Testicular Nodule Incidentally Found in Elderly Male

This comparative analysis of the characteristic ultrastructural features specific for intramuscular myxoma, myxoid liposarcoma, extraskeletal myxoid chondrosarcoma, myxoid malignant fibrous histiocytoma, myxoid variant of dermatofibrosarcoma protuberans, and myxoid neurilemoma is based on our own studies of 52 cases. In spite of the histologic resemblance frequently observed, these tumors can be easily distinguished on the basis of cytoplasmic and extracellular features by electron microscopy. The value of electron microscopy in the diagnosis of myxoid tumors of soft tissues lies mainly in its potential to provide additional information concerning the cell types involved in the neoplastic process and their line of differentiation.     

Skeletal myxoid chondrosarcoma with microtubular aggregates within rough endoplasmic reticulum

A skeletal myxoid chondrosarcoma of the femur was examined by light and electron microscopy. Light microscopic features were characteristic for myxoid chondrosarcoma or "chordoid sarcoma." Electron microscopy disclosed crystalline arrays of microtubules within dilated rough endoplasmic reticulum, a feature previously described in extraskeletal myxoid chondrosarcomas. Tumors with the histologic characteristics of extraskeletal myxoid chondrosarcoma ("chordoid sarcoma") occurring in bone have been rarely reported. We describe herein such a tumor and document the existence of distinct microtubules within the endoplasmic reticulum.     

Undifferentiated perivascular cells in myxoid mesenchymal tumors: an ultrastructural study

The current WHO classification of soft tissue tumors is based on the lineage of differentiation of the proliferating cells. Since mature mesenchymal cells have a broad phenotypic plasticity it has been considered unnecessary to recur to a hypothetical stem cell to explain the origin of these neoplasms. In spite of this assumption, the target cell of the oncogenic mutations in mesenchymal tumors is still a controversial item. Myxoid mesenchymal tumors constitute a heterogeneous group of neoplasms sharing in an ample mucinous matrix that separates neoplastic cells and facilitates their single submicroscopic study under electron microscopy examination. The authors have studied, by electron microscopy, 74 myxoid mesenchymal tumors, including a large variety of nosologic entities, to assess their madurational gradient. In 43 of 74 cases, a common element has been found: medium-sized cells, with high nucleo-cytoplasmic ratio, lacking lineage specific features, which were arranged around the capillary vessels. In some cases, the authors were able to demonstrate gradual differentiation in these cells, as they moved away from the vessels. These features support the hypothesis that at least some mesenchymal tumors originate from perivascular undifferentiated cells. In addition, the findings might contribute to define both topographic and morphologic characteristics of adult stem mesenchymal cells.     

Myxoid leiomyosarcoma of the liver

This is the first report of a myxoid leiomyosarcoma arising in a cirrhotic liver. The tumor was resected from a 64-year-old man. On gross examination, it was soft and hemorrhagic. The tumor was composed of deceptively benign-looking smooth muscle cells with clear cytoplasm suspended in a myxoid stroma with foci of hemorrhage. Immunohistochemistry and electron microscopy confirmed that this was a smooth muscle cell neoplasm. The abundance of glycogen and ultrastructural signs of smooth muscle differentiation were considered consistent with an immature smooth muscle cell phenotype consistent with the diagnosis of myxoid leiomyosarcoma. Since myxoid leiomyosarcomas are aggressive tumors, it is important to recognize them histologically and also bear in mind that these tumors can occur even in unusual extrauterine locations such as a cirrhotic liver.     

