SAS amplification in soft tissue sarcomas.

Gene amplification is an important mechanism of increased gene expression in a number of human solid tumors. We have recently identified and cloned sequences from a novel DNA amplification unit in malignant fibrous histiocytoma. The amplified sequences are derived from chromosome 12q13-14 and encode a gene designated SAS (sarcoma amplified sequence). In the present study, a series of soft tissue sarcomas was studied to characterize further the phenomenon of SAS amplification. Seven of 22 (32%) malignant fibrous histiocytomas and three liposarcomas contained SAS amplification. Strikingly, all of the tumors with SAS amplification occurred in central sites (i.e., in the abdominal or inguinal regions) rather than in the extremities (i.e., in the arms of legs). These observations demonstrate that SAS amplification occurs with a significant frequency in mesenchymal tumors and is particularly associated with abdominal disease.

Immunohistochemical localization of metabotropic glutamate receptors mGluR1a and mGluR2/3 in the rat basal ganglia.

Metabotropic glutamate receptors (mGluRs), which couple glutamate to second messengers, have important roles in the regulation of movement by the basal ganglia. We used two polyclonal antisera to mGluR1a and mGluR2/3 and confocal laser microscopy to investigate the localization of these receptors in the basal ganglia of the rat. The mGluRs were visualized in combination with an antibody to tyrosine hydroxylase (TH), an antibody to microtubule-associated protein 2 (MAP2, a dendritic marker), or SV2 (an antibody to a protein associated with presynaptic terminals). In the neostriatum, punctate mGluR1a immunoreactivity (ir) was present in the neuropil. This staining did not colocalize with MAP2-ir or SV2-ir and was not altered by decortication or unilateral 6-hydroxydopamine (6-OHDA) lesions. In the globus pallidus and substantia nigra pars reticulata, however, mGluR1a-ir was tightly clustered along large MAP2-ir dendrites. In contrast to the variations in mGluR1a-ir staining, similar punctate neuropil mGluR2/3-ir staining was observed within all basal ganglia structures. In the neostriatum, these puncta were abundant; unlike mGluR1a, many mGluR2/3-ir puncta colocalized with SV2-ir, and striatal mGluR2/3-ir puncta were markedly reduced in number after decortication. Neither mGluR1a-ir nor mGluR2/3-ir could be detected in TH-ir soma within substantia nigra pars compacta, or in TH-ir striatal terminals. Overall, our observations suggest that mGluR1a and mGluR2/3 receptors have distinct cellular localizations in different components of the basal ganglia circuitry and are likely to subserve distinct functions. Our data support the presence of mGluR2/3 on the terminals of corticostriatal afferents, where they may regulate glutamate release. In contrast, mGluR1a appears to be a postsynaptic receptor of neurons in the neostriatum, globus pallidus, and substantia nigra pars reticulata.

Proliferative fibroblastic lesions. From hyperplasia to neoplasia.

It is rare to find a pathologist whose ideas and beliefs are so sound and pervasive as to influence our thinking decades after his writing. Yet such was the case with Dr. Stout, to whom we owe our basic classification of fibroblastic tumors, our concept of fibromatosis, and our diagnostic approach to fibrosarcomas. We need to continue the progress Dr. Stout made in these areas and to search for biochemical and molecular differences in these tumors with the hope that this knowledge will lead to new avenues for therapy.

Multicystic mesothelioma. An analysis of pathologic findings and biologic behavior in 37 cases.

We report the clinicopathologic findings of 37 cases of multicystic mesothelioma. The tumor, which occurs most frequently in young to middle-aged women, affects chiefly the pelvic peritoneum--particularly the cul de sac, uterus, and rectum. It grows along the serosa as multiple, translucent, fluid-filled cysts. Occasionally, it manifests as a solitary or free-floating mass. The tumor is made up of mesothelial-lined cysts embedded in a delicate fibrovascular stroma. The mesothelial cells may be flattened or cuboidal. Adenomatoid change or squamous metaplasia of the mesothelium occurs in one-third of cases. In a significant percentage of cases, the stroma shows marked inflammatory changes that make it difficult to recognize the underlying neoplastic nature. Follow-up information in 25 patients showed that 21 patients were alive, two had died of tumor, and two died of other causes. One of the two patients who died of their tumors was an infant whose tumor showed transition to conventional mesothelioma; the other was a man who had refused therapy. The extent of tumor at the time of diagnosis did not predict survival. The low incidence of previous surgery, the lack of prior abdominal infections, and the documentation of disease-related mortality all support a neoplastic, rather than a reactive, basis for this lesion.

