Myxoid dermatofibrosarcoma protuberans: morphological, ultrastructural and immunohistochemical features

Two uncommon cases of dermatofibrosarcoma protuberans with prominent myxoid changes are presented. The tumors appeared as large multinodular cutaneous plaques that arose at the sites of excision of previous tumors some years earlier. In addition to limited fibrous storiform features, focally observed in deep and peripheral portions of the tumors, a diffuse myxoid pattern could be observed. The latter consisted of homogeneous areas of rare, stellate or spindle-shaped cells, haphazardly scattered in abundant myxoid matrix. Cells of myxoid neoplastic tissue showed mainly a positive immunoreaction for fibrohistocytic markers and the absence either of muscular, neural or human progenitor cell antigens. Mitotic figures were fewer and cell proliferation rates were lower in myxoid as compared to those of typical dermatofibrosarcoma protuberans used as a control. The ultrastructural examination of myxoid areas revealed a prevalent fibroblast-like cell population showing dilated cytoplasmic vesicles, sometimes containing glycosaminoglycans-like substances. The extent of myxoid changes together with the characteristic morphological, ultrastructural and immunohistochemical features confirm that myxoid dermatofibrosarcoma protuberans is a distinct variant of this fibrohistiocytic tumor to be considered in the differential diagnosis among myxoid tumors of the skin.     

Rhabdomyoma of the tunica vaginalis of the testis: a histologic, immunohistochemical, and ultrastructural study

A case of an unusual tumor of skeletal muscle origin is described. The tumor was located in the tunica vaginalis of the testis in a 19-year-old man. Histologic examination showed a proliferation of elongated or round cells, with clearly discernible cross striations, surrounded by abundant mature connective tissue, consistent with genital rhabdomyoma. Immunohistochemical and electron microscopic features supported this diagnosis. Rhabdomyoma must be considered in the differential diagnosis of paratesticular tumors.     

Gonadoblastoma: histologic, ultrastructural, and histochemical observations in five cases

In this series of gonadoblastomas it appeared that the germ cells were the motivating force underlying either tumor proliferation or regression. The ultrastructural morphology confirmed the presence of undifferentiated gonadal cells with active steroid synthesis by the interstitial cells. The Call-Exner-like bodies which showed extensive calcification were composed of basement membrane material containing a sulfated mucosubstance. A histochemical comparison with the noncalcifying Call-Exner bodies of a granulosa-cell tumor differed only in their glycoprotein content. The calcium deposits were identified as oriented hydroxyapatite crystals by electron diffraction, and it is proposed that the basement membrane material serves as a nucleation site for calcification. High serum testosterone levels were correlated with the presence solely of interstitial cells in one case. The finding of a gonadoblastoma without the presence of a Y chromosome contradicts earlier proposals concerning the requirement of a Y chromosome for germ cell proliferation.     

Malignant rhabdoid tumor of the small intestine in an adult: a case report with immunohistochemical and ultrastructural findings

The expression of platelet-derived endothelial cell growth factor (PD-ECGF) was determined immunohistochemically in 143 non-small cell lung carcinomas. Staining was observed in 48% of the cases. A relationship between histology, stage, erbB-1, erbB-2, ras and PD-ECGF expression was not found. A relationship of borderline significance was observed between PD-ECGF and p53 expression. There was also no relationship between PD-ECGF expression and proliferative activity (G1 phases, S phases, cyclin A). In contrast, a correlation between PD-ECGF- and VEGF-expression was detectable (p=0.009). Furthermore, PD-ECGF expression was related to the response of lung carcinomas to doxorubicin (p=0.0004). Of 35 sensitive tumors, 26 carcinomas were PD-ECGF-positive (74%) while of 108 resistant carcinomas only 43 tumors (40%) exhibited PD-ECGF expression.     

p53 in node-negative breast carcinoma: an immunohistochemical study of epidemiologic risk factors, histologic features, and prognosis

