Embryonal carcinoma in the abdominal cavity of a male calf.

An embryonal carcinoma was diagnosed in the abdominal cavity of a 55-day-old male calf. Macroscopically, a large volume of ascitic fluid was observed along with white to yellowish-white masses of various sizes densely located on the abdominal wall and the surface of abdominal organs. There was an absence of testes in the scrotum. Histologically, the tumor cells were polygonal, and the tumor was mostly composed of sheets of densely packed solid patterns with occasional papillary and tubular structures. Cell nuclei were variable in size, and cellular mitotic rate was high. Immunohistochemically, tumor cells were positive for alpha-fetoprotein, placental alkaline phosphatase, cytokeratin, and carcinoembryonic antigen. Ultrastructurally, the tumor cells had large nuclei, extensive rough endoplasmic reticulum, and small numbers of mitochondria. Microvillus-like structures and desmosomes were occasionally observed. From lectin histochemical examination, the tumor cells were positive for concanavalin A, wheat germ agglutinin, peanut agglutinin, Dolichos biflorus agglutinin, soybean agglutinin, Griffonia simplicifolia I, and Bauhinia purpurea, and negative for Ulex europaeus agglutinin I. Results of histopathological, immunohistochemical, and ultrastructural examinations of the tumor were similar to those obtained for human embryonal carcinoma.

Hepatoid carcinoma of the skin: spontaneous rat skin hepatoid carcinoma with eosinophilic globules and crystals immunoreactive to alpha-1-antitrypsin.

We present a case of hepatoid carcinoma of the abdominal skin in a male Wistar rat. Histopathologically, this carcinoma resembled human hepatocellular carcinoma with respect to trabecular-sinusoidal structures. Carcinoma tissues contain numerous eosinophilic globules and crystals, and in this case, we found the characteristic eosinophilic globules in the hepatoid carcinoma cells and the crystals in the extracellular portions. Vivid carcinoma cells full of eosinophilic globules were present near the necrotic areas in tumor tissue, wherein quadrate crystals unstained with eosin were observed. PAS staining after diastase digestion revealed that the globules were PAS positive and diastase resistant. In addition, we found that the hepatoid carcinoma cells were immunoreactive for alpha-1-antitrypsin (anti-A1AT) antibody with the globules and crystals staining peripherally, and a central unstained region. Ultrastructural study of intracytoplasmic globules and extracellular crystals revealed that the fringe of each globule and crystal had no limiting membrane and showed the same level of electron density. These findings suggest that the characteristic crystals in this tumor may have originated from the globules that were emitted from the carcinoma cells after their death as a result of saturation with intracytoplasmic globules.

Malignant myopericytoma-like tumor in a Fischer rat.

Myopericytoma is a perivascular tumor that has been recently described in humans, but not in laboratory rodents. The authors encountered an intra-abdominal tumor resembling human malignant myopericytoma in a Fischer rat. Grossly, the tumor was found as two brown-colored masses located in the mesentery of rectum. Microscopically, the tumor was composed of oval to spindle-shaped cells, which were arranged in sheets around numerous thin-walled branching vessels and partly showed a concentric perivascular growth pattern. Mitoses were frequently seen, and the tumor cells showed a local invasion. Immunohistochemically, the tumor cells were strongly positive for alpha-smooth muscle actin and weakly positive for vimentin and desmin. Ultrastructurally, the tumor cells had dendritic processes, actin-like thin filaments with dense bodies, basement membranes, hemidesmosomes, and micropinocytotic vesicles. These findings suggest that the most appropriate term for diagnosis of the present case could be a malignant myopericytoma.

Intra-abdominal follicular dendritic cell sarcoma with marked pleomorphic features and aberrant expression of neuroendocrine markers: report of a case with immunohistochemical analysis.

Follicular dendritic cell sarcoma (FDCS) is a very rare malignant tumor arising most frequently in lymph nodes with only few reports of extranodal locations. We report the case of a 35-year-old man with a large retroperitoneal mass. Histologically the tumor was composed of highly pleomorphic cells exhibiting some uncommon features such as an epithelioid appearance, cystic spaces, and multinucleated cells with morphologic features of emperipolesis. Immunohistochemically the neoplastic cells were immunoreactive for CD21, CD23 and CD35. A previously unreported expression of neuroendocrine markers (Synaptophisyn and Neuron-Specific-Enolase) was present. Ultrastructurally no neuroendocrine secretory granules were detected. FDCS can mimic a wide variety of other malignant tumors, and a correct diagnosis requires exclusion of other neoplasms and immunohistochemical confirmation.

