Malignant smooth muscle tumors of the retroperitoneum and mesentery: a clinicopathologic analysis of 44 cases

Forty-four cases of leiomyosarcoma arising in the retroperitoneum (33 cases) and mesentery (11 cases) were analyzed clinicopathologically, and four were examined ultrastructurally. These tumors were more common in women (61%) than in men (39%), and the median age of the patients was 59 years. Except for three tumors, most were large and over 10 cm in the greatest diameter. Twenty-seven tumors were classical leiomyosarcomas, while seven were composed predominantly of epithelioid cells and classified as malignant leiomyoblastoma (epithelioid leiomyosarcoma). In addition to the classical microscopic features, dedifferentiated areas resembling malignant fibrous histiocytoma were noted in three cases. Ultrastructurally, the tumors were characterized by smooth muscle tumor cells showing a spectrum of differentiation of varying degrees. Of the 42 patients for whom follow-up information could be obtained, 33 (79%) died within a period of five years after the initial treatment. Mitotic activity showed no significant correlation with biological behavior; ten of the 15 patients in whom the mitotic counts were less than five per 10 high-power fields (HPF), expired of the tumor.

Peritoneal endometriosis: scanning electron microscopy and histology of minimal pelvic endometriotic lesions

In 36 patients with laparoscopically diagnosed endometriosis, biopsies were taken from different areas of the pelvic peritoneum bearing foci of endometriosis. The biopsies were studied by scanning electron microscopy and by light microscopy. Combined use of these techniques resulted in the differentiation of three topographically and morphologically different types of endometriotic lesions: intraperitoneal endometriotic polyps with no glandular openings but associated with deeper endometriotic glands and stroma; intraperitoneal endometriotic foci with surface epithelium, glands, and stroma; and retroperitoneal small lesions with few glands and scant stroma. The morphologic features of endometriotic foci indicate that they do not follow the typical cyclic changes described for the uterine endometrium. Our microanatomic characterization of endometriosis is discussed in relation to the conflicting data concerning peritoneal fluid constituents and infertility in patients with minimal endometriotic lesions.

Morphology of peritumoral proteoglycan alterations in the rabbit mesentery invaded by V2 carcinoma cells

After intraperitoneal implantation into Swiss Silver rabbits, V2 rabbit carcinoma cells invade the mesentery where they form nodules of different size and texture: compact (less than 120 microns in diameter), loose (120-250 microns) and mixed (above 200 microns). Together with tumor development, certain changes take place in the loose connective tissue of the mesentery. Application of TEM, together with use of safranin O, has shown that, in areas free of tumor growth, collagen bundles become thick and heavy and proteoglycan density is increased. Concurrently, the number of fibrocytes, now transformed to fibroblasts, increases. Small, compact nodules are surrounded by a concentrically arranged extracellular matrix. Its overall density is similar to that of nodule-free areas. In the immediate vicinity of large, loose nodules, all constituents of the extracellular matrix disappear. Adjacent connective tissue is partly destroyed but still contains collagen fibers and proteoglycans. These findings suggest the following: The presence of V2 carcinoma cells induces marked alterations in the structured and non-structured components of the extracellular matrix. These changes are, at the same time, progressive and regressive and the occurrence of one or the other depends on local tumor progression. Progressive alterations may result from an increased activity of fibroblasts. Since degradative effects, on the other hand, are only seen in the immediate vicinity of larger tumor aggregates, it is assumed that a minimal number of tumor cells is essential for destruction of extracellular matrix.

Malignant peritoneal mesothelioma with massive foamy cells. Codfish roe-like mesothelioma

An autopsy case of a 45 years old Japanese female with malignant masothelioma showing peculiar stromal change was presented. The tumor had occupied the abdominal cavity around the uterus and both ovaries, and was diagnosed as a malignant peritoneal mesothelioma of epithelial type. The characteristic feature of the tumor was that the foam cells, which contained abundant amount of lipid droplets in the cytoplasm, and were thought to be histiocytes, massively occupied the stroma of the papillary tumor. Macroscopically, the tumor simulated a codfish roe. To our knowledge, no case of this sort of appearance of mesothelioma has ever been reported.