PURPOSE: The present study explores p53 in relation to the following four aspects of node-negative breast carcinoma: epidemiologic risk factors, tumor histopathology, prognosis, and HER2/neu (HER) expression. MATERIALS AND METHODS: Immunohistochemical (IH) staining for p53 was performed on formaldehyde-fixed, paraffin-embedded primary invasive carcinomas from 440 node-negative patients with a median follow-up duration of 119 months. RESULTS: The IH expression, or lack thereof, of p53 separately or in combination with HER did not prove to be prognostically significant and there was no consistent association of p53 with epidemiologic risk factors. p53 was expressed in 68% of medullary carcinomas (MEDs), which is a significantly higher frequency (P < .001) than in lobular (9%) and duct (23%) carcinomas. p53 was not found in some types of low-grade carcinomas (tubular and papillary), and was observed in a minority of mucinous carcinomas. p53 was present significantly more often in carcinomas with high-grade or poorly differentiated nuclear grade than in low- or intermediate-grade tumors. There was an inverse statistically significant relationship between estrogen receptor (ER) positivity and p53 expression. Tumors with the p53(+)/HER(-) immunophenotype tended to be MEDs or duct carcinomas with a marked lymphoplasmacytic reaction. Infiltrating lobular carcinomas (IFLCs) were largely p53(-)/HER(-). p53(+)/HER(+) carcinomas had the best prognosis. The poorest outcome was associated with the p53(-)/HER(+) immunophenotype. This trend was statistically significant for recurrence-free and overall survival in patients with T1NOMO infiltrating duct carcinoma (IFDC). CONCLUSION: The IH demonstration of p53 was not a reliable prognostic indicator in the node-negative breast carcinoma patients studied and it was not associated with major epidemiologic risk factors. The combined immunophenotypic expression of p53 and HER was significantly associated with some histologic types of breast carcinoma and with prognosis in T1NOMO breast carcinoma.     

Secretory meningioma: clinical, histologic, and immunohistochemical findings in 31 cases

BACKGROUND: Secretory meningioma is a rare histologic variant characterized by a unique epithelial differentiation of meningothelial cells resulting in the production of hyaline inclusions. Most previous reports have presented single case observations. The authors selected 31 cases for a clinicopathologic study to characterize this type of tumor further. METHODS: Clinical data were compiled and the extent of peritumoral edema was assessed from preoperative computed tomography or magnetic resonance imaging scans. Preparations of surgical specimens of all tumors were studied after both conventional histologic and immunohistochemical preparations were made. Immunostaining was performed by either the avidin-biotin complex method or the alkaline phosphatase-antialkaline phosphatase method using 22 primary antibodies. RESULTS: In the tumor collection used in this study, secretory meningiomas represented 3% of meningiomas. The female-to-male ratio was 9:1. Most tumors were located at the sphenoid ridge or at the frontal convexity, and recurrences were not observed. Eighty-four percent of tumors presented with slight to marked peritumoral edema. The MIB-1 staining index showed a mean of 3.8%. Inclusions and surrounding cells consistently expressed epithelial membrane antigen, cytokeratins, carcinoembryonic antigen, and carbohydrate antigen 19-9. In decreasing frequency, they also contained alpha1-antitrypsin, immunoglobulin (Ig)A, alpha1-antichymotrypsin, IgM, and IgG. Cells positive for vimentin and S-100 did not contain inclusions. All tumors were positive for progesterone receptors. Macrophages were stained with antibodies to factor XIIIa, human leukocyte antigen-DR, and alpha1-antitrypsin. In 64% of cases, tumor vessels lacked expression of glucose transporter protein 1. CONCLUSIONS: The classification of secretory meningioma as a distinct variant has been justified on clinical, histologic, and immunohistochemical grounds. The unique epithelial features call attention to the broad spectrum of differentiation properties found in meningiomas.     

Pathomorphologic characteristics and differential diagnosis of small hepatocellular carcinoma

Recent advances in various diagnostic imagings have made possible early diagnosis of hepatocellular carcinoma (HCC). Grossly, small HCCs of the early stage up to around 1.5 cm in diameter are vaguely demarcated from surrounding liver tissue. Such minute tumors are classified as small HCC with indistinct margins. Histologically, these tumors consist of uniform distribution of well-differentiated cancerous tissues, which are characterized by increased cell density with increased nuclear/cytoplasmic ratio, irregular thin-trabecular pattern with occasional pseudoglandular structure, and frequent fatty and/or clear cell change. In all small HCCs with indistinct margins, varying numbers of portal tracts are contained within the cancerous tissues. None of them represents invasion of the portal vein or intrahepatic metastasis. Thus, small HCC with indistinct margins is considered to be HCC of the earliest stage that can be clinically detected at this moment. Along with the increase of resected small HCCs, hyperplastic lesions such as adenomatous hyperplasia (AH) and atypical AH, which are difficult to differentiate from well-differentiated HCC have also been found. Atypical AH is considered a borderline malignancy. Some focal nodular hyperplasias and liver cell adenomas are also difficult to differentiate from well-differentiated HCC. It should be recalled that some metastatic tumors such as carcinoid tumor, renal cell carcinoma and hepatoid adenocarcinoma also resemble HCC.     

