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Some view ultrastructure as key to myofibrosarcoma diagnosis, whereas others argue that electron microscopy is too little used in contemporary practice to be considered an important diagnostic tool. These views are discussed in the context of 10 ultrastructurally confirmed cases of myofibrosarcoma, some occurring at rare sites such as skin and penis. Patient age ranged from 21 to 83 years, with a 6:4 male to female ratio. Size ranged from 2 to 7.5 cm and all had infiltrative margins. Histologically, all consisted of variably cellular fascicles of spindle cells with mild to moderately pleomorphic nuclei, small punctate nucleoli, and eosinophilic cytoplasm. All cases showed α-smooth muscle actin positivity and 2 showed very focal weak positivity for desmin. Ultrastructurally, the tumor cells contained rough endoplasmic reticulum, mainly peripheral smooth-muscle myofilaments, and fibronectin fibrils or fibronexus junctions at the cell surface. The most confident diagnosis of myofibrosarcoma is provided by ultrastructural examination. However, given the right histological appearance, use of a panel of antibodies that includes α-smooth muscle actin, desmin, and h-caldesmon, serves as an acceptable practical way of diagnosing myofibrosarcoma. [ABSTRACT FROM PUBLISHER]

Rectal/anorectal malignant melanomas are highly aggressive tumors with a poor prognosis and low 5-year survival rate. They are also very rare. Of the well-known histological variants of malignant melanoma, the small cell subtype is also very uncommon; consequently, small cell anorectal malignant melanoma is an exceedingly rare occurrence. In this article, the authors provide a detailed clinicopathological description of small cell malignant melanoma of the rectum, documenting clinical, histological, immunohistochemical, and ultrastructural features, to add to the sparse references on this tumor in the literature. The patient was a 53-year-old woman with a mass 2 cm from the anus, which was surgically removed. In histological sections, the tumor was a small cell malignant melanoma, with a tumor cell diameter of 7.6±1.0 µm, and a range of 5.5-10.7 µm (N = 100). Tumor cells were positive for S-100 protein and HMB-45 and contained sparse but unambiguous type II melanosomes. This article is one of the few detailed clinicopathological documentations of a small cell malignant melanoma of the rectum (anorectum) and the first to have the diagnosis confirmed ultrastructurally by the identification of melanosomes. The present case adds to the 3 mainly or entirely small cell anorectal malignant melanomas described in the literature. There are also at least 12 other cases with less well-defined numbers of small tumor cells or with small cells admixed with other cell morphologies. Documentation of these unusual morphological variants is important for identifying any distinctive outcome they might exhibit compared with conventional malignant melanoma. [ABSTRACT FROM AUTHOR]

Cytotoxic therapy in young women with cancer may cause loss of ovarian function, and ovarian cryopreservation has been proposed as a means of preserving fertility. The objective of this study is to assess ultrastructural preservation of follicles in frozen–thawed ovarian cortical strips, previously cryopreserved using dimethylsulfoxide and a standard slow-cool/rapid-thaw protocol. Ovarian cortical strips(patients,n  =  7)were thawed and fixed in glutaraldehyde for epoxy resin embedding electron microscopy according to conventional procedures. Oocytes were generally well preserved, on the basis of plasma–membrane integrity, uniformity of chromatin pattern, mitochondrial and rough endoplasmic reticulum(rER)cisternal integrity, and absence of cytoplasmic and intranuclear clear spaces. Frequently, rER cisternae were distended and intramitochondrial matrices lost. Granulosa cells showed somewhat variable preservation. Some were dark-staining; others exhibited washed-out cytoplasm containing damaged or artifactually expanded organelles. The consistently good preservation of oocytes and the good but more variable preservation of granulosa cells provides scientific validation of one component in the overall clinical procedure of attempting to reestablish fertility in young female patients after cytotoxic therapy for cancer. [ABSTRACT FROM AUTHOR]

To identify the nature of foam cells in atherosclerosis, carotid atherosclerotic plaques (CAPs) from six patients were studied. Hematoxylin-and-eosin, Congo Red and Oil Red O staining were used to study histopathologic alterations in CAPs. CD31, α-smooth-muscle actin (α-SMA), CD68, desmin and S100 were stained immunohistochemically. The ultrastructure of foam cells was analyzed by transmission electron microscopy (TEM). CAPs were shown to be composed of a fibrous cap covering a dome-shaped mass with a peripheral, circumferential fringe merging with a basal band which itself met the tunica media, the latter consisting of smooth-muscle cells (SMCs). The interior of the dome-shaped mass exhibited fibrosis, neovascularization, hemorrhage, necrosis and calcification. Lipid droplets identified by histological stains and TEM were found in the rounded epithelioid foam cells regarded as macrophages, as well as in spindled cells interpreted here as lipoleiomyocytes (lipid-containing SMCs), lipofibroblasts and lipomyofibroblasts; and all these cells were located in different regions of the CAPs. All of these lipid-laden cells were strongly positive for CD68 but negative for desmin. Foam cells were weakly positive for α-SMA, CD31 and S100. The results indicate that the light microscopically identifiable population of foam/lipid-laden cells hide a spectrum of diverse differentiation ranging from the expected macrophage phenotype to non-macrophage phenotypes. The origin of these diverse cell phenotypes in terms of multipotential mesenchymal precursors and the origin of the intracellular lipid are discussed. [ABSTRACT FROM AUTHOR]

Megakaryocytes engage in the synthesis of a variety of molecular and macromolecular constituents to build-up characteristic megakaryocyte structure and form proplatelets in a series of cells from megakaryocyte precursors to the fully matured cell. The process is illustrated in this review by light microscope morphology and transmission electron microscopy, which emphasizes new findings in human in vivo megakaryocytes, thereby making a contrast with the abundant literature on megakaryocytes from experimental animal and human in vitro material. Four stages are identified and described, based on the development of characteristic structures including α-granules, dense granules (dense-core granules), the demarcation membrane system (DMS), and proplatelets. The mechanism of DMS development is discussed, in terms of hypotheses suggesting origin from the plasma membrane, and contributions of membrane from the Golgi apparatus and endoplasmic reticulum. The formation of the marginal zone is also discussed, which is suggested to result from a circumscription of the peripheral organelle-free cytoplasmic fringe by peripheral circular cytoskeletal elements such as cytoplasmic actin and microtubules. [ABSTRACT FROM AUTHOR]