Primary omental leiomyosarcoma masquerading as hemorrhagic ascites

An 85-year-old man with unexplained hemorrhagic pseudoascites of four years' duration was discovered to have a primary omental leiomyosarcoma. Neoplasms arising in the greater omentum are rare. To date, only three primary omental leiomyosarcomas have been described. Clinical and pathologic findings of this case are presented and the topic of primary omental neoplasms is reviewed.

Ultrastructure of poorly differentiated diffuse epithelial mesotheliomas

In differentiating diffuse epithelial mesothelioma from metastatic adenocarcinoma in pleural and peritoneal biopsies, the number and form of microvilli and the amount and distribution of tonofilaments are thought to be the most useful criteria. This report details 5 cases of diffuse epithelial mesothelioma in which the characteristic fine structural features of neoplastic mesothelial cells were markedly modified. The majority or all tumor cells were poorly differentiated in electron micrographs, particularly with reduced prominence or absence of intermediate filaments, desmosomes, intracytoplasmic lumina, and microvilli. Immunohistochemistry revealed the absence of carcinoembryonic antigen and the presence of cytokeratin in all cases. Comparison with a better differentiated case suggests cytologic details that are useful in distinguishing the poorly differentiated type of epithelial mesotheliomas from adenocarcinoma. These include a mosaic pattern of closely associated tumor cells with a few long, narrow cytoplasmic processes lying parallel to adjacent plasma membranes, abundant cytoplasm with limited organelles usually having a polar arrangement, and nuclei with markedly disaggregated chromatin and prominent nucleolonemal-type nuclei.

Occluding junctions in an epithelioid mesothelioma: a freeze-fracture study

The presence of a well-developed tight junction system in a case of diffuse, papillary, malignant mesothelioma of the peritoneum is documented using the freeze-fracture methodology. The mean number of strands within the tight junction network was determined to be 3.83 +/- 0.16. In addition, the tight junctions were specifically located in regions of the plasma membrane adjacent to recognizable microvilli. Gap junctions and desmosomes were found in close association with the occluding complexes; however, they were also seen in areas of the plasma membrane quite distinct from those that exhibit tight junction differentiation. The possible significance of the presence of tight junctions in neoplastic epithelial cells is also discussed.

Morphological studies on V2 carcinoma invasion and tumor-associated connective tissue changes in the rabbit mesentery

The mesentery is a duplicature of the peritoneum consisting of loose connective tissue and covered on both sides by mesothelium. Rabbit V2 carcinoma cells implanted i.p. adhere to the mesenteric surface between contracted mesothelial cells. While invasion from these sites sets in, progressive changes of the connective tissue, reflecting fibroblast stimulation, become apparent and comprise multiplication of connective tissue cells, transformation of fibrocytes into fibroblasts, and enhanced production of fibrillar and nonfibrillar constituents of the extracellular matrix. Tumor invasion into this increasingly dense tissue proceeds in 2 ways. (a) Single cells penetrate into and locomote within the interior, where they divide and give rise to nodules which become surrounded by zones of tissue destruction. (b) Proliferation of surface-attached tumor cells results in the formation of nodules which, preceded by zones of tissue damage, extend into the interior. While evidence for lytic effects in the microenvironment of single tumor cells is lacking, degradation of the fibrillar extracellular matrix is regularly found around tumor nodules and indicates a collective lytic action achieved by tumor cells and, possibly, host cells. These morphological findings are discussed in relation to published bio- and histochemical data on spread of the V2 carcinoma.

[Pseudomyxoma peritonei: a case with multiple metastases. Ultrastructural study and chemical analysis of the mucoid substance]