Extraskeletal myxoid chondrosarcoma: a study using a quick-freezing and deep-etching method

A case of extraskeletal myxoid chondrosarcoma (ESMC), which developed in the right thigh of a middle-aged Japanese woman, was studied using immunohistochemistry, conventional electron microscopy, and the quick-freezing and deep-etching (QF-DE) method. In addition to typical light microscopic findings of ESMC, conventional electron microscopy indicated that the tumor cells had features of chondrocytes. Immunohistochemically, the tumor cells showed a positive immunoreaction for S100 protein. A diagnosis of ESMC was made. An interesting observation was the ultrastructural features of collagen fibrils in the myxoid matrix highlighted by the QF-DE method. These collagen fibrils consisted of relatively thin collagen (20–35 nm) with pleated surface structures. The surface striation at 65 nm was obscure. We consider that such a finding of collagen fibrils identified by the QF-DE method is one of the characteristics of the myxoid matrix of ESMC, and this is useful for the differential diagnosis of myxoid soft tissue tumors.     

Ossifying fibromyxoid tumor of soft parts: Clinicopathologic, immunohistochemical and ultrastructural study of four cases

Four cases of uncommon soft tissue tumors were investigated histopathologically. All of them consisted of fibrous and myxoid components, and mature bone showed shell-like characteristics. Histological features revealed these tumors were well circumscribed by a thick collagenous fibrous capsule and composed of uniform-sized fusiform cells with eosinophilic cytoplasm and a round or oval nucleus in the myxoid matrix. An incomplete shell of mature bone with lamellar structure was also observed at the periphery. Immunohistochemical and ultrastructural studies were performed. The major component of the proliferating cells in the tumors had positive staining for vimentin, S-100 protein, neuron-specific enolase and synaptophysin. The myxoid matrix was stained by alcian blue and was digested completely by pretreatment with hyaluronidase. Electron microscopy showed the cytoplasm contained dense-core granules measuring 100-200 nm and abundant filaments of an intermediate size. It is suggested that these uncommon tumors might be diagnosed as the 'ossifying fibromyxoid tumor of soft parts' previously described by Enzinger et al., which were derived from peripheral nerve sheath tumors such as neurofibroma and myxoid neurofibroma.     

Microtubular aggregates within rough endoplasmic reticulum: an unusual ultrastructural feature of extraskeletal myxoid chondrosarcoma

Two extraskeletal myxoid chondrosarcomas were examined by electron microscopy. In addition to the well-described ultrastructural features indicative of chondroblastic origin, both of these chondrosarcomas had unusual parallel microtubules packed within rough endoplasmic reticulum. This paper reviews the differential diagnosis of extraskeletal myxoid chondrosarcoma and discusses ultrastructural examination as a valuable adjunct in the diagnosis of this uncommon soft tissue tumor.     

脊索样脑膜瘤临床病理分析

目的：研究脊索样脑膜瘤的临床与病理特征,以提高其早期诊断率。方法：运用组织病理学及免疫组化标记（Ｓ－Ｐ法）对３例脊索样脑膜瘤进行临床病理学和组化（ＰＡＳ）、免疫组化（ＥＭＡ、Ｖｉｍ、Ｓ－１００、ＣＫ）及电镜观察。结果：组织学瘤细胞胞浆内外均见粘液,在粘液基质背景中有成簇或成行的类液滴样细胞,瘤组织中有典型的脑膜上皮漩涡结构,组化及免疫组化示ＰＡＳ（＋）、ＥＭＡ（＋）、Ｖｉｍ（＋）、Ｓ－１００（＋）     

A reassessment of "chordoid sarcoma". Ultrastructural and immunohistochemical comparison with chordoma and skeletal myxoid chondrosarcoma

The relationship of "chordoid sarcoma" (CS) to chordoma and myxoid chondrosarcoma has been debated for several years. In order to reassess this issue, we studied 5 CS, 5 chordomas, and 3 skeletal myxoid chondrosarcomas ultrastructurally and immunohistochemically. By electron microscopy, CS demonstrated smooth cellular outlines, macular intercellular junctions, and cytoplasmic inclusions of matrix-like material. Chordomas displayed a closely similar fine structural appearance, but in addition contained small, membrane-bound, glycogen-containing inclusions. Skeletal myxoid chondrosarcomas resembled CS, except that the former lesions had spiculated cell membranes and lacked intercellular junctions. Immunohistochemically, all CS cases expressed vimentin and lacked cytokeratin (CK). Leu 7 and S100 protein were seen in four cases each of CS, and three of these tumors demonstrated diffuse or focal reactivity for epithelial membrane antigen (EMA). Similar phenotypic features were seen in chordomas, except that all of them stained diffusely for CK, as well as EMA. Skeletal myxoid chondrosarcomas expressed vimentin, S100, and Leu 7 uniformly, but were devoid of epithelial markers. In aggregate, these data support the classification of "chordoid sarcoma" as a form of chondrosarcoma, but reveal that it may exhibit an "epithelial" antigen in some cases.     

