The Role of the Omentum in Oncomorphology
When ovarian neoplasms (ON) are suspected, the examination of biopsy or surgical material requires strict recording of a number of parameters. The greater omentum (greater omentum) plays a key role in the staging of the tumor process.
The pathological report must reflect the following data:
- Peritoneal spread: the presence of malignant cells in each individual peritoneal biopsy and directly within the greater omentum.
- Specific inclusions: the presence and nature of implants, foci of endosalpingiosis, as well as psammoma bodies in the biopsy specimens.
- Primary tumor characteristics: macroscopic dimensions, condition of the capsule (presence of damage or tumor invasion through the capsule).
- Microscopy: histological structure, presence of microinvasion or full-blown invasion, presence of unfavorable patterns (cribriform, micropapillary).
- Grade (Grade).
- Lymph nodes: exact indication of the total number of examined nodes and the number of involved lymph nodes.
- Treatment response: degree of therapeutic pathomorphosis (evaluated if the patient previously underwent chemotherapy).
Due to the rarity and high complexity of the morphological diagnosis of ON, clinical guidelines require a review of histological preparations (slides and blocks). This procedure ("second opinion") should be performed in a specialized oncological medical organization with experience in treating such patients. The main goal of the review is reliable confirmation of the morphological diagnosis.
Primary Omental Neoplasms
Primary tumors of the greater omentum are less common than secondary involvement, but they include both benign and malignant variants. In their morphological characteristics, they are completely analogous to neoplasms developing in the mesentery.
- Benign neoplasms: as a rule, they are well-circumscribed (well circumscribed) and localized strictly within the anatomical boundaries of the omentum.
- Malignant neoplasms: differ in indistinct margins (indistinct margins) and a pronounced tendency to infiltrate surrounding structures.
Diagnostic Radiology and Differential Diagnosis
Radiological diagnostics of omental pathologies is associated with a number of objective difficulties. The CT picture of malignant omental infiltration is visually similar to its secondary (metastatic) involvement.
Moreover, the malignant process on tomograms may be completely indistinguishable from:
- Inflammatory omental thickening (inflammatory thickening).
- Cystic omental disease.
- Omental fat necrosis.
Main interpretation rule: any CT findings regarding structural changes in the omentum lack absolute specificity. They must be evaluated by the physician strictly in the context of the specific patient's clinical presentation.
Related Pathologies of the Mesentery and Peritoneum
Since the omentum is closely connected to the peritoneum (peritoneum) and mesentery (mesentery), it is important to consider related pathological processes during diagnosis.
Mesenteric fibromatosis (Mesenteric Fibromatosis) On contrast-enhanced CT, it is visualized as a soft-tissue density mass in the mesentery. It is capable of causing segmental ischemia of the jejunum, which manifests as symmetrical thickening of its wall. In familial adenomatous polyposis, fibromatosis appears as a homogeneous mass with indistinct margins in the center of the small bowel mesentery and is accompanied by numerous polyps in the large intestine (e.g., in the sigmoid colon).
Liposarcomas (Liposarcomas) Much more commonly affect the retroperitoneum, but are also found in the mesentery and peritoneum. There are four histological types (in order of increasing malignancy grade): myxoid, well-differentiated, pleomorphic, and round cell.
The radiological picture is extremely variable and depends on the tissue composition. The density spectrum ranges from masses with a predominance of fatty, fluid, and soft-tissue components to tumors consisting exclusively of soft tissue. An important diagnostic criterion: in high-grade liposarcomas (pleomorphic and round cell), the presence of macroscopic adipose tissue is least likely.
Large mesenteric liposarcomas on contrast-enhanced CT contain areas of both fatty and soft-tissue density, and are characterized by encasement (encasing) of major peripheral vessels. On MRI (T1-weighted spin-echo), multiple fibrous strands, a hyperintense center (corresponding to the fatty element), and a hypointense periphery (corresponding to the undifferentiated sarcomatous element) are visualized in such tumors.
The golden rule of omental imaging: CT findings are nonspecific. Malignant infiltration, metastases, fat necrosis, and inflammatory thickening can look identical. The final conclusion is made only in conjunction with the clinical picture!
Class and exam questions
What greater omentum parameters must be reflected in the pathological report for ovarian tumors?
The report records the presence of malignant cells, as well as the presence and nature of implants, foci of endosalpingiosis, and psammoma bodies in the greater omentum biopsy.
How to distinguish malignant omental infiltration from inflammatory thickening on CT?
Visually on CT, these conditions can be completely indistinguishable from one another. The interpretation of any findings must be carried out strictly taking into account the patient's clinical presentation.
Is macroscopic adipose tissue found in high-grade liposarcomas?
No, for high-grade variants (pleomorphic and round-cell liposarcomas), the presence of macroscopic fat is least likely.
What else to study on this topic
- Histological classification of abdominal liposarcomas
- Mesenteric fibromatosis in familial adenomatous polyposis
- Criteria for assessing therapeutic pathomorphosis in ovarian tumor chemotherapy
- CT semeiotics of jejunal ischemia in mesenteric tumor involvement
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