A patient with spreading pseudomyxoma peritonei probably caused by a tumor of the appendix showing suggestive clinical features is presented. The long evolution was marked by the discovery of gelatinous substance in the stools and in the lumen of the gut, and the appearance of distant metastasis in the lungs, adrenal glands and lymph nodes. Histochemical studies showed that periodic Shiff acid and Alcian blue were fixed by the mucoid substance. The use of toluidin blue (pH 1) revealed metachromosia. Electron microscopy ascertained the presence of enterocytes and mucous cells and revealed a more obvious nuclear disorganisation than by histological microscopy. Biochemical study showed that the mucoid substance extracted from the pseudomyxoma was rich in carbohydrates and could be identified as a mucin on the basis of the composition of its monosaccarides and of the alkali-lability of its glycanprotein linkages. The mucin was weakly hydrolysed by trypsin in vitro but was deeply attacked by the same enzyme after desialylation. These results: a) confirm the possibility of observing spreading distant metastasis in the pseudomyxoma peritonei; b) underline the potential interest of electron microscopic study in case of wavering diagnosis; c) show that the mucoid substance belongs to the group of neutral sulfomucins; d) legitimate, in the future, a trial of palliative treatment by neuraminidase in such cases.

Granulocytic sarcoma of the peritoneum

Granulocytic sarcoma is an unusual extramedullary tumor composed of immature cells of the myelogenous series; it usually occurs during the course of myelogenous leukemia. This paper presents a rare case of granulocytic sarcoma of the peritoneum, occurring without evidence of myelogenous leukemia in peripheral blood and bone marrow.

Observations on induced carcinosis peritonei of the Guinea pig

A diethylnitrosamine-induced hepatocellular carcinoma cell suspension (line-10), injected intraperitoneally in Sewall Wright strain-2 guinea pigs, causes ascites with implantation of malignant cells on the peritoneal surface. At these sites, swelling of the mesothelial cells and simultaneous proliferation of underlying fibroblasts and capillaries are seen. When there are about four layers of malignant cells and the mesothelial lining is disrupted, papillary projections of fibroblasts with capillaries, covered by malignant cells develop. These begin to behave as a "tissue". In these areas basement membrane destruction and lymphatic and blood vessel infiltration are demonstrable. These developments have been investigated by light microscopy, histochemistry, transmission- and scanning electron microscopy.

[Disseminated peritoneal leiomyomatosis. Light and electron microscopic study]

The rare case of disseminated peritoneal leiomyomatosis is reported. A 41 year old non-gravid patient had a laparotomy for uterine fibroids and numerous subperitoneal nodules were found in the abdominal cavity. The light and electron microscopic examinations showed disseminated peritoneal leiomyomatosis. The nodular proliferation of the sub-peritoneal stroma is characteristic for this disease. The patient is free of problems three years following the initial diagnosis of disseminated peritoneal leiomyomatosis.

Comparative light and electron microscopic studies of cystic and papillary tumors of the peritoneum

Using a cystic lymphangioma of the greater omentum and a benign cystic mesothelioma as examples, the distinguishing characteristics of cystic peritoneal tumors are shown, using light microscopic and ultrastructural findings. A benign papillary mesothelioma is used for comparison. The cellular structures and growth rate of the mesotheliomas are contrasted with the tissue reactions which are typical for irritated serosa. The diffusely growing papillary mesothelioma is a very rare tumor, the cells of which are similar to normal serosa cells, but also show characteristics of other benign or malignant mesothelial tumors and of reactive proliferated mesothelial cells. The diffusely growing benign cystic mesothelioma has only been described in isolated cases and is characterized by cysts grouped in acini with mainly flat, localized cuboidal cell lining. The histochemical properties and cytological findings correspond closely to those of the papillary tumor or normal peritoneal lining cells. In contrast, the cystic lymphangioma probably represents a congenital defect with a slow growth rate. The structure is characterized by a sponge-like arrangement of smooth-walled cysts, in the walls of which smooth muscle cells and lymph follicles are embedded. The endothelium is also flat and ultrastructurally resembles that of lymph vessels.

[Malignant mesothelioma. Retrospective study of 16 cases]

Sixteen cases of malignant mesothelioma (13 pleural and 3 peritoneal) are reported. Fifteen cases were autopsied; in one case only biopsy material was available which are studied by electron microscopy. Among the autopsy cases, 12 had had previous biopsies, one had undergone multiple cytological examinations and 2 cases only one cytological examination. It was concluded that clinical signs and symptoms of mesothelioma were not specific and did not allow the diagnosis. For differential diagnosis as between mesothelioma and metastatic carcinoma, biopsy seemed to be more reliable that exfoliative cytology. Alcian blue stain after hyaluronidase digestion is a reliable test in the diagnosis of mesothelioma only when alcian blue is positive initially. However, in half of our mesothelioma cases this stain remained negative. Electron microscopic study appeared to be a satisfactory method of differentiating between malignant mesothelioma and metastatic carcinoma.

