Malformation of the endoplasmic reticulum system evolving into giant inclusions and Auer bodies in acute promyelocytic leukemia: an ultrastructural study of 6 cases.

The endoplasmic reticulum（ER）is the largest membranous network serving as a region for protein, lipid and steroid synthesis, transport and storage. Detailed information about ER-cisternae, ER-tubules and rough endoplasmic reticulum (rER) is scarce in human blood cells. This study describes a series of giant inclusions and Auer bodies in promyeloblasts in six patients with acute promyelocytic leukemia (APL), by light microscopy, transmission electron microscopy (TEM) and cytochemical stains. TEM revealed that giant inclusions and pro-Auer bodies were associated with rER and surrounded by tubular structures composed of degenerated or redundant membrane in promyeloblasts, which corresponded with elements of the ER system. This paper reveals that in the promyeloblasts of APL, ER is the source of and transforms progressively into giant inclusions and Auer bodies.

Structural characterization and origin of surface vesicles in monocytes: another membranous pathway from cytoplasm to cell surface.

The monocytes in acute monocytic leukemia (AML-M5b) were analyzed by scanning and transmission electron microscopy (SEM and TEM) to understand more fully their structure and origin. By SEM, monocytes exhibited localized expansions of the surface, some of which appeared to bud off as surface vesicles (SVs). Filopodial processes and pseudopodia were also present. TEM demonstrated that the SVs were composed of a double-membrane at the pole away from the cell body, and a single membrane nearer to the cell body. In the peripheral cytoplasm, intracellular vesicles (IVs) had the appearance of vacuoles and were enclosed by single membranes. Most SVs were characterized by a notch as a rER edge and an expanded head. Filopodial processes had the same thickness of 40 nm as the SV walls, which suggested a close developmental relationship between the two. Pseudopodia between SVs were irregular in size. Rod-like rER cisternae were prominent in the peripheral cytoplasm and some showed a close physical juxtaposition as to suggest a transition from rER to IVs to SVs. Ultrastructural cytochemistry demonstrated activity of 5'-nucleotidase over rER, SVs, filopodial processes and pseudopodia, and a patchy reaction over other areas of plasma membrane. Overall, the results indicated that rER transforms into SVs, filopodial processes and pseudopodia, as a way of integrating cytoplasmic membranes into the plasma membrane.

Development of Auer bodies from giant inclusions associated with rough endoplasmic reticulum in acute promyelocytic leukemia.

Giant inclusions and Auer bodies in promyeloblasts were investigated in a study which included transmission electron microscopy (TEM) for morphology and ultrastructural cytochemistry for myeloperoxidase in 10 patients with acute promyelocytic leukemia (APL). Ultrastructural cytochemistry demonstrated positive myeloperoxidase reactivity in giant inclusions, expanded rER cisternae, Auer bodies and primary granules. TEM revealed that giant inclusions were adorned by degenerated rER membrane, some of them sharing features with Auer bodies. We hypothesize a novel origin for Auer body development in promyeloblasts of APL, namely that they originate from peroxidase-positive and expanded rER cisternae, and that primary granules were directly released from these expanded rER elements, bypassing the Golgi apparatus.

Ultrastructural characteristics of erythroid cells in congenital dyserythropoietic anemia type II, with a focus on peripheral cisternae and double membranes.

Peripheral cisternae and double membranes (PCDMs) in erythroid cells are a landmark of type II congenital dyserythropoietic anemia (CDA). To gain further insights into the mechanism of dyserythropoiesis, erythroblasts and erythrocytes in bone marrow were studied in 22 Chinese patients with CDA Ⅱ by transmission electron microscopy. The study demonstrated an increase in all patients in erythroblasts with PCDMs with development from pro-erythroblast to red blood cells. PCDMs often connected with cisternae of endoplasmic reticulum (ER) and the perinuclear space, and were accompanied by karyopyknosis, karyolysis and disruption in polychromatic and orthochromatic erythroblasts. The results suggest that PCDMs are transformed from ER during erythropoiesis and participate in the dissolution and deletion of late erythroid cells in patients with CDA II.

Lipogenic stromal cells as members of the foam-cell population in human atherosclerosis: Immunocytochemical and ultrastructural assessment of 6 cases.

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.

Histopathological and ultrastructural study of carotid atherosclerotic plaques: a study of four cases.