Angiomatoid malignant fibrous histiocytoma. A follow-up study of 108 cases with evaluation of possible histologic predictors of outcome.

Described by Enzinger in 1979, angiomatoid malignant fibrous histiocytoma is a distinctive tumor of adolescence and early adult life characterized by sheets of relatively bland rounded or spindled cells separated by areas of cystic hemorrhage and surrounded by a prominent inflammatory infiltrate and often a fibrous pseudocapsule. On the basis of the original 41 cases, the tumor has been considered a low-grade malignancy. We are reporting the clinicopathologic findings and follow-up information of 108 new cases of angiomatoid malignant fibrous histiocytoma to determine the long-term behavior of this tumor and whether various histologic features (atypia, mitoses, infiltrative borders, and inflammatory infiltrate) are useful in predicting outcome. Follow-up information was obtained in 94 (87%) cases. Local recurrences developed in 11 patients (12%), all of whom were cured by re-excision. The initial excision in all patients developing local recurrence appeared to be incomplete. Local recurrence was statistically associated with irregular tumor border and head and neck location. Five patients developed metastases. Four had only local metastases, which responded to surgery, whereas the fifth patient developed presumed pulmonary and cerebral metastases and died. The development of both local and distant metastases was correlated with invasion into the deep fascia or muscle but not to various histologic parameters such as mitotic rate and pleomorphism. We conclude that angiomatoid malignant fibrous histiocytoma is intrinsically a low-grade tumor, and assessment of various histologic parameters or grading provides little or no additional prognostic information. Because death from disease occurred in only one patient (1%) in our series, it seems reasonable to reclassify angiomatoid malignant fibrous histiocytoma with fibrohistiocytic tumors of intermediate malignancy rather than with the conventional malignant fibrous histocytoma, the majority of which are high-grade sarcomas.

Angiomatosis of soft tissue. An analysis of the histologic features and clinical outcome in 51 cases.

The clinicopathologic features and clinical behavior of 51 cases of angiomatosis of soft tissue are analyzed. We have defined this lesion as a histologically benign vascular lesion that affects a large segment of the body in a contiguous fashion either by vertically involving multiple tissue types (e.g., subcutis, muscle, bone) or by involving similar tissue types (e.g., multiple muscles). Such lesions usually present in the first two decades of life and have a highly characteristic but not totally specific histologic pattern. The common pattern consists of a haphazard proliferation of vessels of varying sizes, particularly large veins. The latter have irregularly attenuated walls and intimal redundancies. However, the most distinctive feature is the presence of clusters of capillary vessels residing within or just adjacent to the vein walls. A second but uncommon pattern is that of clusters of capillary-sized vessels infiltrating the soft tissues. Both types are typically associated with large amounts of fat, suggesting that these lesions are more generalized mesenchymal proliferations rather than exclusive vascular lesions. This idea is supported by one unique case that included as part of the lesion a diffuse proliferation of glomus cells. Follow-up information in 25 cases (median 5 years; range 1-24) indicated that 22 patients experienced local recurrences. Nine patients developed more than one recurrence. There was no correlation between the age of onset of the lesion and the number of recurrences.(ABSTRACT TRUNCATED AT 250 WORDS)

CD-34 is expressed by a distinctive cell population in peripheral nerve, nerve sheath tumors, and related lesions.