Round cell variant of myxoid liposarcoma in a Japanese Macaque (Macaca fuscata).

A 5-year-old, female, Japanese Macaque (Macaca fuscata) was diagnosed with round cell variant of myxoid liposarcoma. At necropsy, multifocal to coalescing, reddish tan to white nodules, ranging from 0.5 to 1 cm in diameter, were noted throughout the omentum and retroperitoneum. Similar neoplastic nodules were also present in diaphragm, abdominal wall, and on hepatic capsule. Microscopically, neoplastic masses consisted of round to polyhedral cells, which had round, often eccentric nuclei and abundant eosinophilic granular and microvacuolated cytoplasm; Oil red O staining demonstrated large numbers of lipid droplets in the cytoplasm. Ultrastructurally, the cytoplasm of the tumor cells was packed with occasional lipid vacuoles and numerous enlarged mitochondria. Immunohistochemistry revealed tumor cells were positive for vimentin, while negative to cytokeratin, actin, and Factor VIII-related antigen. To the authors' knowledge, this is the first report of round-cell variant of myxoid liposarcoma in nonhuman primate.

Morphological characterization of skin ganglion-like cells in Djungarian hamsters (Phodopus sungorus).

Characteristic ganglion-like cell proliferation observed in the skin of Djungarian hamsters was investigated using 24 male and 24 female hamsters, 1-6 months of age, to examine the anatomic location of these ganglion-like cells and their morphologic features. One abdominal skin tumor composed of these cells and resembling proliferative fasciitis in humans was also examined. Skin ganglion-like cells were rarely observed in young animals but increased in number and extent with age, especially in males. These cells were frequently seen in the ventral and medial regions of the trunk and legs rather than in the dorsal and lateral regions. Light microscopic examination of these ganglion-like cells revealed abundant vesicular basophilic cytoplasm with delicate intracytoplasmic silver stain-positive fibrils. Ultrastructurally, these cells contained abundant rough endoplasmic reticulum and Golgi complexes with dilated cisternae; intracellular collagen fibrils were present within these cisternae. Heat shock protein 47, beta-tubulin, and androgen receptor were expressed in these cells. The morphologic features of cells of one tumor resembling human proliferative fasciitis were identical to those observed in ganglion-like cells. The results of the present study suggest that these ganglion-like cells are derived from intrinsic undifferentiated mesenchymal cells in the dermis or subcutaneous adipose tissue and that any tumor-like lesion they form should be regarded as an abnormal proliferative lesion of skin ganglion-like cells rather than as proliferative fasciitis or fibroma.

Solitary fibrous tumor of the abdominal wall: a report of two cases immunohistochemical, flow cytometric, and ultrastructural studies and literature review.

Solitary fibrous tumors have been described at many extrapleural sites in recent years. However, solitary fibrous tumors arising from somatic soft tissue occur only rarely and can pose problems in the differential diagnosis from other benign or malignant soft tissue tumors. The majority of solitary fibrous tumors occurring in the somatic soft tissue have been found in the extremities and limb girdles, and the head and neck regions. There have been only eight published cases located in the abdominal wall. We herein report two female patients who developed solitary fibrous tumors of the abdominal wall that were not in association with the underlying peritoneum. Histologically, both tumors were characterized by a variety of architectural patterns, alternating hypercellular and hypocellular areas, proliferation of plump spindle cells, thick keloid-like and/or amianthoid collagen bundles, and ectatic staghorn-like vessels. Both tumors showed a diffuse strong reaction for CD34 and vimentin as well as focal positivity for bcl-2 and smooth muscle actin. A striking predominance in females was found in a literature review of solitary fibrous tumors of the abdominal wall, contrasting with other somatic soft tissue sites which show an equal gender distribution. Interestingly, expression of estrogen but not progesterone receptor was observed in both tumors. Ultrastructurally, the tumor cells displayed features of fibroblasts with dilated branching rough endoplasmic reticulum (RER) and Golgi apparatus. Both tumors assayed by flow cytometry demonstrated a diploid DNA content with an S-phase fraction of 7.9% and 11.4%, respectively. At follow up, both patients were well without evidence of recurrence or metastasis after surgical excision.

Deciduoid mesothelioma: a report of 5 cases and literature review.