To clarify the characteristics and origin of the cellular components in atherosclerosis, carotid atherosclerotic plaques (CAPs) of four patients were studied by light microscopy using hematoxylin-eosin, Congo red and alpha-smooth-muscle actin stains, and by transmission electron microscopy of different regions of CAPs. By light microscopy, CAPs were composed of 1) a fibrous cap; 2) an atherosclerotic core presenting focal fibrosis, neovascularization, hemorrhage, necrosis, chondrification and ossification; and 3) a basal band composed of a hyperplasic pseudo-media and affected tunica media. Ultrastructurally, the CAPs contained a diversity of cells including fibroblasts, myofibroblasts, osteochondrocytes, vascular smooth-muscle cells, foam cells and other myoid cells characterized by varied features of the above mentioned cells. The results indicated that CAPs were derived from a proliferation of multipotential mesenchymal stem cells, leading to the presence of degenerated foam cells and lipid-laden cells.

Ultrastructural alterations of megakaryocytes in thrombocytopenia: A review of 43 cases.

Thrombocytopenia is a frequent occurrence in a variety of hematopoietic diseases; however, the details of the mechanism leading to low platelet count remain elusive. Megakaryocytes are a series of progenitor cells responsible for the production of platelets. Alterations in megakaryocytes in the bone marrow are a causative factor resulting in thrombocytopenia in varied diseases. Based on ultrastructural analysis of incidentally encountered megakaryocytes in 43 patients with blood diseases marked by low platelet counts, electron micrographs demonstrated that aberrant megakaryocytes predominated in idiopathic thrombocytopenic purpura, aplastic anemia, and myelodysplastic syndrome; autophagy, apoptosis, and cellular damage in megakaryocytes were a prominent feature in aplastic anemia. On the other hand, poorly differentiated megakaryocytes predominated in acute megakaryoblastic leukemia (AMKL) although damaged megakaryocytes were seen in non-AMKL acute leukemia. This paper documents the ultrastructural alterations of megakaryocytes associated with thrombocytopenia and reveals distinctive features for particular blood diseases. A comment is made on future avenues of research emphasizing membrane fusion proteins.

Morphological features of fascia lata in relation to fascia diseases.

Fascia lata is an important element of the fascial system, which forms the continuum of connective tissue throughout the body. This deep fascia envelops the entire thigh and hip area and its main function is to transmit mechanical forces generated by the musculoskeletal system of the lower extremities. Fascia lata is also known as a useful and easily harvested graft material. Despite its crucial role in lower extremity biomechanics and wide-ranging applications in plastic and reconstructive surgery, both the structure of fascia lata and particularly the cells populating this tissue are relatively unexplored and therefore poorly understood. The aim of this study was to characterize the main cell populations encountered within human fascia lata and to try to understand their role in health and diseases. Pathologically unchanged human fascia lata was obtained post mortem from adult males. The specimens were analyzed under light, electron, and confocal microscopy. On the basis of different visualization techniques, we were able to characterize in detail the cells populating human fascia lata. The main cells found were fibroblasts, fibrocytes, mast cells, cells showing myoid differentiation, nerve cells, and most interestingly, telocytes. Our results supplement the formerly inadequate information in the literature regarding the cellular components of deep fascial structure, may contribute to a better understanding of the pathogenesis of fascial disorders and improve fascia lata application as a graft material.

On the maturation of megakaryocytes: a review with original observations on human in vivo cells emphasizing morphology and ultrastructure.

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.

Activation of monocyte-derived cells in the bone marrow of myelodysplastic syndrome.

OBJECT: To study the relationship between monocyte/histiocyte activation and myelodysplastic syndrome (MDS). METHODS: Analyzing ultrastructure and myeloperoxidase reaction of nucleated cells in bone marrow from 59 cases of MDS by transmission electron microscopy. Four groups of MDS were subdivided on the basis of their content of activated inflammatory cells - morbid hematopoiesis with minimal inflammatory cell activation (MH-MICA); MDS with monocytic system activation (MSA); MDS with lymphocyte activation (LCA); and MDS with granulocyte activation (GCA). RESULTS: About 20, 22, 7, and 10 cases were classified as MH-MICA (34%), MSA (37%), LCA (12%), and GCA sub-types (17%), respectively. About 3, 5, 0, and 3 cases from MH-MICA, MSA, LCA, and GCA, respectively, underwent leukemic transformation within 2 years. CONCLUSION: The findings suggest that activation of inflammatory cells in bone marrow is an important feature of MDS, and that monocytes/histocytes are perhaps the most prominent cellular participants in the pathogenesis of MDS.

Morphologic characteristics of blastic plasmacytoid dendritic cell neoplasm: a case report.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare aggressive lymphoma derived from plasmacytoid dendritic cells or precursor dendritic cells. Despite some 240 reported cases, its morphology and especially ultrastructure has not been satisfactorily studied. A case is reported of a 13 year old boy, who, despite chemotherapy, died within a 12-month period. The electron microscopy findings - microvillous processes, nuclei with slight irregularities, a moderate amount of heterochromatin, and rough endoplasmic reticulum in the form of long, narrow profiles, often in parallel arrangements - taken together, serve to distinguish BPDCN from other neoplastic cells, such as monocytes, plasma cells and the cells of chronic lymphocyte leukemia.

