Primary omental pregnancy: case report

Omental pregnancy is a very rare form of ectopic pregnancy. Here we presented a case of primary omental pregnancy diagnosed at surgical exploration. A 28 year old woman submitted with severe abdominal pain, without any delay of menstruation. History of the patient revealed no use of contraceptive method. There was no gestational sac in the endometrial cavity and no tubal ring in the adnexa, but free peritoneal fluid in the pouch of Douglas was detected at ultrasonography. Laparotomy was done according to pre-operative diagnosis of ruptured tubal pregnancy. Bilateral tubes and ovaries were intact; omental pregnancy was detected and partial omentectomy was performed. Although 16 cases of omental pregnancy (mostly secondary) were reported in the literature, herein we describe a primary omental pregnancy without adnexial involvement.     

网膜囊上隐窝的横断层解剖

目的：为网膜囊脓肿的影像诊断及外科治疗提供形态学依据。方法：对30具成人尸体上腹部连续横断层标本进行观察。5具成人尸体于网膜囊内行乳胶灌注后，观察乳胶在网膜囊内的蔓延情况而作网膜囊整体探查。结果：探明了网膜囊上隐窝的周界，尤其是网膜囊上隐窝和肝尾状叶的关系。结论：掌握网膜囊上隐窝与肝尾状叶的位置关系对肝尾状叶周围的积液和肿块的诊断具有重要的影像学意义。     

Immature omental teratoma

Immature omental teratomas are extremely rare neoplasms. To our knowledge, only two cases have been reported in the literature. In some anatomic locations, the malignant potential of immature teratomas correlates with the presence and quantity of neuroectoderm within the tumor mass. We describe the first immature omental teratoma with prominent neuroectodermal differentiation.     

A supernumerary ovary of the omentum with cystic change: Report of two cases and review of the literature

A supernumerary ovary is a rare gynecological anomaly. Particularly rare is the presence of cystic changes within the supernumerary ovary. We report two cases of neonates found to have a supernumerary ovary resembling an omental cyst. To the best of our knowledge, this report describes the first antenatal diagnosis of an omental cyst with a supernumerary ovary. To explain this unusual occurrence, it is suggested that an omental cyst becomes detached from the ovarian tissue and implants itself in the greater omentum, and that these supernumerary ovaries are of true embryologic origin, and not due to post-surgical or post-inflammatory implantation.     

Primary peritoneal anaplastic giant cell carcinoma: case report of an unusual and highly malignant müllerian neoplasm

Virtually all primary peritoneal carcinomas (PPCs) are of serous papillary type. We report an unusual histologic type of PPC composed of anaplastic giant cells, which exhibited an aggressive clinical course. A 72-year-old woman presented with lower abdominal pain. Computed tomography showed a diffuse omental thickening. The patient underwent an exploratory laparotomy with omentectomy, total hysterectomy, bilateral salpingo-oophorectomy, and appendectomy. Pathologic examination revealed extensive omental replacement by tumor but only superficial surface cortical involvement of both ovaries, a disease distribution consistent with a typical müllerian-derived PPC. However, this neoplasm was composed of diffuse anaplastic tumor giant cells, rather than serous carcinoma, which is the usual histologic type encountered in PPC. The patient died within 1 month after surgery. We report this unusual histologic variant of PPC to raise awareness that anaplastic giant cell carcinoma may arise in the pelvic peritoneum as a primary tumor.     