Subependymal giant cell astrocytoma: clinical, histologic and immunohistochemical characteristic of 3 cases

The role of 5-hydroxytryptamine (5-HT) in neural reflexes regulating secretion was examined in muscle-stripped segments of guinea-pig colon set up in modified flux chambers. A 15-microL pulse of 5-HT (100 microM) to the mucosal bath (1.5 mL), which was continuously perfused, evoked an increase in short-circuit current (Isc). The 5-HT-induced increase in Isc was inhibited by tetrodotoxin, N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide (5-HTP-DP), GR82334 and atropine, but not by tropisetron. 5-HTP-DP reduced the response to a 5-HT pulse over the concentration range of 1 nM to 1 microM. The Isc response to a 5-HT pulse was unaffected by the cyclooxygenase inhibitor, piroxicam. This contrasted with a reduction in the Isc response to mucosal stroking with a brush by piroxicam. The results suggest that a 5-HT pulse, like mucosal stroking, activates a secretory reflex that includes tachykinin and cholinergic neurons but, unlike mucosal stroking, does not release prostaglandins.     

Mucoepidermoid carcinoma arising in Warthin''s tumour of the parotid gland: report of two cases with histopathological, ultrastructural and immunohistochemical studies

OBJECTIVE: To study the molecular defects of congenital adrenal hyperplasia (CAH). STUDY DESIGN: Twenty Chinese patients, including 8 with salt-wasting (SW) type CAH, 11 with simple virilizing (SV) type CAH and 1 with nonclassical (NC) type CAH, were recruited. Two rounds of the polymerase chain reaction (PCR) were used to study the 21-hydroxylase gene (CYP21). The primary PCR amplified CYP21-specific DNA fragments, and the secondary PCR used products from the primary PCR for analysis of amplification-created restriction sites (ACRS) and direct DNA sequencing. In all patients, ACRS analysis was done at 12 possible mutation sites, and then direct DNA sequencing was performed to confirm or define the molecular defects. RESULTS: Ten different mutations, including nine point mutations and gross gene deletion or conversion, were found in this study. Of the nine point mutations, eight could be easily detected by ACRS analysis. The three most common mutations were codon (CD)172 t-->a (I172N), IVS-II 656 c/a-->g, and gross gene deletion or conversion, accounting for 27.5% (11/40 alleles), 25% (10/40) and 20% (8/40) of all identified mutations, respectively. All SW patients were compound heterozygotes of IVS-II 656, gross gene deletion or conversion, or other severe defects, including CDs236 (t-->a) (I236N)+ 237 (t-->a) (V237E)+ 239 (t-->a) (M239K), CD306 (+t), CD318 (c-->t) (Q318X) and CD356 (c-->t) (R356W) mutations. All SV patients had one allele with a CD172 (I172N) mutation. One allele of an NC patient had a CD183 (c-->g) (D183E) mutation, and the other allele was not defined. In the whole series, four alleles (10%) had more than one mutation. CONCLUSION: We found 10 different mutations in this study. The correlation between genotypes and phenotypes was compatible with the reported data. Two rounds of PCR and ACRS analysis may provide important information for genetic counseling, prenatal diagnosis and management of families at risk for CAH.     

Synovial hemangioma: imaging features in eight histologically proven cases, review of the literature, and differential diagnosis