A mixed tumor of the omentum majus in an adult with discussion related to hepatoblastoma

A mixed tumor of the omentum majus found at autopsy of a 28-year-old man with a huge liver tumor is described. The primary tumor was identified in the omentum majus by macroscopic, histologic and electron-=microscopic observations. The tumor was finally diagnosed as a mixed tumor which resembled a hepatoblastoma consisting of immature and embryonal types of epithelial component and of mesodermal tumor including hemangioma, osteoid and myxomatous tissues in the primary lesion. Widespread multiple metastases of the epithelial component mainly to the liver, and partially in the lungs, diaphragm and lymph nodes were noted. The levels of alpha-fetoprotein and carcinoembryonic antigen were within normal limits, but the epithelial component showed a resemblance to primitive hepatocytes. This tumor was discussed related to hepatoblastoma in an adult, with the features compatible with description of the same tumors reported previously in the literature.

[Experimental studies on ascites tumor of human osteosarcoma in nude mice (author's transl)]

Six human osteosarcomas were transplanted subcutaneously in the back of nude mice and three of the six were found to be serially transplantable. Two of three transplantable solid tumors were called DOS tumor and KOS tumor. The 4th generation of DOS tumor and the 1st generation of KOS tumor grew to invade the peritoneum and tumor cells were spilt spontaneously into the abdominal cavity. These two cases were transformed to ascites tumor, called DOS-NM ascites tumor and KOS-NM ascites tumor. They were found to be serially transplantable by an intraperitoneal injection of free tumor cells (10-20 x 10(5) cells). DOS-NM and KOS-NM ascites tumor cells were analysed to have human karyotype and alkaline phosphatase activity. Ascites tumor cells were studied under light and electron microscopes. A large number of elongated and ballooned mitochondria were characteristically seen in the cytoplasm of two ascites tumor cells by electron microscope. Development of rough surfaced endoplasmic reticulum and Golgi's apparatus was poor, and no production of collagen fiber was seen in these materials. There is no report referring to ascites tumor of human osteosarcoma, therefore ascites tumor of osteosarcoma was made deliberately and the following results were obtained. 1) Several blocks of DOS tumor were implanted intraperitoneally into 5 nude mice, and only solid tumors grew in the abdominal cavity without ascites. 2) Minced DOS tumor was implanted subcutaneously close to the peritoneum and 2 out of 6 nude mice developed ascites tumor. 3) Cell suspension of DOS tumor was injected intraperitoneally and 3 out of 4 nude mice developed ascites tumors. As mentioned above, human osteosarcoma was successfully induced to ascites tumor (DOS-NM), which was established earlier compared with solid tumor (DOS). Characteristics of human osteosarcoma are easily examined with ascites tumor and in vivo screening test of anticancer drugs can be quantitatively done. Therefore ascites tumor is considered to be a valuable experimental model.

Secreting peritoneal mesothelioma. Report of a case with cytological, ultrastructural, morphometric and histological studies

A 29 year old woman, living in an area with a high level of asbestos exposure, developed the clinical features of peritoneal mesothelioma. The quantitative cytological features differed from those of other mesotheliomas described in the literature in that the tumor cells had a large amount of vacuolated cytoplasm and an extremely low N/C ratio, resulting in a "benign" appearance. The ultrastructural study provided evidence for the production and accumulation of secretory products (mucolipids) by the tumor cells. Treatment with chemotherapy and radiation resulted in temporary remission, lasting for 20 months. However the patient then developed pulmonary involvement of the carcinomatosa a form and pleural tumors. The cytological pattern and the morphometric features of the metastatic floating malignant mesothelial cells in the pleural fluid closely resembled those of the primary peritoneal tumor. This case appears to be an example of secretory peritoneal mesothelioma with a bad prognosis, not withstanding the well-differentiated appearance of the tumor cells.