The pattern of CD-34 antigen (human progenitor cell antigen) immunoreactivity was studied within normal nerve, and a variety of nerve sheath and neuroectodermal tumors. Besides normal nerves, 111 soft tissue tumors were studied, including 17 neurofibromas, 10 neurilemomas, 12 malignant peripheral nerve sheath tumors, 1 melanocytic schwannoma, 21 fibroblastic lesions, 31 fibrohistiocytic lesions, seven neuroectodermal lesions, and 10 miscellaneous tumors. CD-34-positive dendritic cells were consistently identified within the endoneurium of normal nerve, all neurofibromas, dermatofibrosarcomas, and Antoni B (but not Antoni A) areas of neurilemomas. CD-34 was not expressed in the majority (eight of 10 cases) of malignant peripheral nerve sheath tumors. CD-34 was also lacking in all fibroblastic lesions (nodular fasciitis, fibromatosis, keloid, fibrosarcoma) and in neuroectodermal tumors that are not generally considered to show true nerve sheath differentiation (neurotropic melanoma, clear cell sarcoma, neuroepithelioma). We conclude that CD-34 (or a closely related epitope) defines a normally occurring nerve sheath cell that appears to be cytologically and immunophenotypically distinct from a fibroblast and conventional Schwann cell. The antigen can also be localized to benign nerve sheath tumors, but tends to be lost in malignant ones. The consistent presence of CD-34 within all 13 cases of dermatofibrosarcoma protuberans can be used as evidence in support of the view that these lesions are variants of nerve sheath tumors, and distinct from benign fibrous histiocytomas which consistently lack the antigen. Finally, expression of CD-34 by one of three giant cell fibroblastomas reinforces the close relationship between this tumor and dermatofibrosarcoma protuberans.

Well-differentiated liposarcoma (atypical lipoma) of deep soft tissue of the extremities, retroperitoneum, and miscellaneous sites. A follow-up study of 92 cases with analysis of the incidence of "dedifferentiation".

Ninety-two cases of well-differentiated liposarcoma of deep soft tissue of the extremity, retroperitoneum, and groin with follow-up information of at least 2 years and no evidence of dedifferentiation at the time of diagnosis were studied to determine their long-term behavior. The tumors occurred most commonly in the muscles of the extremity (46 cases), followed by the retroperitoneum (23 cases), groin (14 cases), and miscellaneous sites (nine cases). Tumors in the retroperitoneum recurred in nearly all cases (21 of 23 cases), occasionally caused patient death, and dedifferentiated in four cases (median time to dedifferentiation, 8 years). Tumors in the groin had a similar high recurrence rate (11 of 14 cases), caused death of patients (two of 14 cases), and dedifferentiated (four of 14 cases). In contrast, those in the extremity recurred less frequently (20 of 46 cases) and had no disease-related mortality. Three of 46, however, underwent dedifferentiation (median time to dedifferentiation, 7 years). Of the 11 cases that underwent dedifferentiation, the interval between diagnosis and dedifferentiation ranged from 2 to 18 years (median time, 9 years; average time, 11 years). Six of the 11 patients showed dedifferentiated foci in the first recurrence, and three died of metastatic disease. Our study indicates that the behavior of well-differentiated liposarcomas is strongly influenced by location. Although the prevailing view is that dedifferentiation is restricted to tumors of the retroperitoneum, our study indicates that it is not a site-specific phenomenon, but is more likely a time-dependent phenomenon seen in situations with a high likelihood for clinical persistence of disease for a long period. Dedifferentiation identifies a tumor that is potentially more aggressive; yet the progression of the disease following dedifferentiation may be highly variable and probably depends on a number of factors, including the amount of dedifferentiation and type of therapy. Although atypical lipoma is an acceptable term for well-differentiated liposarcomas of the subcutis, it fails to convey the potentially life-threatening properties of retroperitoneal tumors. For these lesions as well as those in the deep soft tissues of the extremity, retention of the term well-differentiated liposarcoma is advocated.

Spindle cell hemangioendothelioma. A low-grade angiosarcoma resembling a cavernous hemangioma and Kaposi's sarcoma.