OBJECTIVE: This study was undertaken to describe the imaging characteristics of synovial hemangioma, with the goal of improving the disappointing rate (22%) of clinical diagnosis of this condition. A review of the literature and the differential diagnosis of intra-articular lesions, including synovial osteochondromatosis and pigmented villonodular synovitis, are also presented. PATIENTS: The subjects of the study were 8 patients (4 males, 4 females; age range: 5-47 years; mean age: 19 years) with histologically confirmed synovial hemangioma involving the knee (n = 7) or wrist (n = 1). We retrospectively examined the imaging studies performed in these patients, including plain radiography (n = 8), magnetic resonance imaging (MRI; n = 4), angiography (n = 3), arthrography (n = 2), and contrast-enhanced computed tomography (CT; n = 2). RESULTS: Plain radiographs showed a soft tissue density suggesting either joint effusion or a mass in all patients. Phleboliths and bone erosions on plain films in four patients with extra-articular soft tissue involvement pointed to the correct diagnosis. Angiography, showing fine-caliber, smooth-walled vessels, contrast pooling in dilated vascular spaces, and early visualization of venous structures, was diagnostic in two patients. Neither arthrography nor CT yielded specific enough findings. MRI was consistently effective in allowing the correct diagnosis to be made preoperatively, showing an intra-articular or juxta-articular mass of intermediate signal intensity on T1-weighted images and of high signal intensity of T2- or T2*-weighted images with low-signal channels or septa within it. A fluid-fluid level was found in two patients with a cavernous-type lesion. CONCLUSION: Despite the limited nature of this study, it shows clearly that MRI is the procedure of choice whenever an intra-articular vascular lesion such as synovial hemangioma is suspected. Nonetheless, phleboliths and evidence of extra-articular extension of plain radiographs point to angiography as an effective procedure of first resort because it can be combined with embolotherapy.     

Hepatic leiomyosarcoma: ultrastructural study and review of the differential diagnosis

A primary leiomyosarcoma of the liver in a 12 year old female is reported. It is the eleventh such tumor to be recorded, the first to be documented in an adolescent and the first to be studied electron microscopically. By light microscopy the well differentiated portions of the tumor were characteristic of leiomyosarcoma. Ultrastructurally a minority of tumor cells contained myofilaments along with cytoplasmic dense bodies and marginal dense plaques, the most distinctive subcellular markers of smooth muscle cells. A brief review of the differential diagnosis is provided.     

Primary renal angiosarcoma: a case report with immunohistochemical, ultrastructural, and cytogenetic features and review of the literature

Primary angiosarcoma of the kidney is a rare tumor for which fewer than 10 case reports appear in the English literature. A case of primary renal angiosarcoma is reported, in which the tumor showed poorly differentiated spindled sarcoma admixed with typical angiomatous differentiation. Antibodies against CD31, CD34, Ulex europeus lectin type I, factor VIII-related antigen, cytokeratin (AE1/AE3), vimentin, S100 protein, epithelial membrane antigen, carcinoembryonic antigen, desmin, and smooth muscle actin were examined. CD31 showed strong diffuse membranous staining of cells in the well-differentiated areas and strong membranous staining in the spindled, poorly differentiated areas. CD34 showed strong cytoplasmic and membranous staining in both the poorly differentiated and well-differentiated areas. Staining for factor VIII-related antigen and Ulex europeus was less intense and was limited to the well-differentiated areas. Staining for cytokeratin (AE1-AE3), S100, carcinoembryonic antigen, epithelial membrane antigen, desmin, and smooth muscle actin were negative. Electron microscopy showed spindle cells containing abundant pinocytotic vesicles, vimentin-type intermediate filaments, and rare Weibel-Palade bodies. A complex karyotype was found. Our findings suggest that CD31 and CD34 are useful in defining endothelial differentiation in poorly differentiated angiosarcomas in which reactions for Ulex europeus lectin type I and factor VIII-related antigen may be equivocal.     

Chromophobe renal cell carcinoma. Pathologic, ultrastructural, immunohistochemical, cytofluorometric and cytogenetic findings

A case of chromophobe renal cell carcinoma is reported in a 73 year-old man. Light microscopically, the tumor was composed of polygonal cells with a slightly eosinophilic and a fine reticular pattern, and a reaction of the cytoplasm with Hale's acid iron colloid. Ultrastructural analysis showed membranous microvesicles within the tumor cells, with degenerated mitochondria. Immunohistochemical profile against intermediate filaments was positive to cytokeratin 18 and negative against vimentin. Flow cytometry and cytogenetics revealed a predominant hypertriploid population. Few cases have been published with flow cytometry and cytogenetic findings. We report a new case.     

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

The clinical and histological features of 39 cases of desmoplastic small round cell tumor (DSRCT) diagnosed at M.D. Anderson Cancer Center are presented. Thirty-two of the patients were men and seven were women ranging in age from 10 to 41 years (mean, 25 years). Twenty-five of the 35 patients for whom follow-up information was available died of widespread metastases 8 to 50 months (mean, 25.2 months) from the time of their diagnosis and the remaining 10 were alive with disease. With the exception of two cases that occurred in the liver and in the scrotum, respectively, all of the cases originated within the abdominal and/or pelvic peritoneum. Eight tumors also involved the retroperitoneum. Although the characteristic histologic pattern of "small, blue cells" embedded in a dense fibrous stroma was seen in most cases, about one third of the tumors exhibited a wide range of morphologic features. The recognition of these uncommon morphologic variants of DSRCT is of paramount importance to avoid a misdiagnosis because these tumors could potentially be confused with other neoplastic conditions.     