A contemporary review of myxoid adipocytic tumors

Myxoid adipocytic tumors encompass a broad heterogeneous group of benign and malignant adipocytic tumors, which are typically myxoid (e.g. myxoid liposarcoma, lipoblastoma and lipoblastoma-like tumor of the vulva) or may occasionally appear predominantly myxoid (e.g. pleomorphic liposarcoma, atypical lipomatous tumor, dedifferentiated liposarcoma, chondroid lipoma, spindle cell/pleomorphic lipoma, atypical spindle cell lipomatous tumor and atypical pleomorphic lipomatous tumor). There have been significant advances in recent years in classification and understanding the pathogenesis of adipocytic tumors, based on the correlation of histologic, immunohistochemical, and cytogenetic/molecular findings. Despite these advances, the morphologic diagnosis and accurate classification of a myxoid adipocytic tumor can be challenging due to major morphologic overlap between myxoid adipocytic and non-adipocytic tumors. This article will provide a review on the currently known morphological, immunohistochemical and molecular features of myxoid adipocytic tumors and their differential diagnosis.     

Intraosseous “Chordoid” sarcoma,chondroblastic or lipoblastic origin?

Summary An unusual sarcoma with myxoid features that apparently originated within the scapula and has been locally aggressive for 10 years is reported. Clinically and by light microscopy it was considered to be a cartilaginous tumor, possibly chordoid sarcoma. By histochemical techniques and electron microscopy it most closely resembles a tumor of brown fat.     

Case Report: Microtubular Aggregates within the Rough Endoplasmic Reticulum of Embryonal Rhabdomyosarcoma Cells: A Case Report

This study presents a case of embryonal rhabdomyosarcoma (ERMS) of the forearm soft tissue in a 12-year-old female, in which microtubular aggregates in rough endoplasmic reticulum (rER) were noted ultrastructurally. Histologically, tumor cells consisted of typical rhabdomyoblastoid cells with abundant eosinophilic cytoplasm and relatively immature, small tumor cells. Ultrastructurally, two different types of tumor cells were also identified by light microscopy. More than half the tumor cells possessed the characteristic features of rhabdomyoblastic differentiation, such as abundant thick and thin filaments with Z-bands. The other tumor cells were less differentiated cells in which microtubular aggregates (MA) in rER were observed. MA in rER have been described in several nonepithelial tumors, including malignant melanoma, osteosarcoma, extraskeletal myxoid chondrosarcoma, and chordoma. ERMS is another example of mesenchymal tumor in which MA in rER are observed by electron microscopy. Considering the differential diagnosis among mesenchymal tumors, it is important to know that MA can be also observed in ERMS.     

Pleomorphic adenoma, II: Ultrastructural organization of "stromal" regions

Findings from an ultrastructural study of 24 major and minor salivary gland pleomorphic adenomas suggest that the principal cell type in the myxoid and chondromyxoid regions of these tumors is a structurally modified myoepithelial cell. This interpretation is based on findings in the transitional zone between myxoid regions and compact cellular areas that have a ductal-acinar organization, that is, are composed of luminal epithelial and modified myoepithelial cells. Survey-type low-power electron micrographs allowed appreciation of the original orientation of the major proliferating component of these tumors to the perimeter of ductal-acinar units. The low-power electron micrographs also revealed residual features of this organization, the early development and subsequent sequential alteration of matrix compartments as tumor cells became increasingly separated by extracellular products, and a variety of myoepithelial cell modifications, such as squamous and chondroid metaplasia, resulting from neoplastic induction. According to the authors' interpretation, modified myoepithelial cells in myxoid and chondromyxoid regions form a continuum with similar tumor cells in transitional and solid areas, forming what can be visualized as markedly expanded and merging ductal-acinar units that tend to converge with similarly altered adjacent neoplastic ductal-acinar units. Thus, a multiplicity of processes are involved in the formation of the complex and varied histologic patterns that characterize pleomorphic adenomas.     