Congenital dyserythropoietic anemia in China: a case report from two families and a review.

Congenital dyserythropoietic anemias (CDAs) are a group of hereditary disorders characterized by ineffective erythropoiesis and distinct morphological abnormalities of erythroblasts in the bone marrow. Most cases of CDA, caused by a wide spectrum of mutations, have been reported from Europe and Mediterranean countries, while a few cases have been described in China. Here, we present three cases of CDA, one from one family and two from a second unrelated family, with typical morphologic features and clinical presentations. Sequence analysis of CDA-related genes revealed that the proband with CDA Ι in the first family was a compound heterozygote of CDAN1 with mutation IVS-12+2T>C and c. 3389C>T, while both probands with CDA ΙΙ in the second family were a homozygote of the SEC23B gene with mutation c.938G>A (R313H). This study suggests that more patients with CDA, sharing a phenotype and genetic background like those of European and Mediterranean origin, remain to be diagnosed and reported in China.

Analysis of monocyte and histiocytic cell populations in bone marrow of patients with confirmed and suspected cases of reactive histocytosis.

OBJECTIVE: To describe characteristics of monocytes and histiocytes in the bone marrow of patients with a confirmed and suspected diagnosis of reactive histiocytosis. METHODS: 14 patients with a confident diagnosis of reactive histiocytosis or with a suspected diagnosis were inpatients at the Tianjin Blood Diseases Hospital between 2008 and 2012. Nucleated cells from bone marrow were observed by light microscopy - morphologically and immunohistochemically for histiocyte antigens - and ultrastructurally by transmission electron microscopy. RESULTS: Monocytes, atypical histiocytes, macrophages, hemophagocytes, reticular cells and dendritic cells were significantly increased in 9, 9, 5, 3, 3 and 2, respectively, of the 14 cases. Atypical histiocytes expressed some morphological characteristics of promonocytes. CONCLUSION: Monocytes, atypical histiocytes, macrophages, hemophagocytes, reticular cells and dendritic cells were increased in different relative degrees in patients with bone marrow reactive histiocytosis or suspected reactive histiocytosis. The increase in numbers of monocytes, atypical histiocytes and macrophages was a particularly significant feature. It is argued that atypical histiocytes with immature monocyte features might be precursors of hemophagocytes, reticular cells or dendritic cells.

Ultrastructurally confirmed myofibrosarcoma: a series of 10 new cases, with a discussion on diagnostic criteria.

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.

Intra-abdominal clear-cell sarcoma: a report of 3 cases, including 1 case with unusual morphological features, and review of the literature.

Clear-cell sarcoma (CCS) is a soft-tissue neoplasm that morphologically resembles cutaneous malignant melanoma but has a distinct molecular profile. Gastrointestinal and intra-abdominal CCSs are very rare. Here, the authors present 3 cases of intra-abdominal CCS and review the literature. Of these cases, 2 involved the small bowel, and 1 involved the peritoneum. Cases 1 and 3 had the characteristic CCS morphology, but case 2 was morphologically unusual and therefore difficult to diagnose. It had relatively small cells with less prominence of clear cells; many pseudoglandular structures were also present. It also showed aberrant expression of epithelial membrane antigen (EMA). The other 2 cases also involved some diagnostic uncertainty and were therefore referred to specialized centers. The authors wish to emphasize the importance of molecular studies in making a conclusive diagnosis of intra-abdominal CCS.

Stromal cells in the human gut show ultrastructural features of fibroblasts and smooth muscle cells but not myofibroblasts.

The free spindled cells of the lamina propria of the gut have been reported as showing fibroblastic, smooth-muscle and myofibroblastic differentiation. A precise understanding of the differentiation of these cells is essential for appreciating their functions, and this paper addresses this question using ultrastructural analysis. Histologically normal samples from different areas of the gastrointestinal tract were studied. Both subepithelial stromal cells, lying immediately beneath the basal lamina, and the deeper interstitial stromal cells, were studied. Subepithelial and interstitial cells had comparable features, reinforcing the idea that these formed a single reticulum of cells. Two major cell types were identified. Some were smooth-muscle cells, on the basis of abundant myofilaments with focal densities, glycogen, an irregular cell surface, focal lamina and multiple attachment plaques alternating with plasmalemmal caveolae. Some cells had a lesser expression of these markers, especially of myofilaments, and were regarded as poorly differentiated smooth-muscle cells and descriptively referred to as 'myoid'. Other cells were fibroblastic to judge by prominent rough endoplasmic reticulum, an absence of myofilaments and lamina, but presence of focal adhesions. The fibronexus junctions of true myofibroblasts were not seen. The study emphasises that the smooth-muscle actin immunoreactivity in this anatomical site resides in smooth-muscle cells and not in myofibroblasts, a view consistent with earlier ultrastructural and immunostaining results. The recognition that these cells are showing smooth-muscle or fibroblastic but not true myofibroblastic differentiation should inform our understanding of the function of these cells.