Benign papillary mesothelioma of peritoneum: a histological, histochemical and ultrastructural study of six cases

Six cases of localized benign papillary mesothelioma of peritoneum were retrieved from laboratory files over a 20-year period. One presented because of pain following torsion and the remaining five were incidental findings at operation. Light microscopy showed a delicate papillary stroma covered by a single layer of mesothelial cells. The mesothelial cells often showed punctate periodic acid-Schiff staining of cytoplasm. The brush border and stroma showed alcian blue positive staining which was abrogated by prior incubation with hyaluronidase. Electron microscopy revealed typical features of mesothelial cells with long microvilli, rough endoplasmic reticulum in relation to mitochondria, bundles of microfilaments, and tight junctions. Between cells there was a series of intercommunicating channels containing occasional lymphocytes and debris. These features are compared with nodular mesothelial hyperplasia, malignant mesothelioma and adenomatoid tumours of the genital tract. The necessity to distinguish benign papillary mesothelioma from metastatic carcinoma is stressed and relies on the recognition of their mesothelial origin.

Mesenteric lymphangioma. A case report with transmission and scanning electron microscopic studies

A mesenteric lymphangioma was found in a 2-day-old newborn, thus attesting to the congenital nature of the lesion. The ultrastructural features of the tumor included a poorly developed, discontinuous basal lamina, and anchoring fibrils distinguished it from a hemangioma. An undulating surface of the endothelium and prominent grooving between the endothelial cells were found by scanning electron microscopy and were indistinguishable from arterial and lymphatic endothelial surfaces that have been studied by others.

Ultrastructure and steroid-binding studies in leiomyomatosis peritonealis disseminata

Leiomyomatosis peritonealis disseminata (LPD) is characterized by the development of numerous leiomyomata throughout the peritoneal cavity which appear grossly malignant but histologically benign. The etiology of this disorder has been controversial. The tenth reported case of LPD is presented with ultrastructural evidence that these tumors arise from smooth muscle cells. The cytoplasmic estrogen and progesterone bindings by these tumors were ninefold and twofold greater than receptor concentrations in normal myometrium from the same patient. In addition to the steroid binding data, the strong association of this disorder with pregnancy or, as in this case, oral contraceptives suggests that the stimulus for neoplastic initiation and growth is hormonally related.

Endometriosis occurring in leiomyomatosis peritonealis disseminata: ultrastructural study and histogenetic consideration

Leiomyomatosis peritonealis disseminata is a pseudomalignant condition which mimics disseminated abdominal carcinoma. A new case is reported and compared to the 11 well-documented cases in the literature. All reported patients have experienced a benign clinical course. The peritoneal nodules are composed of histologically benign-appearing smooth-muscle cells, substantiated by electron-microscopic study. The histogenesis of this entity is discussed in the light of our ultrastructural findings and the observation of concurrent endometriosis. The theory of metaplasia of the subcoelomic mesenchyme in the pathogenesis of the leiomyomatous lesions is favored. The serum estrogen levels determined in our patient did not reveal any abnormal change. The inducing factor(s) remain to be identified. Also, an unusual sensitivity of the coelomic tissues in these patients, in response to metaplastic stimuli, is postulated as a possible contributing factor.

A scanning electron microscopic study on the peritoneal implantation of ascites hepatoma AH100B cells in rats

The process and mechanism of peritoneal metastasis of tumor cells were studied experimentally by means of scanning or transmission electron microscopy, employing rat ascites hepatoma AH100B. Adhesion of tumor cells by microvilli and/or pseudopodia to the mesothelium was observed within 1 approximately 3 days after inoculation when there was no morphological changes of the mesothelial cells. Some changes of the mesothelial cells, such as irregularity, atrophy, and exfoliation, followed tumor cell adhesion 5 or 6 days after inoculation. It was noted that tumor cells adhered to the mesothelium first where no morphological changes were induced, and it is suggested that tumor cells infiltrate into the submesothelial tissue through mesothelial defects.