Twenty-six cases of a newly recognized form of vascular tumor are presented. The tumor may occur at any age, has a male predominance, and develops preferentially in the dermis and subcutaneous tissues of the distal extremities. Histologically it combines the features of both a cavernous hemangioma and Kaposi's sarcoma. It is composed of thin-walled cavernous vessels which may be dilated, partially collapsed, or filled with organizing thrombi and phleboliths. These areas are intimately associated with spindled areas reminiscent of Kaposi's sarcoma. The spindled areas differ from Kaposi's sarcoma by the presence of occasional epithelioid endothelial cells, which sometimes display vacuolization. Follow-up information in 14 cases indicates that nine patients experienced "recurrences." One patient, who also received radiotherapy, developed regional lymph node metastasis 40 years after diagnosis and following 19 recurrences. No patient, however, has died of his disease, despite relatively limited surgical excision. The term "spindle cell hemangioendothelioma" is suggested for this vascular tumor of low-grade malignancy.

Massive localized lymphedema in the morbidly obese: a histologically distinct reactive lesion simulating liposarcoma.

We report 14 cases of a soft tissue lesion in the limbs of morbidly obese adults that presents as a large mass and histologically simulates well-differentiated liposarcoma (WDL). Based on its distinctive clinical setting and morphologic identity to diffuse lymphedema we have termed this process massive localized lymphedema (MLL). All cases occurred in morbidly obese adults (mean weight 372 lbs; mean age 47 years). Women predominated (9 women; 5 men). The lesions affected the proximal medial aspect of the extremities (12 thigh; 2 arm) and were unilateral in all but two patients. Etiologically significant antecedent events include ipsilateral axillary lymphadenectomy in both patients with arm lesions, chronic lymphedema resulting from vein-stripping 10 years prior in one patient. inguinal lymphadenectomy for anal carcinoma in another patient, and significant blunt trauma to the inner thigh during a motor vehicle accident in a third patient. The tumors were long standing ( I-IO years) and extremely large (mean size 33.4 cm, 7408 g). Clinically, they were diffuse, ill-defined masses that histologically consisted of lobules of mature fat interrupted by expanded connective tissue septa. The constituents of the septa were fine, fibrillary collagen, edema fluid, and uniformly distributed fibroblasts. Clusters of capillaries were frequently found at the interface between fat and connective tissue. The widened septa simulated the fibrous bands of sclerosing WDL, but MLL lacks the degree of nuclear atypia seen in the former. The consistent clustering of reactive vessels at the interface between the fat and fibrous tissue also contrasted with WDL. Six patients experienced persistent or recurrent lesions within 10 months to 10 years. No aggressive growth or histologic progression was observed during this time, however. Awareness of the features of MLL is important to avoid misclassification of this reactive lesion with WDL.

Spindle cell hemangioendothelioma. An analysis of 78 cases with reassessment of its pathogenesis and biologic behavior.

Seventy-eight cases of spindle cell hemangioendothelioma (SCH) were studied to reevaluate its pathogenesis and determine its long-term behavior. Most of the original findings were confirmed by this study. The tumor occurred at all ages (8-78 years; median, 32 years; mean, 34 years). Males and females were equally affected. The tumor developed as a superficially located mass of the distal extremities (upper, 32 cases; lower, 30 cases). Four patients (5%) also had Maffucci's syndrome. The lesions were circumscribed red-brown masses occasionally containing phleboliths that consisted of cavernous blood spaces alternating with cellular areas consisting of collapsed vascular spaces separated by spindled fibroblastic cells. Often the endothelium lining the collapsed blood spaces appeared epithelioid with cytoplasmic vacuolization. The spindled fibroblastic cells lacked significant atypia and had at most a low level of mitotic activity. As a significant departure from what was originally reported, more than half of these cases (58%) were partially or completely intravascular. The vein containing the tumor often had an irregularly attenuated wall with small intimal herniations and intimal papillae traversing the lumen. Similar intimal changes in adjacent vessels suggest that SCH grows as a multifocal or contiguous process within vessels. Follow-up information was obtained in 40 cases, ranging from 1 month to 40 years (mean, 5.4 years). Despite conservative excisions in most patients (simple excision, 83%; wide local excision, 13%; amputation, 2%), prognosis was excellent. Fifty-eight percent experienced recurrences, but no patient developed metastasis and no patient died of the direct effects of the tumor, although one patient with Maffucci's syndrome developed a concurrent angiosarcoma. We conclude that SCH is a primary benign vascular neoplasm or malformation similar to angiomatosis in which alterations in blood flow might explain some of the secondary features. Areas of diminished blood flow result in vascular collapse with formation of the "cellular" zones, and areas of vascular engorgement with stasis promote thrombosis and organization. Local "recurrences" probably represent contiguous spread along or multifocal involvement of a vessel. Because there is no evidence that this lesion has metastatic potential, we suggest that the lesion be designated spindle cell hemangioma for solitary lesions and spindle cell hemangiomatosis for multifocal lesions.