软骨样脂肪瘤1例报道及文献复习

目的探讨软骨样脂肪瘤的临床、病理学特点和鉴别诊断。方法报道1例右小腿软骨样脂肪瘤的临床资料、光镜、组化、免疫组化及电镜观察结果,结合文献讨论。结果镜下见肿瘤由3种成分以不同比例混合构成:①较成熟脂肪细胞体积小的单泡状和多泡状脂肪母细胞,胞质淡染为主,少数细胞呈嗜酸性,核形多样,无异型性及核分裂象,排列成片状和巢状;②脂肪母细胞间黏液透明性软骨样基质;③多少不等的成熟脂肪细胞。PAS染色见脂肪母细胞的胞质内含许多可被淀粉酶消化的深红染颗粒,提示存在糖原。AB染色见黏液透明性软骨样基质呈阳性反应,并部分耐透明质酸酶消化,提示含有硫酸软骨素。脂肪母细胞和成熟脂肪细胞表达S-100蛋白,其中脂肪母细胞对S-100蛋白的表达与脂肪母细胞分化成熟程度相关。电镜观察可见处于不同发育阶段的脂肪母细胞,脂肪母细胞周围被絮状的软骨样基质围绕。结论软骨样脂肪瘤是一种十分罕见的良性脂肪细胞肿瘤的特殊类型,具有独特的组织学形态,应注意与黏液型脂肪肉瘤和骨外黏液样软骨肉瘤等肿瘤鉴别。     

Localized fibrous tumors of the pleura: correlation of histopathological, immunohistochemical and ultrastructural features.

The histogenesis of localized fibrous tumor of the pleura (LFTP) is controversial. We studied 12 LFTP's by light microscopy; by immunohistochemical staining for cytokeratin (CK), vimentin, muscle-specific actin, desmin, S-100 protein, epithelial membrane antigen (EMA) and factor VIII; by electron microscopy in 6 tumors; and by lung digestion for asbestos bodies in 4 cases. Three histologic patterns occurred in combination: 1) collagenous, 2) cellular and 3) hypocellular/myxoid. Hemangiopericytoma-like foci were prominent in the cellular areas of 9 tumors. Unusual features included diffuse small cells in 3 tumors, microcystic foci in 2, macrocystic areas in 5 and tumor giant cells in 4 tumors. Neoplastic cells in all patterns stained positively for vimentin and actin in 9 and 4 tumors, respectively, and were negative for all other markers. CK and EMA were identified in mesothelial and epithelial invaginations only. Ultrastructurally, neoplastic cells demonstrated intercellular junctions, intermediate or thin filaments, dense bodies and rough endoplasmic reticulum. Basal lamina was focally present in 5 tumors, while tonofilaments, desmosomes and short microvilli were observed in one case. Our results support the conclusion that LFTP is a neoplasm of the multipotential subserosal cell, and usually expresses mesenchymal (fibroblastic/myofibroblastic) differentiation. Coexpression of mesothelial features is rare. Lung asbestos body quantitation in 4 patients suggests that there is no association between LFTP and asbestos exposure.     