Gastrointestinal stromal tumor with structures resembling intracytoplasmic lumina.

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gut. It is characterized by positive immunostaining for CD117, and bears mutations in the c-kit or PDGFRA genes. Its origin remains uncertain. GISTs mainly possess primitive smooth muscle or neuronal differentiation. Although an epithelioid pattern of GIST is a common finding on light microscopy, true epithelial differentiation has never been demonstrated by either immunohistochemistry or ultrastructural study. Here the authors report an epithelioid GIST of the stomach, immunopositive for CD117, DOG1.1, CD34, and PDGFRA, with slight cytoplasmic staining for epithelial membrane antigen. One heterozygous mutation on codon 842 of exon 18 of the PDGFRA gene was also found. Ultrastructurally, tumor cells had plentiful organelles, including some membrane-bound, dense-core granules and cytoplasmic vacuoles. Intermingled thin cellular processes were also found. Unusually, there were many structures resembling glandular epithelial intracellular lumina with processes. The processes, although resembling microvilli, did not have filament cores, while the lumina were either empty or contained some dense or flocculent content of uncertain nature. True intracellular lumina are very rare in GIST and the authors present findings related to this issue, with a discussion on their nature, origin, and significance.

A primary sclerosing epithelioid fibrosarcoma of the pubic bone, with evidence of divergent epithelial differentiation.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare variant of fibrosarcoma, described initially by Meis-Kindblom et al. in 1995 (Meis-Kindblom JM, Kindblom L-G, Enzinger FM. Sclerosing epithelioid fibrosarcoma: a variant of fibrosarcoma simulating carcinoma. Am J Surg Pathol. 1995;19:979-993): more than 80 cases have been documented clinicopathologically since. Bone is a rare primary site for SEF, with only 2 cases so far reported. This paper documents the detailed clinical, histological, immunohistochemical, and ultrastructural features of a case occurring in the pubic bone of a 57-year-old diabetic woman presenting with a history of pain and compromised mobility involving her hip. Radiology revealed a destructive lesion in the right pubic bone. The lesion was resected, and 7 months postoperatively it recurred. The patient died following metastases to multiple bony sites and liver, some 4 years after the onset of symptoms. Histologically, the tumor was consistent with SEF, although it showed some anomalous immunostaining, which, however, is typical of the tumor (for example, for S-100 protein and epithelial membrane antigen). By electron microscopy, some rough endoplasmic reticulum was present, but also tonofibrils and desmosomes. The overall features were of an SEF with the ultrastructural but incomplete immunohistochemical evidence for divergent epithelial differentiation. The differential diagnosis of this tumor is discussed.

Pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation: a single case report.

Rhabdomyosarcoma has traditionally been subclassified into alveolar, embryonal, and pleomorphic variants. Less commonly, spindle-cell, neuroendocrine, sclerosing, and lipid-rich or clear-cell subtypes are seen. The author recently encountered a myogenic sarcoma, with all the common markers of rhabdomyosarcoma, but expressing the unusual features of alpha-smooth-muscle actin and abundant rough endoplasmic reticulum (rER). This myogenic sarcoma, therefore, exhibited four lines of differentiation, and is documented here. The patient was a 65-year-old man with an inguinal soft tissue mass. Following surgical excision, the patient was given radiotherapy and was well without disease after 6 years. The tumor was positive for vimentin, desmin, alpha-smooth-muscle actin, alpha-sarcomeric actin, myogenin, MyoD1, and CD68. Cytoplasm was dominated by abundant rER intermingled with lipid droplets and lysosomes. Cell surfaces exhibited microvillous processes and focal adhesions, but no lamina. Subplasmalemmal smooth-muscle-type myofilaments with focal densities and rare sarcomeric filaments were seen. The low level of expression of some markers was interpreted as consistent with a poorly differentiated tumor. Given the four lines of differentiation--striated muscle, smooth muscle, fibroblastic, and histiocytic--a name reflecting its phenotype would be pleomorphic rhabdomyosarcoma showing smooth-muscle and fibrohistiocytic differentiation.