Bilateral destructive synovitis associated with alpha mannosidase deficiency.

A 13-year-old female with biochemically proven alpha mannosidase deficiency (mannosidosis) developed a bilateral destructive synovitis of the ankle region, a hitherto unreported complication of this disease. Clinically, it was believed to be a pigmented villonodular synovitis. Histologically, the synovium was thrown into villous folds and was infiltrated with clear histiocytes having rare collections of PAS-positive, diastase-resistant material. Electron microscopy demonstrated numerous membrane bound vacuoles filled with granular, amorphous material. This lesion can be distinguished from pigmented villonodular synovitis by its bilaterally symmetrical distribution, the monomorphic population of cells, and the presence of material having the histochemical and ultrastructural properties of (neutral) oligosaccharides.

Elastofibromatous change of the rectum. A lesion mimicking amyloidosis.

We report the case of a 58-year-old woman who had a 7-year history of multiple myeloma and multiple rib fractures and who presented with dysphagia. She underwent thorough gastrointestinal evaluation to rule out the possibility of amyloidosis. Although upper gastrointestinal biopsies were negative, the rectal biopsy was characterized by extensive smudgy eosinophilic deposits in the submucosa that closely resembled amyloid, except that they were not congophilic. Fibers with serrated borders characteristic of those in elastofibroma were identified and confirmed by means of elastic stain and electron microscopy. Elastofibromatous change of the gastrointestinal tract is a rare lesion that has been reported once previously in association with gastric ulcer. This case illustrates that it may occur as a spontaneous or subclinical finding in the absence of other pathologic lesions. The close resemblance between elastofibromatous change and amyloid deposits necessitates the appropriate histochemical and ultrastructural studies.

Pleomorphic hyalinizing angiectatic tumor of soft parts. A low-grade neoplasm resembling neurilemoma.

Fourteen examples of an unusual mesenchymal tumor characterized by sheets and fascicles of mitotically inactive, hemosiderin-stippled, spindled, and pleomorphic cells, situated around an angiectatic vasculature, are described. The 14 tumours developed in eight women and six men (aged 32-83 years) and ranged in size from 2.3 to 8 cm. Eleven cases presented in the subcutaneous tissues, of which eight were located in the lower extremity. All featured prominent clusters of thin-walled ectatic vessels surrounded by perivascular hyaline material representing a combination of fibrin and collagen. In three cases the perivascular hyalinization was so extensive that it constituted more than half of the total tumor area. The tumor cells were similar to those of malignant fibrous hystiocytoma but differed from them by the presence of prominent intranuclear cytoplasmic inclusions, the extreme scarcity of mitotic figures, and the occasional presence of CD-34 expression. These tumors also shared several features with neurilemomas, such as their unusual vasculature, intranuclear cytoplasmic inclusions, lack of mitotic figures, and abundance of mast cells. They could be distinguished from neurilemomas, however, by the usual presence of infiltrative margins and the absence of S-100 protein. Follow-up information on eight patients (6 months to 25 years) indicated recurrences in four cases, with one of the three patients experiencing numerous recurrences over a 25-year period. No patient has developed metastases, however. We suggest that this tumor is a low-grade sarcoma of uncertain lineage in which the vascular changes are, in part, reflective of its slow growth.

Lipomatous hemangiopericytoma: a rare variant of hemangiopericytoma that may be confused with liposarcoma.

