always consider a focused contrast study of the small bowel followed by a computed tomography (CT) scan. In case the source of bleeding is not identified, consider CT enterography, magnetic resonance (MR) enterography or video-capsule endoscopy (VCE). Unfortunately, early detection of the tumor with CT scanning depends on the tumor size and may not be helpful.
In a study that evaluated 562 patients who underwent VCE from August 2001 to November 2003 for a variety of indications, 443 (79%) of the 562 had evidence of occult GI bleeding. [13] A diagnosis was made by VCE in 277 patients (49.3%). Of the 562 patients studied, 50 (8.9%) were found to have a small intestinal tumor, 48% of which were malignant. [13]
A single report describes the use of preoperative endoscopic ultrasonography in helping to plan resection. [9] Ludwig postulated that this modality might be useful; further study is necessary.
A study by Ping-Hong Zhou and colleagues that evaluated the use of miniprobe ultrasonography during colonoscopy in diagnosing submucosal tumors of the large intestine identified leiomyosarcoma as having inhomogeneous echoes and irregular borders.[ref10} Zhou et al also concluded that this technique provided information about the size and layer of origin of the tumors. As leiomyosarcoma account for only 0.1% of colonic malignancies, miniprobe ultrasonography is more useful in other submucosal tumors, such as lipomas and leiomyomas.
Procedures
Because leiomyosarcomas are intramural in origin and tend to grow extraluminally, biopsy tissue obtained from the luminal side from the lining over the tumor often will be reported as benign mucosa.
Computed Tomography (CT)-guided biopsy may be helpful in certain cases.
If possible, endoscopic ultrasonography with guided biopsy may be diagnostic. [14]
Histologic Findings
Leiomyosarcomas are malignant mesenchymal non-gastrointestinal stromal tumors (GISTs) with a high proliferation rate and positivity for desmin, alpha-MSA (alpha–muscle-specific actin), and vimentin. These tumors are spindle cell in character, with high cellularity. Leiomyomas arise from the smooth muscle cells in the muscularis propria or muscularis mucosa, can be intraluminal or extraluminal, and account for about 40% of benign intestinal neoplasms. Leiomyomas with more than 2 mitoses per high-power field are reclassified as leiomyosarcomas. The mitotic figure count is of supreme importance. A count of more than 5 mitotic figures per 10 high-powered fields places a tumor into the high-grade category. Necrosis often occurs with high-grade tumors. (See the images below.)
Colonic mucosa with gastrointestinal stromal tumor (GIST) involving the adjacent submucosa (hematoxylin and eosin [H&E] stain, medium power).
Clusters of tumor cells separated by a hyaline and mucin-rich stroma (hematoxylin and eosin [H&E] stain, medium power).
Oval- to spindle-shaped cells forming a fascicle (hematoxylin and eosin [H&E] stain, high power).
CD-34 stain showing a tumor (medium power). CD-34 is a myeloid progenitor cell antigen.
High-power magnification with CD-34 antigen immunohistochemical stain showing membrane positivity of the tumor cells.
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Colonic mucosa with gastrointestinal stromal tumor (GIST) involving the adjacent submucosa (hematoxylin and eosin [H&E] stain, medium power).
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Clusters of tumor cells separated by a hyaline and mucin-rich stroma (hematoxylin and eosin [H&E] stain, medium power).
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Oval- to spindle-shaped cells forming a fascicle (hematoxylin and eosin [H&E] stain, high power).
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CD-34 stain showing a tumor (medium power). CD-34 is a myeloid progenitor cell antigen.
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High-power magnification with CD-34 antigen immunohistochemical stain showing membrane positivity of the tumor cells.
