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Solid Omental Tumors Workup

  • Author: Kendrix J Evans, MD, MS; Chief Editor: John Geibel, MD, DSc, MSc, MA  more...
 
Updated: Aug 10, 2015
 

Laboratory Studies

Standard preoperative laboratory studies include the following:

  • Coagulation evaluation
  • Complete blood count (CBC)
  • Electrolytes
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Imaging Studies

Ultrasonography

Most patients undergo abdominal ultrasonography as a first-line screening imaging study. This modality can indicate the presence of a mass in the midabdomen and can differentiate cystic tumors from solid tumors; however, it usually cannot identify the primary site of the tumor and its characteristics. Consequently, computed tomography (CT) of the abdomen is the study of choice in helping to diagnose omental tumors.

Computed tomography

CT provides anatomic details and usually identify the primary tumor site. It may also demonstrate displacement or compression on adjacent organs. In a review of primary omental leiomyosarcomas, all three cases revealed CT findings of a flat, pancakelike mass with multiple cystic spaces with enhancement of the solid areas of the masses.[25] The masses were located in the anterior compartment of the abdomen, usually anterior to the small bowel loops and transverse colon. This differs from the appearance of omental metastatic disease on CT, which has been described as an "omental cake" owing to the thickened tumor-implanted omentum floating in ascites.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) is another available modality that can aid in differentiating cystic tumors from solid tumors. MRI is not operator dependent and requires no preparation contrast medium; however, it is more time-consuming and expensive than other imaging modalities.

Positron emission tomography

When a gastrointestinal (GI) stromal tumor (GIST) is suspected, imaging with 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (FDG-PET) can complement contrast CT in helping to differentiate benign tissue from malignant tissue and necrotic scar from active tumor. Baseline PET is recommended before initiation of treatment with imatinib because 80% of patients will exhibit response based on PET images.

Angiography

Angiography can be helpful in patients with a suspected omental tumor. The major arterial blood supply of the greater omentum is largely from the right and left gastroepiploic arteries, which are derived from the gastroduodenal and splenic arteries. Knowledge of these vascular structures helps in diagnosing an omental tumor. Malignant tumors are favored when angiography demonstrates a hypervascular mass with neovascularity. Angiography should be performed to determine the feeding artery of the tumor as well as its vascularity.

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Biopsy

Preoperative fine-needle aspiration (FNA) and core-needle biopsies are controversial. Although some surgeons find these procedures to be helpful in confirming the diagnosis of these abdominal masses, others argue that the risk of potentially contaminating the abdominal cavity with tumor cells is increased.

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Histologic Findings

Primary omental tumors with the following histologic types have been reported:

  • Leiomyosarcoma
  • Fibrosarcoma
  • Hemangiopericytoma
  • Schwannoma
  • Spindle cell sarcoma
  • Liposarcoma [26, 27]
  • Leiomyoma
  • Lipoma
  • Fibroma
  • Mesothelioma
  • Cysts
  • Lipoblastoma
  • Leiomyoblastoma [14]

Liposarcomas are further classified into the following four different subtypes[26, 27] :

  • Myxoid
  • Round cell
  • Well differentiated
  • Pleomorphic

The difference between benign and malignant omental tumors depends on the evaluation of many parameters (eg, size, pleomorphism, mitotic activity, necrosis, metastasis). Benign and malignant lesions are almost equally distributed.

Omental GISTs have positive staining for CD 117 (c-kit proto-oncogene protein product), which are present in the interstitial cells of Cajal (ICCs). ICCs are the pacemaker cells that are important for GI tract motility. Omental GISTs also are positive for vimentin during immunohistochemical staining. Vimentin is a protein found in cells of mesenchymal origin.

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Contributor Information and Disclosures
Author

Kendrix J Evans, MD, MS Resident Physician, Department of General Surgery, University of Utah School of Medicine

Kendrix J Evans, MD, MS is a member of the following medical societies: American College of Surgeons, American Medical Association, American Medical Student Association/Foundation, Association of Military Surgeons of the US, Christian Medical and Dental Associations

Disclosure: Nothing to disclose.

Coauthor(s)

A Letch Kline, MD Chief, Academic Affliations, Gulf Coast Veterans Health Care System; Clinical Assistant Professor, Department of Surgery, Uniformed Services University of the Health Sciences, F Edward Hebert School of Medicine

A Letch Kline, MD is a member of the following medical societies: American College of Chest Physicians, American College of Surgeons, Southeastern Surgical Congress

Disclosure: Nothing to disclose.

Quintessa Miller, MD 

Quintessa Miller, MD is a member of the following medical societies: American College of Surgeons, National Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

David L Morris, MD, PhD, FRACS Professor, Department of Surgery, St George Hospital, University of New South Wales, Australia

David L Morris, MD, PhD, FRACS is a member of the following medical societies: British Society of Gastroenterology

Disclosure: Received none from RFA Medical for director; Received none from MRC Biotec for director.

Chief Editor

John Geibel, MD, DSc, MSc, MA Vice Chair and Professor, Department of Surgery, Section of Gastrointestinal Medicine, and Department of Cellular and Molecular Physiology, Yale University School of Medicine; Director, Surgical Research, Department of Surgery, Yale-New Haven Hospital; American Gastroenterological Association Fellow

John Geibel, MD, DSc, MSc, MA is a member of the following medical societies: American Gastroenterological Association, American Physiological Society, American Society of Nephrology, Association for Academic Surgery, International Society of Nephrology, New York Academy of Sciences, Society for Surgery of the Alimentary Tract

Disclosure: Received royalty from AMGEN for consulting; Received ownership interest from Ardelyx for consulting.

Additional Contributors

Juan B Ochoa, MD Assistant Professor, Department of Surgery, University of Pittsburgh School of Medicine; Medical and Scientific Director, HCN, Nestle Healthcare Nutrition

Disclosure: Nothing to disclose.

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Diagram of subdivisions of the omentum. The greater omentum is attached to the caudal border of the greater curvature of the stomach and consists of the hepatoduodenal, gastrocolic, and gastrosplenic ligaments. The lesser omentum is divisible into 2 parts: the hepatogastric ligament and the hepatoduodenal ligament.
The anterior double-layered fold of the greater omentum descends from the stomach and the first part of the duodenum in front of the small intestine and ascends behind itself as far as the transverse colon.
Table 1. Distribution of Primary Omental Tumors
Tumor Histology Number of Cases % of Total
Leiomyosarcoma 22 17
Hemangiopericytoma 8 6
Sarcoma 3 2
Myosarcoma 2 1.5
Fibrosarcoma 3 2
Reticulosarcoma 1 1
Spindle cell sarcoma 1 1
Liposarcoma 1 1
Rhabdomyosarcoma 1 1
Leiomyoma/leiomyoblastoma 14 11
Lipoma 5 4
Fibroma 3 2
Fibromatosis 2 1.5
Mesothelioma 2 1.5
Endothelioma 1 1
Myxoma 1 1
Neurofibroma 1 1
Malignant fibrous histiocytoma 1 1
Gastrointestinal stromal tumor 21 16
Glomus 2 1.5
Teratoma 28 21
Lipoblastoma 8 6
Total 131 100
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