Laryngeal sarcomatoid carcinoma: clinical, histological and immunohistochemical study of four cases

A 1488-bp fragment of bovine retina guanylate cyclase B gene encoding the catalytic and dimerizing domains as well as part of the protein kinase domain was expressed in Escherichia coli cells. The expression product was obtained as inclusion bodies and solubilized in 6 M guanidine hydrochloride. The fragment of guanylate cyclase B is a dimer close in catalytic activity to the native enzyme.     

Chordomas of the mediastinum: clinicopathologic, immunohistochemical, and ultrastructural study of six cases presenting as posterior mediastinal masses

Six cases of chordomas presenting as primary posterior mediastinal tumors are described. Three patients were female, and three were male between the ages of 8 and 65 years (mean, 40.6 years). In all cases, the tumors presented radiographically as relatively well-circumscribed, encapsulated soft tissue masses that did not seem to be related to the thoracic or dorsal spine. Only in one case, focal infiltration of bone at the level of T6-T7 was observed at the time of surgery. Histologically, the lesions showed a spectrum of features that ranged from sheets and cords of large cells with abundant vacuolated cytoplasm to small, stellate cells embedded within an abundant mucoid matrix. In one case, the cell population showed more pronounced nuclear atypia with loss of cytoplasmic vacuolization, frequent mitotic figures, necrosis, and solid areas characterized by a perivascular distribution of atypical spindle cells set against a myxoid stroma. Another case showed features of chondroid chordoma, with an immature chondroid-appearing matrix surrounding the atypical tumor cells. Immunohistochemical studies in all cases showed positive staining of the tumor cells with CAM 5.2 and broad-spectrum keratin, epithelial membrane antigen (EMA) and vimentin, and, to a lesser extent, with S-100 protein. Stains for muscle actin, carcinoembryonic antigen (CEA), and desmin were negative. Ultrastructural examination in two cases showed a spectrum of features that varied from large cells with abundant cytoplasm containing scattered ribosomes, glycogen granules, Golgi apparatti, abundant intermediate filaments, and small lumen formation with immature microvilli to smaller cells with elongated cytoplasmic processes, fewer intermediate filaments, rare desmosome type intercellular junctions, and complexes of mitochondria/rough endoplasmic reticulum. On clinical follow-up, two patients died with metastases to the lungs, chest wall, and liver from 1 to 3 years after diagnosis, and two patients are alive and well without evidence of disease after 3 and 16 years. Chordoma should be entertained in the differential diagnosis of posterior mediastinal tumors. Application of immunohistochemical stains or electron microscopy will be of aid in separating them from other conditions that may histologically closely resemble these lesions.     

Cytodifferentiation of atypical adenomatous hyperplasia and bronchioloalveolar lung carcinoma: immunohistochemical and ultrastructural studies

We used immunohistochemistry and electron microscopy to evaluate the differentiation of cells comprising atypical adenomatous hyperplasia (AAH; n = 26), early bronchioloalveolar lung carcinoma (BAC; n = 11), and overt BAC (n = 16), which are assumed to constitute a continuous spectrum of developmental steps of BAC. Surfactant apoprotein (SAP), a marker for type 2 alveolar cells, was expressed in cells from all the lesions of AAH, early BAC, and overt BAC. However, the proportion of SAP-positive cells decreased and their distribution became more heterogeneous with advancing lesion grade. Urine protein 1, which is identical to the Clara cell-specific 10 kDa protein, was expressed in 70% of overt BAC, whereas only 20% of early BAC showed weak reactivity and none of AAH lesions showed any reactivity at all. Ultrastructurally, type 2 alveolar cell differentiation was predominant among cells from AAH and early BAC. Our results suggest that precursor cells of BAC differentiate predominantly towards type 2 alveolar cells. Cells comprising overt BAC retain this differentiation phenotype, but to a reduced extent. In contrast, concomitantly with progression, cells with Clara cell differentiation emerge and their proportion increases. Such phenotypic changes may reflect metaplasia occurring in tumour cells during the development of BAC.     