Gastrointestinal stromal tumors: an ultrastructural study

Gastrointestinal stromal tumors (GISTs) represent an enigmatic group of lesions of uncertain phenotype and biologic potential. Although earlier studies suggested smooth muscle cells, schwann cells, or neuronal differentiation, more recent evidence indicates that these tumors show phenotypic features that are similar to the interstitial cells of Cajal. Recently, investigators have begun to evaluate these lesions in a site-specific manner and have found that, in addition to morphologic differences between them, their biologic behavior also appears to be linked to their anatomic location. Many of these studies have emphasized the histologic and immunophenotypic features of GISTs in relation to their sites of origin, however, their site-specific ultrastructural characteristics have received little attention in the literature. In this study, we evaluated 34 GISTs (15 gastric, 12 small intestinal, 4 colonic, and 3 omental) for a variety of ultrastructural features in an effort to identify site-specific similarities and differences. Tumors predominantly composed of epithelioid cells were more commonly seen in gastric (60%) and omental (67%) tumors than in those of the small intestine (33%) and colon (0%). Cytoplasmic filaments and intercellular junctions were commonly seen in tumors from all locations, the filaments frequently forming paranuclear aggregates in the epithelioid cells. Tumors from all sites were composed of cells with surface filopodia and interdigitating cell processes, but in tumors of the stomach and omentum the filopodia were usually short and minimally intertwined, whereas those of small and large intestinal GISTs were characteristically long and complex. Basal lamina, though poorly formed, was present only in tumors of gastric and omental origin (13% and 67%, respectively). Pinocytotic vesicles were also seen in tumors from these sites (33% of gastric tumors and 67% of omental lesions) as well as those of the small intestine (17%) and the colon (25%). None of the gastric or omental tumors had microtubules; they were, however, seen in small intestinal (33%) and colonic (25%) stromal tumors. Skenoid fibers were seen in 33% of small intestinal GISTs and 1 metastatic gastric GIST. Overall, gastric and omental tumors have better developed features of myogenic differentiation and have blunt filopodia and minimally intertwined cell processes. Indeed, these 2 groups are indistinguishable ultrastructurally, raising the possibility that the genesis of omental GISTs is similar to that of gastric stromal tumors. Small intestinal stromal tumors have characteristic interdigitating cell processes and numerous elongate filopodia-like structures harboring intercellular junctions as well as microtubules and extracellular skenoid fibers. The constituent cells in colonic stromal tumors, while more reminiscent of small intestinal stromal, were frequently more primitive in appearance. In conclusion, GISTs from different anatomic locations share many overlapping ultrastructural characteristics; however, a few features are distinctive. It is hoped that these findings will aid in their recognition and contribute to the classification of this heterogeneous group of neoplasms.     

Recurrent prostate carcinoma presenting as omental large cell carcinoma with neuroendocrine differentiation and resulting in bowel obstruction

Neuroendocrine differentiation in the neoplastic prostate varies from foci of adenocarcinoma showing immunoreactivity to the pure small cell carcinoma, which correlates with poor prognosis. Widely metastatic disease in unusual sites is reported for small cell carcinoma, and rarely is the serum prostate-specific antigen level elevated. We report a case of recurrent prostate adenocarcinoma presenting as bowel obstruction due to widespread metastatic disease in the omentum and peritoneum. The histopathology of the omental metastasis was that of a large cell neuroendocrine carcinoma, without evidence of an adenocarcinoma. The absence of a clinically evident second primary tumor, the concomitant elevated serum prostate-specific antigen level, and the positive tissue immunoreactivities to prostatic markers all supported the prostatic origin of the omental tumor. Review of the importance of prostatic neuroendocrine differentiation and its unusual metastatic patterns is presented.     

Primary omental tumor with ultrastructural features of cellular schwannoma and absence of S-100 antigen reactivity

We report a primary well-delimited, large mesenchymal omental neoplasm which appeared in a 58 year old man without neurofibromatous traces. The histological and ultrastructural features were consistent with a Schwann cell origin. However, repeated immunohistochemical reactions failed to demonstrate protein S-100 antigen reactivity in the neoplastic cells, the latter only expressing vimentin. The differential diagnosis with hemangiopericytoma is proposed.     

Omental cyst in children presenting as pseudoascites: report of two cases and review of the literature

An omental cyst is a rare intra-abdominal lesion. Absence of characteristic clinical findings make the diagnosis difficult. These cases are reported because of its rarity. The brief review of the features of omental cyst is included in order to increase awareness of this entity.     