We describe the clinicopathologic features and biologic behavior of 16 cases of histologically benign hemangiopericytoma containing a variable amount of mature fat as an intrinsic part of the neoplasm. These so-called lipomatous hemangiopericytomas occurred primarily in men (12 men and 4 women) with a mean age of 54 years (range, 33-74 years). All occurred in deep soft tissue and had an average size of 10 cm when first detected. All were characterized by a relatively sharp border and typical histologic features of hemangiopericytomas, including oval to round cells surrounding a sinusoidal and staghorn vasculature often with perivascular hyalinization. Mature fat varied in amount but usually occupied approximately one quarter to three quarters of the area of tumor. Mitotic activity was low, with more than half the cases having no mitotic activity. Five cases showed moderate nuclear atypia. In four cases, the pericytic regions had sclerotic zones. In contrast to liposarcoma, neither lipoblasts nor isolated atypical hyperchromatic cells within mature fat, as are seen in well-differentiated liposarcoma, were present. Immunohistochemistry performed in four cases showed factor XIIIa in tumor cells and an intricate pattern of immunoreactivity around cells for type IV collagen. CD34 and smooth-muscle actins were identified in two of four cases. Follow-up in seven cases showed no recurrences or metastases within the follow-up period of 1 to 7 years. Because these lesions are located in deep soft tissue and contain large amounts of mature fat, they could be mistaken for well-differentiated liposarcomas in limited biopsy material, although the distinction is easily made in examining the entire specimen. The lipomatous hemangiopericytoma represents yet another example of a bimodal mesenchymal tumor containing mature fat and raises the question of whether a common cytogenetic abnormality can explain the emergence of two clonal populations in this hybrid tumor.

Malignant lymphoma. A study of 75 cases presenting in soft tissue.

We report 75 cases of malignant lymphoma presenting in soft tissue taken from the files of the Armed Forces Institute of Pathology. All histologic subtypes with the exception of lymphoblastic lymphoma were represented. Our findings indicate that virtually any soft tissue site may be involved; there is no sex predilection; and size is not helpful in predicting survival. Among the 55 patients for which race was known, there were no black patients. Thirty-three patients with extensive evaluations at the time of diagnosis had no evidence of disseminated disease, but eight of these exhibited widespread disease within 3 months of diagnosis, and seven of the eight died of disease (median survival, 4 months). The remaining 25 patients had much better outcomes; 18 of 19 with intermediate and high-grade lymphomas were alive and well at a median of 74 months after diagnosis. Some tumors exhibited a propensity for involvement of remote soft tissue sites.

Palisaded myofibroblastoma. A benign mesenchymal tumor of lymph node.

We report 22 examples of an unusual and distinctive benign mesenchymal tumor arising exclusively from lymph nodes of the groin. The tumor, which presents clinically as a swelling, is composed of spindled cells arranged in solid sheets or short, vaguely palisaded fascicles similar to a neurilemoma. The spindled cells blend gradually with large mats of eosinophilic material that appear as thick bands, ellipses, or circular profiles, depending on the plane of section. These eosinophilic structures, which represent a highly characteristic feature of the tumor, contain deeply eosinophilic, collagen-rich cores surrounded by a weakly eosinophilic, actin-rich cuff. The actin within these eosinophilic structures is derived by coalescence of intracellular actin globules extruded from neighboring cells. In all cases, a thin, compressed rim of normal lymph node was identified. Immunohistochemical analysis indicates that the cells express actin but lack S-100 protein, synaptophysin, desmin, keratin, and epithelial membrane antigen. Delicate, linear striations were identified in only two cases by conventional histochemical techniques. The foregoing features suggest that the tumor is related to a myofibroblast or a specialized smooth-muscle cell. These tumors, therefore, probably arise from smooth-muscle-like cells, which are normally present in some lymph node capsules or stroma. Follow-up information on 17 patients indicated that all are alive and well without any evidence of recurrence or metastasis.

Ossifying fibromyxoid tumor of soft parts. A clinicopathological analysis of 59 cases.

