Seeded Metastases on the Greater Omentum

A characteristic feature of the greater omentum, projecting as the fatty apron of the abdomen, is its associated lymphoid tissue, known as milky spots. These are composed of numerous macrophage and lymphocyte aggregations surrounding a capillary convolution.167,168 The mesothelial cells overlying these areas are loosely connected and lack basement membranes.169171 They act as open lymphatic lacunae that absorb peritoneal fluid and thereby bring tumor cells in large quantity to this struc-

172 173

ture. ' The secretion of angiogenetic factors by omental tissue may result in early vascularization of the seeded tumors and, therefore, their more rapid growth.174 This results in the omental cake.

In disseminated carcinomatosis, most commonly from ovarian carcinoma, seeded metastases on the greater omentum may be readily evident by sectional imaging. The lesions range from soft-tissue permeation

Fig. 4-181. Intrahepatic metastasis simulated by extracapsular lesion.

A lesion is seen dorsally seemingly involving the right lobe (arrow). This was proved to be a metastasis to the diaphragm from ovarian carcinoma. The liver parenchyma and the liver capsule were both free from tumor in this area. (From Lundstedt et al.

Intrahepatic Lesion

Fig. 4-182. Intrahepatic metastasis mimicked by extracapsular lesion.

(a) CT shows an appearance strongly suggesting a peripheral intrahepatic cystic metastasis, secondary to ovarian carcinoma.

(b) Lower level more clearly indicates true nature of extracapsular metastases, associated with diaphragmatic peritoneal thickening.

Fig. 4-182. Intrahepatic metastasis mimicked by extracapsular lesion.

(a) CT shows an appearance strongly suggesting a peripheral intrahepatic cystic metastasis, secondary to ovarian carcinoma.

(b) Lower level more clearly indicates true nature of extracapsular metastases, associated with diaphragmatic peritoneal thickening.

of omental fat to discrete linear and nodular densities (Fig. 4-183) to thick, solid omental masses described as "caking"137,175,176 (Figs. 4-184 and 4-185). Widespread peritoneal metastasis, including omental infiltration, is a rare consequence of a retroperitoneal malignancy such as renal cell carcinoma.177 A densely calcified omental cake secondary to a metastatic serous cystadenocarci-noma of the ovary rich in psammoma bodies has been reported.160

Heavily seeded metastatic deposits on the greater omentum are to be distinguished from primary neo-plasms,178,179 infection and inflammation (Fig. 4-186), consequences of trauma, varices (Fig. 4-187), and in-farction.179,180

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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