Deciduoid mesothelioma was first described in young females and in the peritoneum, which led to the suggestion that deciduoid mesothelioma was a distinct subtype with specific clinical and pathologic features. Later reports, however, have shown that this type of mesothelioma may also occur in elderly people and in the pleura. Cases reported in the literature so far are limited, and the disease is not well defined. The authors report the histologic, immunohistochemical, ultrastructural, and clinical findings of 5 cases of deciduoid mesothelioma, and review the literature reports. The results demonstrate that the presence of numerous cytoplasmic intermediate filaments, either dispersed or bundled, appear to be the likely ultrastructural basis for the deciduoid histologic appearance. Twenty-one cases of deciduoid mesothelioma were identified in the literature. Analyses of these 21 cases and the authors' 5 cases showed an age range of 13-78 years (median 53 years) and a slight female predominance (female to male ratio of 1.4:1). Fourteen of 26 cases (54%) occurred in the peritoneum. Seven of 20 patients (35%) had a documented history of asbestos exposure. Fifteen of 20 patients died, with a mean survival time of 7.33 months (range 1-21 months). Five of 20 patients were alive at a follow-up time of 8 months to 5 years. These findings suggest that the so-called deciduoid mesothelioma has some clinical and pathologic features that are dissimilar to mesothelioma in general. Whether it truly represents a pathogenetically distinct variant or merely an expansion of the morphologic spectrum awaits further studies.

Trocar-site metastasis is not always due to laparoscopy.

The use of laparoscopic surgical techniques for the management of gynecologic malignancies has increased over the last years. Metastasis developing at the trocar insertion site is an emerging problem. We present the case of a 66-year-old woman with endometrial cancer who was diagnosed with an umbilical tumor after laparoscopically assisted vaginal hysterectomy (LAVH) and bilateral salpingoophorectomy. The interval between LAVH and diagnosis of the umbilical tumor was 13 months. The tumor was excised, and metastasis of endometrial cancer was histologically confirmed. Review of computer tomograms taken before LAVH showed a tumor in the umbilical area that had not been recognized before therapy. Therefore, tumor manifestation at the abdominal wall after laparoscopic surgery should not automatically be considered the result of iatrogenic spreading.

Spontaneous eosinophilic granulated round cell tumors in rats.

Morphologic and histochemical characteristics were noted for three spontaneous tumors with eosinophilic cytoplasmic granules that occurred in aged Fischer 344 rats. Macroscopic lesions were widely distributed in the body, mainly involving the intra-abdominal adipose tissue, pancreas, and mesenterium. These lesions were generally hard swellings with nodular and sclerosing areas. Bloody ascites was a concomitant finding. Histologically, the tumor cells were round, from 9 to 30 microm in diameter with one or two round to oval nuclei, and characterized by eosinophilic granules (0.5-2.0 microm) that stained definitely to weakly positive with the periodic acid-Schiff reaction and demonstrated no metachromasia with toluidine blue stain. Furthermore, the granules were characterized by a positive reaction with lectin histochemistry for concanavalin A (Con A), wheat germ agglutinin (WGA), phaseolus vulgaris agglutinin (PHA-E4), lens culinaris agglutinin (LCA), and recinus communis agglutinin (RCA-I) in all tumors and for ulex europaeus agglutinin (UEA-I), peanut agglutinin (PNA), and soybean agglutinin (SBA) in one tumor. Positive reactions for anti-rat mast cell protease II and CD8 were not demonstrated immunohistochemically. Abundant glycogen was noted in the large tumor cells from one rat. With electron microscopy, the cytoplasmic granules were identified as electron-dense homogenous bodies bounded by a single unit membrane. These characteristics are similar to those of granulated metrial gland cells, but further study is needed to clarify the cell of origin for these tumors.

Desmoplastic small round-cell tumor: a case report on the large cell variant with immunohistochemical, ultrastructural, and molecular genetic analysis.

examination. The patient died 10 months after surgery. Histologically, the tumor was composed of predominantly large epithelioid cells with foci of anaplasia mimicking metastatic carcinoma. Immunohistochemically, the tumor cells stained with anti-cytokeratin, EMA, desmin, and NSE antisera. Electron microscopy showed secretory lumina, desmosomes, cell processes with microtubules and electron-dense granules, and focal whorls of intermediate filaments. Reverse transcriptase-polymerase chain reaction performed on paraffin block-retrieved tissue demonstrated the EWS/WT-1 fusion transcript characteristic of the t(11;22)(p13;q12). This case illustrates a less common histological pattern of DSRCT, i.e., diffuse large cells, thus supporting the view that this tumor presents a wider morphological spectrum than that previously recognized.

Clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres: a novel member of the perivascular epithelioid clear cell family of tumors with a predilection for children and young adults.

The perivascular epithelioid cell family of tumors (PEComas), defined by their co-expression of melanocytic and muscle markers, includes angiomyolipoma, lymphangioleiomyoma, and clear cell "sugar" tumors of the lung, pancreas, and uterus. We present seven cases of a unique and previously unrecognized tumor of children and young adults, which represents a new addition to the PEComa group of tumors. Culled from three institutions over a 50-year period, all cases occurred in or immediately adjacent to the ligamentum teres and falciform ligament. Six patients were female and one male; their ages ranged from 3 to 21 years (median, 11 yrs). Tumor sizes ranged from 5 to 20 cm (median, 8 cm). All cases consisted of clear to faintly eosinophilic spindled cells arranged in fascicular and nested patterns. The cells had small but distinct nucleoli and low mitotic activity. Immunohistochemically, all cases were positive with antibodies to gp100 protein (HMB-45) and negative for S-100 protein. In three of the seven cases studied immunohistochemically, the tumors expressed smooth muscle actin, melan-A, microphthalmia transcription factor (MiTF), and myosin, but not desmin. No expression of the TSC2 gene product, tuberin, was seen in three cases. One case studied cytogenetically disclosed a t(3;10). Follow-up data, available in six of seven cases (median duration, 18 mos), showed five patients to be free of disease and one to have a radiographically presumed lung metastasis. We think these tumors comprise a new entity for which we propose the term "clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres." The differential diagnosis of these tumors includes clear cell sarcoma of tendons and aponeuroses, leiomyosarcoma, and angiomyolipoma.

Sarcoma of possible nerve sheath origin in a captive muskrat.

A captive adult female muskrat (Ondatra zibethicus) was found dead without previous signs of disease. At necropsy, abdominal organs were infiltrated with a poorly demarcated, soft, tan tissue. Microscopically this tissue was composed of neoplastic cells assuming two distinct growth characteristics consistent with Antoni A and B patterns. Ultrastructurally, the neoplastic cells were pleomorphic, lacked junctional devices, had abundant mitochondria and ergastoplasm, and frequently were closely associated with extracellular collagen. Immunocytochemical examination of tumor cells demonstrated sporadic expression of neuron specific enolase. Microscopic tumor metastases to the myocardium, ascending aorta, lungs and visceral pleura were present. This is the first report of a sarcoma compatible with a malignant peripheral nerve sheath tumor in a muskrat.

Angiomatoid (malignant) fibrous histiocytoma as a second tumour in a child with neuroblastoma.

Neuroblastoma occurring as a disseminated disease in children has a poor prognosis. Haematogenous metastases usually involve the marrow, bone, liver and skin. A second neoplasm may also develop. We describe a child with retroperitoneal neuroblastoma (stage 3) who developed a nodular mass in the inguinal area which was suspected to be a metastasis. Histopathology disclosed an angiomatoid (malignant) fibrous histiocytoma, and excision was curative. The occurrence of angiomatoid (malignant) fibrous histiocytoma as a second tumour in a patient with neuroblastoma has not previously been reported.

Desmoplastic small round cell tumor: II: an ultrastructural and immunohistochemical study with emphasis on new immunohistochemical markers.