Medullary carcinoma of the thyroid: histomorphological, histochemical and immunohistochemical analysis of twenty cases

Histomorphological patterns of twenty primary medullary carcinomas of the thyroid were studied by light and polarized microscopy in relation to the content of calcitonin and thyroglobulin determined by the immunoperoxidase method: Out of 20 tumors, 10 showed classical, 7 glandular and 3 insular histomorphological pattern. In 19/20 cases, the cytoplasm of tumor cells contained various amounts of calcitonin, and the intensity of Immunoreaction was strong in 2/19, moderate in 7/19 and weak in 10/19 cases. Tumor stroma contained calcitonin in 7/20 cases. In 1/20 case, which did not show calcitonin immunoreactivity in the cell cytoplasm, the stroma contained a considerable amount of calcitonin. Thyroglobulin immunoreactivity was found in 4/20 tumors, 2 of them with classic and 2 with glandular histomorphological picture only in the cytoplasm of tumor cells. These tumors are considered medullary carcinomas with thyroglobulin immunoreactivity, since they do not fulfil the WHO criteria for "mixed medullary-follicular carcinomas".     

Thyroid paraganglioma: a clinicopathologic and immunohistochemical study of three cases

We report three cases of intrathyroidal paraganglioma. The patients were adult women without significant personal or family histories that presented with an asymptomatic thyroid nodule. The tumors were single, well-circumscribed solid masses, 2 cm in greatest diameter, located within one thyroid lobe. Microscopically, they were encapsulated and showed the typical nesting (Zellballen) pattern of paraganglioma in other sites. Two of the tumors were composed of small- to medium-sized cells with granular amphophilic cytoplasm, and the third consisted of relatively large cells having a similar staining quality. Immunohistochemically, all tumors showed positivity for neuron-specific enolase, chromogranin A, and synaptophysin. S-100 protein-positive sustentacular cells were demonstrated in each case. Negative staining for epithelial markers, thyroglobulin, carcinoembryonic antigen, calcitonin, calcitonin gene-related peptide, serotonin, vimentin, and Congo red excluded other tumors that were considered in the differential diagnosis, such as medullary carcinoma, hyalinizing trabecular adenoma, atypical follicular adenoma, Hurthle-cell neoplasm, and metastatic carcinoid tumor. The patients were alive and well without evidence of recurrent disease at the time of the last follow-up. The previous literature on these tumors is discussed. We conclude that intrathyroidal paraganglioma exists and that this tumor can be distinguished from other similar-appearing neoplasms in this organ.     

Primary heterologous carcinosarcoma (metaplastic carcinoma) of the urinary bladder: a clinicopathologic, immunohistochemical, and ultrastructural analysis of eight cases and a review of the literature

BACKGROUND: Heterologous carcinosarcomas of the urinary bladder are rare neoplasms, the histogenesis of which is still disputed. METHODS: The clinicopathologic, immunohistochemical, and ultrastructural features of eight cases were analyzed. RESULTS: The patients, 5 males and 3 females, had a median age of 70 years. Gross hematuria, dysuria, and urinary tract infections were the main presenting symptoms. Tumors were solitary in all cases and located in the right wall in six cases. Tumor size ranged from 2 to 12 cm (median, 5 cm). Four patients died of disease 2, 6, 17, and 42 months postoperatively, respectively. Microscopically, the tumors consisted mostly of a varied mixture of high grade transitional cell carcinoma with chondrosarcoma, osteosarcoma, rhabdomyosarcoma, and undifferentiated spindle cell (leiomyosarcoma-like) components with occasional transitional features between one component and another. All tumors but one invaded the muscularis propria or the perivesical fatty tissue. Immunohistochemically, keratin expression was observed focally in the sarcoma component as well as the carcinoma component. Reactivity for vimentin, desmin, muscle specific actin, and S-100 protein was observed in poorly differentiated areas in addition to the expected positivity of each histologic subtype of sarcoma. Ultrastructurally, one tumor showed evidence of both epithelial and chondrosarcomatous differentiation, whereas three contained rhabdomyosarcomatous elements. CONCLUSIONS: On the basis of the current series and a review of 55 reports from the literature, primary heterologous carcinosarcoma of the urinary bladder proved to be a highly malignant type of neoplasm occurring predominantly in elderly males that was most often in an advanced stage at presentation and rapidly became lethal. Histogenetically, some heterologous carcinosarcomas should be regarded as a variant of sarcomatoid carcinoma (metaplastic carcinoma) that shows prominent heterologous differentiation.