Multicystic, peritoneal mesothelioma: a report with electron microscopy of a case mimicking intra-abdominal cystic hygroma (lymphangioma)

A 27-year-old Caucasian female complained of persistent, poorly localized abdominal pain of several months' duration, found to be due to a multicystic diffuse lesion involving omentum, peritoneum and pelvic viscera. Three resections were required within a ten-month period for symptomatic control. The tumor showed many of the clinical, operative, gross and light microscopic features of intra-abdominal lymphagioma. Tissues removed at the third operation, however, were examined by electron microscopy, and found to consist of a myriad of small cysts and channels lined by mesothelial cells. In view of these findings, the lesion was regarded as a cystic peritoneal mesothelioma. Similarities between lymphangioma and peritoneal mesothelioma are discussed. It is suggested that electron microscopic examination of lining cells of cystic lesions which are considered grossly consistent with lymphagiomas may yield additional similar cases.

Multicystic, peritoneal mesothelioma: a report with electron microscopy of a case mimicking intra-abdominal cystic hygroma (lymphangioma)

A 27-year-old Caucasian female complained of persistent, poorly localized abdominal pain of several months' duration, found to be due to a multicystic diffuse lesion involving omentum, peritoneum and pelvic viscera. Three resections were required within a ten-month period for symptomatic control. The tumor showed many of the clinical, operative, gross and light microscopic features of intra-abdominal lymphagioma. Tissues removed at the third operation, however, were examined by electron microscopy, and found to consist of a myriad of small cysts and channels lined by mesothelial cells. In view of these findings, the lesion was regarded as a cystic peritoneal mesothelioma. Similarities between lymphangioma and peritoneal mesothelioma are discussed. It is suggested that electron microscopic examination of lining cells of cystic lesions which are considered grossly consistent with lymphagiomas may yield additional similar cases.

Leiomyomatosis peritonealis disseminata. An ultrastructural study

Electron microscopic features of the eighth documented case of leiomyomatosis peritonealis disseminata identify the main proliferative cell type as a mature leiomyocyte with all its associated ultrastructural features. The histogenesis of this neoplasm is considered to be a multicentric metaplastic change determined by an abnormal tissue response to the elevated hormonal levels occurring in pregnancy or ovarian functioning tumors. It is suggested that the cell of origin is the multipotent subcelomic mesenchymal cell, which retains the capacity to differentiate into several tissues, among them smooth muscle. To illustrate this possibility, myofibroblasts, cells with hybrid characters of fibroblasts and leiomyocytes, were observed; these may represent a transitional stage between the mesenchymal cell and the smooth muscle proliferating cell.

Fine structural study of annulate lamellae complexes in human tumors

Specific intracytoplasmic organelles, annulate lamellae and radial cisternae, have been studied in several human tumours. Annulate lamellae are observed in all cases of leiomyoma, leiomyosarcoma, rhabdomyosarcoma and malignant melanoma, whereas radial cisternae are only found in a case of leiomyosarcoma. Annulate lamellae are characterized by stacks of parallel arrayed long cisternae showing alternative arrangement of annuli and sacs. Some of these cisternae are connected directly with rough-surfaced endoplasmic reticulum and there is continuity with the lumen and membrane. Radial cisternae are mainly composed of two structures: numerous short cisternae, which are a variant of annulate lamellae, and numerous spherical particles derived from the cisternae. The cisternae are arranged parallel or radially around particles measuring up to 1100 A in diameter. These particles consisting of an amorphous high electron dense material without distinct limiting membrane are organized in groups and vary in number. There is no evidence of a direct relationship between these structures and viral infection.

Ultrastructure of human malignant diffuse mesothelioma

Eleven cases of malignant diffuse mesotheliomas, histologically classified into two groups, epithelial (5 pleural and 3 peritoneal) and biphasic or mixed (2 pleural and 1 peritoneal) forms, were stuied by electron microscopy to elucidate their ultrastructural characteristics. The neoplastic cells of the epithelial forms were varied in ultrastructure, from well differentiated (marked by polarity, micovilli, glycogen granules, junctional structures, tonofilaments, intracellular vacuoles, and a basement membrane) to poorly differentiated (which lacked some of these epithelial characteristics). In four of eight instances in epithelial type tumors, nonepithelial or mesenchymal neoplastic cells were recognized. The biphasic or mixed cases included three major cell types: epithelial, atypical epithelial, and mesenchymal. It appeared that there were transitional forms among the three cell types. The observations support the concept that the neoplastic cell of malignant mesothelioma can differentiate into a number of cell lines.