We describe 59 cases of a microscopically unique neoplasm that has not been previously reported. The tumor almost exclusively affected adults (range 14-79 years) and had a male predominance (38 men and 21 women). It presented in most cases as a small, painless, well-circumscribed mass (median, 4 cm) in subcutis or muscle. It occurred chiefly in the upper and lower extremities (40 cases) and less frequently in the trunk (11 cases) and the head and neck region (eight cases). Microscopically, the tumor was partly lobulated and composed of small, round cells that had vesicular nuclei and indistinct cytoplasm. Typically, the cells were arranged in a cord- or nestlike pattern within a myxoid matrix that frequently showed transitions toward hyaline fibrosis and focal osteoid formation. In about two-thirds of the cases, the cells contained immunoreactive S-100 protein. An additional typical feature, seen in 48 (81%) of the 59 cases, was the presence of an incomplete shell of mature bone in the capsular region of the tumor. Follow-up information, available in 41 cases, revealed that 11 patients (27%) experienced one or more recurrences. One patient with three recurrences developed a second tumor in the opposite thigh, presumably a metastasis. None of the patients died of the tumor, but three died of causes unrelated to the disease. Although the histogenesis is uncertain, cartilaginous or neural origin seem to be most likely. Until this issue is resolved, we prefer the descriptive and less committal designation of "ossifying fibromyxoid tumor of soft parts."

Hyalinizing spindle cell tumor with giant rosettes: a distinctive tumor closely resembling low-grade fibromyxoid sarcoma.

We report the findings of 19 cases of a previously undescribed spindle cell tumor of soft tissues that resembles a low-grade fibromyxoid sarcoma but contains distinctive rosettelike structures. The tumors occurred principally as a painless, slowly growing, deeply situated mass of the proximal extremities in young to middle-aged adults (age range 14-65 years; mean 38). Although grossly circumscribed, the tumors had infiltrative borders microscopically and were composed of bland spindled cells situated in a hyalinized to myxoid stroma. The most characteristic feature of the tumor was scattered large rosettelike structures that often merged with serpinginous areas of dense hyalinization. The rosettes consisted of a central collagen core surrounded by a rim of rounded cells morphologically and immunophenotypically different from the cells of the spindled stroma. These cells expressed a number of antigens, including S-100 protein, neuron-specific enolase, and leu 22, in contrast to the stroma, which usually lacked these antigens. Of the 12 patients with available follow-up information, one patient treated with simple excision clinically developed local recurrence of the tumor 20 months after initial biopsy. No other recurrences were reported during the limited follow-up period, and no patient developed metastatic disease. However, the favorable prognosis of the patients in our series to date may relate to the limited follow-up period (approximately 3 years), as well as initial treatment by wide excision in nearly half of the patients. We regard the hyalinizing spindle cell tumor with giant rosettes as a distinctive type of low-grade fibroblastic tumor that with time may prove to behave similar to a low-grade fibromyxoid sarcoma and, hence, to represent an unusual variant thereof.

A distinctive cardiovascular lesion resembling histiocytoid (epithelioid) hemangioma. Evidence suggesting mesothelial participation.

This paper presents 14 examples of a distinctive cardiovascular lesion. The patients' ages ranged from 5 to 76 years (mean, 51 years). There were seven male patients and seven female patients. All of the lesions were small and represented incidental surgical findings. Ten were attached to the endocardium, three were free-floating in the pericardial cavity, and one was inside a dissecting aneurysm of the ascending aorta. Microscopically, the lesions were enclosed in a fibrinous network and composed of a solid proliferation of round to polygonal cells with centrally located nuclei. Immunohistochemically, the cells were negative for FVIII-related antigen and lysozyme, but they stained positively for keratin, especially when clustered in small micropapillary or tubule-like formations. The nature and pathogenesis of these lesions are uncertain. Their location and some of their microscopic features originally suggested a relationship with the entity described as histiocytoid (epithelioid) hemangioma. However, their intense immunoreactivity for keratin, occasional presentation in the pericardial sac, and marked morphologic similarities with nodular mesothelial hyperplasia as sometimes seen in hernia sacs point toward the alternative possibility of a reactive mesothelial nature. A possible pathogenetic mechanism for the endocardial cases is ingrowth of pericardial mesothelial cells along a perforation tract that may have developed at the time of a cardiac catheterization. There were no recurrences or metastases in any of the cases.