高血压病患者大网膜小动脉重塑的观测及相关蛋白表达探讨

目的: 研究高血压病患者大网膜小动脉病理损害、重塑及相关蛋白的表达。方法: 检测12例非高血压病对照者和12例高血压病患者血液流变学及大网膜小动脉形态学的变化,采用免疫组织化学方法检测大网膜小动脉Bcl-2、Bax、c-Myc、c-Fos、MMP-9和TIMP-2蛋白表达,用Masson染色法观察大网膜小动脉壁胶原含量变化。结果: 高血压病患者血液流变学异常,大网膜小动脉胶原沉积增多,中膜厚度/管腔直径比值增大,动脉壁Bcl-2、Bax、c-Myc、c-Fos、MMP-9和TIMP-2蛋白表达增强。结论: 高血压病患者大网膜小动脉存在病理损害和重塑,其机制与血液动力学(高血压)和血液流变学异常,动脉壁Bcl-2和Bax、MMP-9和TIMP-2表达失衡及c-Myc和c-Fos过度表达有关。     

Proliferative activity of macrophages in the greater omentum of the mouse in relation to the early postnatal development of the vascular structures

The rudimental omentum in newborn mice presents itself as a thin, poorly vascularized membrane covering the stomach. Imprints and whole mounted preparations of the omental membrane of mice from seven different inbred strains, aged 1-10 days, were made and sequential morphological changes were described. It was found that omentum of suckling mice contains numerous foci or colonies of mononuclear phagocytes (omental macrophages). These cells reveal a high proliferative activity when examined 1 hr after exposure of tritiated thymidine. The labeling index in the population of omental macrophages is variable, ranging in individual mice from less than 5% to 25%. This wide variation is a nonrandom phenomenon. It was found in all seven strains of mice and depends mainly on the age of the mouse. Two possible interpretations are as follows: Some interrelation exists between the intensity of the proliferative activity of omental macrophages and the development of vascular and lymphoid structures that are characteristic for the omentum of adult mice. Omental macrophages originate from local precursors that are not dependent on the bone marrow.     

Omentopexy for limb salvage in Buerger's disease: indications, technique and results

Buerger's disease is a limb-threatening condition occurring in the young and productive age group and its management has always been a challenging problem. A large number of medical and surgical options have been suggested, but the quest for an ideal solution to this problem continues. Omentopexy for Buerger's disease is an attractive option, which is rapidly gaining popularity. We discuss the historical aspects, technical considerations and results of omental transfer for this limb-threatening condition. In doing so, the relevant literature on the subject has been extensively reviewed. In all published series, there has been marked improvement in intermittent claudication and rest pain. Ischaemic ulcers have healed and the progression of gangrene has stopped. If carried out with the complete understanding of the anatomy of the omental vascular arcade, the results of omentopexy are gratifying, thus avoiding amputation and conserving the limb.     

Abdominal distention due to omental bursitis in a calf

There are many potential causes of abdominal distention in cattle, among which, omental bursitis is a rare condition. Abdominal distention due to omental bursa inflammation was diagnosed in a 6-month-old Holstein calf. Clinical signs included severe abdominal distention, weakness, and diarrhea. Exploratory laparotomy was carried out at the midline and a large quantity of exudate was drained. α-Hemolytic streptococcus was cultured from the exudate. In accordance with the wishes of the owner, the calf was euthanized at an abattoir. At necropsy, ulcers in the abomasum were found together with one metallic foreign body that penetrated to the reticular wall. This report indicates that omental bursitis should be considered in the differential diagnosis for calves with signs of abdominal distention.     

Possible role of milky spots in mesothelial transplantation

Milky spots are very small omental organs, in contact with peritoneal membrane, devoid of capsule and consisting of macrophages, lymphocytes and a few plasma cells supported by blood and lymphatic vessels. The exact role of these particular organs is still not clear, but they are similar to lymphatic structures and it is clear that they play a role in peritoneal infection and abdominal tumors. Peritoneal dialysis seems to activate the milky spots changing their morphology. The authors try to formulate some hypotheses on the role played by these little omental organs during autologous mesothelial transplant.     

Primary torsion of the greater omentum

Primary omental torsion is a rare cause of acute abdominal pain. A case of omental torsion in a 49-year-old woman who presented with clinical features consistent with acute appendicitis is discussed with a review of the literature.     

