Medical Therapy
The rarity of primary omental tumors hinders adequate assessment of adjuvant therapy. Some reports have suggested that chemotherapy may be effective.
In the treatment of malignant hemangiopericytoma, several groups have observed that doxorubicin, either alone or in conjunction with other agents, can achieve response rates of up to 80%. [43] A 12-month course of adjuvant chemotherapy with doxorubicin, cytotoxin, and dimethyltriazenoimidazolecarboxamide (DTIC) has been suggested for the treatment of fibrosarcoma. In treating leiomyosarcoma, combination chemotherapy with hydroxyurea, etoposide, and dacarbazine has been used. Other agents used include intraperitoneal cisplatin with intravenous administration of ifosfamide and pirarubicin hydrochloride.
Radiation therapy (RT) has been reported to be effective for partially excised tumors or inoperable tumors. In one study, 50 Gy was used to treat a partially excised liposarcoma. The tumor recurred after several months, necessitating a further debulking operation. The benefits of RT must be weighed against the risk of injury to abdominal viscera, particularly the bowel.
For treatment of gastrointestinal (GI) stromal tumors (GISTs), which are refractory to standard chemotherapy, imatinib in conjunction with surgical resection has been advocated. [44, 45, 46] Imatinib acts by inhibiting tyrosine kinase enzymes. Several trials have been initiated to explore the role of imatinib as an adjuvant treatment for prolonging disease-free survival, as well as overall survival.
Recurrence is a concern after treatment with adjuvant imatinib. Risk factors for GIST recurrence include high tumor mitotic count, nongastric location, large size, rupture, and adjuvant imatinib for 12 months. [47]
Surgical Therapy
Indications and contraindications
Two main indications for surgery exist: diagnosis and treatment. One of the hallmarks of omental tumors is the inability of preoperative studies to identify specific pathologic entities. As noted (see Workup), preoperative fine-needle aspiration (FNA) biopsy (FNAB) and core needle biopsy (CNB) are controversial for diagnostic purposes in this setting.
With respect to therapy, complete surgical excision (total omentectomy) is the recommended treatment of primary omental tumors. Even when peritoneal implants are present, omentectomy appears to improve survival significantly. Solid omental tumors can also manifest rapidly because of bleeding or intestinal infarction, necessitating emergency surgery. Laparoscopic resection of a spontaneously ruptured primary extragastrointestinal stromal tumor of the greater omentum has been described. [48]
Absolute contraindications for surgical resection include inability to safely resect the tumor because of local invasion.
Complications
Most of the surgical procedures do not involve intestinal resections or resection of major organs. As a result, expected postoperative complications mirror those of other clean abdominal procedures. If intestinal resection is performed, the rate of infectious complications increases similarly to that of clean-contaminated procedures. Other possible complications include bleeding, pancreatitis, bowel obstruction, and intestinal ischemia.
Long-Term Monitoring
Recommendations for the follow-up care of patients with solid omental tumors have not been established. Because recurrences and metastases can occur more than 20 years after primary treatments for sarcomas, the authors recommend long-term follow-up care for these patients.
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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.
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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.
Tables
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 (GIST) |
21 |
16 |
Glomus tumor |
2 |
1.5 |
Teratoma |
28 |
21 |
Lipoblastoma |
8 |
6 |
Total |
131 |
100 |