Squamous cell carcinoma with prominent myxoid stroma

Three cases of a squamous cell carcinoma with a prominent myxoid stroma are reported. One case in a 70-year-old woman had presented as a lump in the breast, the other two presented as polypoid lesions of the larynx and cervix uteri in a 65-year-old man and 61-year-old woman, respectively. The carcinomatous component was immersed in abundant extracellular mucosubstances. In addition to occasional squamous pearls, it displayed immunocytochemical evidence of high-weight keratin present in the neoplastic cells and, in one case, desmosomal attachment under electron microscopy. The extracellular mucosubstances proved to be similar to those seen in connective tissue. The differential diagnosis with histologically similar lesions has been taken into consideration, and it has been suggested that this newly described entity showing abundant myxoid stroma has to be distinguished from numerous benign and malignant myxoid soft tissue tumors.     

Diagnostic pitfalls associated with fine-needle aspiration biopsy in a patient with the myxoid variant of monophasic fibrous synovial sarcoma

Synovial sarcoma (SS) is one of the most common soft tissue tumors that typically presents in the extremities of young adults, but may occur at any site and affect children during the first decade. Herein we discuss a 12-yr-old male who complained of left foot pain and plantar mass. A fine-needle aspiration biopsy of an 8 cm subcutaneous mass was performed revealing a myxoid spindle cell neoplasm. The cytologic differential diagnosis included a myxoid neurofibroma, neurothekeoma, and a myxoid sarcoma. Subsequent excision of the mass revealed a monophasic fibrous SS with myxoid features. Examination of the tissue by fluorescence in situ hybridization confirmed the presence of characteristic SS SYT gene rearrangement at chromosome 18q11.2. This case underscores that the cytologic distinction of mxyoid spindle cell tumors may be challenging. We report the cytologic features of a myxoid monophasic fibrous SS, and discuss its distinction from other benign and malignant myxoid soft tissue neoplasms.     

Intraspinal neurothekeoma (nerve sheath myxoma). A report of two cases

Neurothekeomas (nerve sheath myxomas) are rare benign cutaneous tumors. The authors describe two spinal intradural cases that show histologic, immunohistochemical, and electron microscopic features identical to their cutaneous counterparts. The authors' findings suggest histogenesis from Schwann's cells or undifferentiated nerve sheath precursor cells. Neurothekeomas in unusual locations should be differentiated from myxoid neurofibromas, perineuriomas, and soft tissue myxomas.     

Fine-needle aspiration of leiomyosarcoma: a correlative cytohistopathological study of 96 tumors in 68 patients

To better define the cytological features of various leiomyosarcoma (LMS) variants, we reviewed the fine-needle aspiration material and the corresponding histologic sections of 96 tumors in 68 patients. Histological variants of LMS were as follows: 80 (83.3%) were of the classical/usual, seven (7.3%) were epithelioid, and nine (9.4%) were myxoid. Review of original cytology reports showed that 23 (24%) tumors were diagnosed as LMS and 69 (71.8%) as other types of malignancies. Two (2.1%) cases were reported as suspicious and two (2.1%) were unsatisfactory. The classical variants of LMS were characterized cytologically by various proportions of spindle-shaped, cohesive, small- or large-sized cells arranged in parallel alignment. Large spindle, round, binucleated, giant cells with intracytoplasmic granulations were frequently seen. Blunt-ended nuclei, intranuclear inclusions and mitotic figures were occasionally seen, as well as stromal fragments. The epithelioid tumors were composed of an admixture of small and large, spindle-shaped and round cells, also arranged in parallel alignment. Tumor cells with granular cytoplasm, blunt-ended nuclei, intranuclear inclusions, mitotic figures, fibrous or myxoid stroma were not observed. The myxoid tumors disclosed large amounts of background myxoid matrix containing large spindle-shaped and giant cells. Entities such as leiomyoma, malignant peripheral nerve sheath tumor, monophasic synovial sarcoma, and malignant fibrous histiocytoma should be considered in the differential diagnosis of LMS of the classical type. Epithelioid leiomyoma may share similar cytological features with epithelioid LMS. The cytological features of the myxoid variant of LMS can be easily confused with other types of benign and malignant mesenchymal tumors depicting degenerative myxoid changes and/or a myxoid matrix component.