Invariant NKT cells and CD1d+ cells amass in human omentum and are depleted in patients with cancer and obesity

Invariant NKT (iNKT) cells recognize lipid antigens presented by CD1d and respond rapidly by killing tumor cells and release cytokines that activate and regulate adaptive immune responses. They are essential for tumor rejection in various mouse models, but clinical trials in humans involving iNKT cells have been less successful, partly due to their rarity in humans compared with mice. Here we describe an accumulation of functional iNKT cells in human omentum, a migratory organ with healing properties. Analysis of 39 omental samples revealed that T cells are the predominant lymphoid cell type and of these, 10% expressed the invariant Vα24Jα18 TCR chain, found on iNKT cells, higher than in any other human organ tested to date. About 15% of omental hematopoietic cells expressed CD1d, compared with 1% in blood (p<0.001). Enriched omental iNKT cells killed CD1d⁺ targets and released IFN‐γ and IL‐4 upon activation. Omental iNKT‐cell frequencies were lower in patients with severe obesity (p=0.005), and with colorectal carcinoma (p=0.004) compared with lean healthy subjects. These data suggest a novel role for the omentum in immune regulation and tumor immunity and identify it as a potential source of iNKT cells for therapeutic use.     

Primary extramedullary plasmacytoma of the omentum associated with recurrent adenocarcinoma of the colon: First case report

Extramedullary plasmacytomas are rare tumors, with 272 cases reported in the literature in English. Less than 10 per cent of these are located in the gastrointestinal tract. This report documents the first primary plasmacytoma of the omentum in association with a recurrent colonic adenocarcinoma. Extramedullary plasmacytoma, a B cell neoplasm, characteristically arises in areas containing lymphoid tissue. In our case the tumor most likely arose in a lymph node or nodes in the omental fat, with subsequent replacement of the entire greater omentum and involvement of the colonic serosa by direct extension. Although the extent and nature of the association between myeloma and carcinoma remain obscure, a review of the literature suggests that such association may occur more frequently than has been supposed. Further investigation would appear to be warranted.     

Different metabolic regulation by adenosine in omental and subcutaneous adipose tissue

Adenosine content was higher in omental adipose tissue (0.91 +/- 0.13 nmol g-1 of wet weight; mean +/- S.E.M.) than in abdominal subcutaneous adipose tissue (0.42 +/- 0.08 nmol g-1 of wet weight) in rapidly frozen surgical biopsy samples taken from ten patients undergoing elective abdominal surgery. This difference was statistically significant (P less than 0.002). The sensitivity of isoprenaline-stimulated lipolysis to inhibition by N6-(phenylisopropyl)adenosine was studied in omental and abdominal subcutaneous adipocytes isolated from nine patients. The effect of this adenosine Ri-site agonist was less pronounced in omental than in abdominal subcutaneous adipocytes which could be due to a desensitization phenomenon. This difference was statistically significant (P = 0.012). The ratio of the inhibitory guanine nucleotide binding proteins Gi1 and Gi2 to the corresponding stimulatory protein Gs was the same in plasma membranes prepared from omental and abdominal subcutaneous adipocytes. In conclusion, in omental adipose tissue, adenosine content is higher and the response to this nucleoside is less pronounced than in subcutaneous adipocytes. This difference cannot be explained by a different (Gi1 + Gi2)/Gs ratio.     

Ovarian and omental ependymomas in peritoneal washings: cytologic and immunocytochemical features

The cytologic findings in peritoneal washings of two women, one of whom had an ovarian ependymoma and the other a primary omental ependymoma, are reported. The ependymomas were characterized by the presence of numerous, isolated, spindle and stellate cells as well as groups of cells forming true rosettes. The tumor cells displayed slightly pleomorphic, round-to-oval eccentric nuclei and abundant fibrillary cytoplasm with tapering cytoplasmic processes. In addition, one of the patients had numerous papillae and cell clusters with associated psammoma bodies indistinguishable from those found in low-grade serous carcinoma. The demonstration of glial fibrillary acidic protein (GFAP) in both cases by immunocytochemical procedures indicates the usefulness of this method in cytologic preparations to confirm the diagnosis of these uncommon neoplasms.