In order to investigate the histogenesis and facilitate the diagnosis of desmoplastic small round cell tumor (DSRCT), 39 cases were studied by immunohistochemical methods using a large battery of antibodies directed against a wide variety of epithelial, mesenchymal, and neural-associated proteins. Sixteen of these tumors were also studied by electron microscopy. Thirty-seven of 39 cases reacted for cytokeratin using a "cocktail" of 3 monoclonal antibodies (CAM 5.2/AE1/AE3), 39/39 for desmin, 24/25 for epithelial membrane antigen, 22/27 for vimentin, 18/25 for neuron-specific enolase, 10/15 for CD57 (Leu-7), 3/19 for synaptophysin, 1/22 for chromogranin, 3/19 for muscle-specific actin, 3/16 for alpha-smooth-muscle actin, 11/16 for CD15 (Leu-M1), 5/12 for CA-125, 6/17 for CD99, 9/10 for MOC-31, 2/6 for NB84, 5/7 for Ber-EP4, and 8/9 for the Wilms tumor (WT1) protein. No staining was obtained in any of the cases tested for cytokeratin 5/6 or 20, neurofilament proteins, glial fibrillary acidic protein, peripherin, CA19-9, thrombomodulin, alphafetoprotein, carcinoembryonic antigen, TAG-72 (B72.3), placental alkaline phosphatase, S-100 protein, HMB-45, myoglobin, or for the two myogenic regulatory proteins myogenin and MyoD1. A frequent ultrastructural finding was the presence of juxtanuclear aggregates of intermediate filaments, but microfilaments with densities or Z-band-like material suggestive of either smooth or skeletal muscle differentiation were not seen in any case. Dendritic-like processes containing microtubules and dense core granules were seen in four tumors and all of these tumors reacted for at least one of the neural markers investigated. Although ultrastructural and immunohistochemical studies confirmed previous observations that DSRCTs present epithelial, mesenchymal, and neural phenotypes, a great variation was found in the frequency of expression of the different markers used to demonstrate each line of cell differentiation. The absence of expression of cytokeratin 5/6 and thrombomodulin together with positive staining for CD15, MOC-31, and Ber-EP4 argues against the possible mesothelial origin that has been suggested for this tumor. Additionally since none of the tumors reacted for myogenin or MyoD1, desmin expression in DSRCT cannot be regarded as evidence of skeletal muscle differentiation. Although the histogenesis of DSRCT remains unknown, it is believed that this tumor originates from a progenitor cell with potential for multiphenotypic differentiation.

Intraabdominal lymphangiosarcoma in a Fischer-344 rat.

A Sarcoma arising in the abdominal cavity in an aged Fischer-344 rat was studied by immunohistochemistry and electron microscopy. The white-yellow soft mass was located on the lumbosacral vertebrae, compressing adjacent parenchymal organs. The tumor was made up of spindle shaped cells situated in a background of myxoid substance and a small amount of reticulin and collagen fibers. The tumor cells grew in a loose storiform pattern and often adhered to each other by their cell processes to form ovoid or slitlike spaces. Immunohistochemically, the tumor cells were strongly positive for vimentin but negative for keratin, macrophage ED1 antigen, alpha-smooth muscle actin, Factor VIII-related antigen, and S100 protein. Electron microscopy demonstrated the endothelial differentiation of the tumor cells, such as occasional luminal spaces, a small number of micropinocytotic vesicles, and interdigitating junctions with desmosomes between cell processes of adjacent cells. Furthermore, its endothelial origin was suggested by the presence of electron-dense rods resembling Weibel-Palade bodies. Instead of a definitive basement lamina surrounding the tumor cells, there were extracellular thin "anchoring filaments" that were attached to the cell surface at areas of increased electron density. These findings indicate that the tumor is of lymphatic vessel type rather than blood vessel type.

An intra-abdominal small round cell neoplasm with features of primitive neuroectodermal and desmoplastic round cell tumor and a EWS/FLI-1 fusion transcript.

We report an intra-abdominal round cell tumor in a young man which exhibited the light and electron microscopic appearance of a peripheral primitive neuroectodermal tumor (PNET), in addition to the clinical and topographic characteristics, desmoplasia and a complex immunophenotypic profile of the intra-abdominal desmoplastic round cell tumor (DSRCT). Reverse transcription polymerase chain reaction revealed a EWS/FLI-1 fusion transcript as in PNET/Ewing's sarcoma, instead of the EWS/WT1 transcript of DSRCT. The tumor was also strongly positive for the mic2 protein. This is a unique case of a hybrid tumor arising in the peritoneal cavity of a young male. The existence of such a hybrid tumor in this location suggests that DSRCT and PNET may be related and possibly share a common histogenesis.

Desmoplastic small round cell tumor.

Desmoplastic small round cell tumor is an undifferentiated tumor associated with serosal surfaces, especially the peritoneum. It is found predominantly in adolescents and young adults and is much more common in males than in females. The tumor has a characteristic histology, with extensive stromal tissue around islands of small and undifferentiated cells revealing the desmoplastic appearance. The coexpression of epithelial and mesenchymal antigens distinguishes this entity from other small round and blue cell tumors of this age group. Cytogenetic studies showed a t(11;22) translocation that differs from the Ewing's tumor translocation and seems to be specific to this entity. The involvement of the WT1 and EWS genes in the translocation makes this tumor an interesting subject for research on histogenesis and differentiation in small round and blue cell tumors.