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"Chondroid chordoma" is a controversial and confusing entity that was originally described by Heffelfinger and colleagues as a biphasic malignant neoplasm possessing elements of both chordoma and cartilaginous tissue. Because the premise for this distinction was based strictly on histomorphologic criteria, the light microscopic, immunohistochemical, and electron microscopic features of the chondroid and chordoid areas of five chondroid chordomas of the skull base were evaluated separately, and compared to five typical chordomas and six low grade chondrosarcomas. Using light microscopy, chondroid chordoma revealed areas that resembled typical chordoma (chordoid areas) and areas that resembled low grade chondrosarcoma (chondroid areas). However, both the chordoid and chondroid areas had an epithelial phenotype and stained strongly for cytokeratin and EMA as well as S-100. 5'-nucleotidase, an enzyme that has been described in chordoma but not in chondrosarcoma, was found in both the chordoid and chondroid areas of one chondroid chordoma. Electron microscopic studies of both the chordoid and chondroid areas in four of the tumors demonstrated both tonofibrils and desmosomes. Chordoma demonstrated immunohistochemical and electron microscopic features that were nearly identical to chondroid chordoma. Chordoma was cytokeratin, EMA, S-100, and 5'-nucleotidase positive. Ultrastructurally, chordoma exhibited variably-sized vacuoles, abundant rough endoplasmic reticulum (RER), and desmosomes with tonofilaments. In contrast to chondroid chordoma, chondrosarcoma consistently stained for only S-100 protein and was cytokeratin, EMA and 5'-nucleotidase negative. Ultrastructurally, chondrosarcoma demonstrated a flocculogranular matrix, glycogen, abundant RER, and scalloped cellular outlines, but lacked desmosomes with tonofilaments. These findings indicate that "chondroid chordoma" is a variant of chordoma with histologic features that may mimic chondrosarcoma. Despite the resemblance of these hyalinized areas to cartilaginous tissue, these tumors retain their epithelial phenotype. Biphasic differentiation is not present. These findings undermine the original premise for distinguishing "chondroid chordoma" from typical chordoma. The authors propose that these tumors be classified as "hyalinized chordomas," rather than "chondroid chordoma," to clarify their histogenesis and avoid confusion with chondrosarcomas of the base of the skull.
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PMID:Chondroid chordoma. A hyalinized chordoma without cartilaginous differentiation. 757 5

Atypical fibroxanthoma is a superficial variant of pleomorphic malignant fibrous histiocytoma. Histopathologically, it is characterized by a dermal nodule composed of bizarre cells arranged in a haphazard-to-fascicular pattern. These cells are spindle or rounded, pleomorphic and with numerous atypical mitotic figures. Some cells appear polygonal with ample and foamy cytoplasm. We recently encountered two elderly patients with atypical fibroxanthoma on their face. Histopathologically, one of the lesions was composed, almost entirely, of clear cells, whereas in the other one aggregations of clear cells constituted a half of the neoplasm. Atypical multinucleated cells with a Touton-like appearance were present. In addition to clear cells, areas of more conventional atypical spindle cells arranged in fascicles were seen, supporting the diagnosis of atypical fibroxanthoma. PAS staining failed to demonstrate glycogen in neoplastic cells. Immunohistochemistry revealed that neoplastic cells expressed positivity for vimentin, muscle-specific actin, and alpha smooth muscle actin, whereas cytokeratin, S-100 protein, EMA, CEA, and desmin were negative. Ultrastructural studies showed that neoplastic cells contained abundant rough endoplasmic reticulum, mitochondria, and numerous lipid vacuoles within the cytoplasm. Clear-cell atypical fibroxanthoma is a rare variant of atypical fibroxanthoma that should be differentiated from other clear-cell neoplasms of the skin.
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PMID:Clear-cell atypical fibroxanthoma: an uncommon histopathologic variant of atypical fibroxanthoma. 908 54

Myofibroblastic differentiation occurs in 10-20% of all dermatofibromas, affecting < 25% of cells. We report on a series of 36 dermatofibromas collected from > 1,500 fibrohistiocytic lesions (2%), with more prominent (> 25%) myofibroblastic differentiation characterized by markedly slender and elongated spindle cells positive for smooth muscle markers. While most of the lesions did not otherwise differ from ordinary dermatofibromas, three cases (0.2%) from the neck-shoulder region of male adults showed extensive myofibroblastic features (> 90%). Clinically, these three lesions measured approximately 1 cm and had a firm consistency, with the differential diagnosis of some fibrohistiocytic tissue response. Histologically, densely packed cells and prominent, partially nodular, stromal sclerosis with focal palisading of nuclei indicate some overlap with other rare variants of fibrohistiocytic tissue response, such as cellular benign and palisading cutaneous fibrous histiocytoma. Yet, these features together with focal whorled nesting of more epithelioid cells (one case) also caused considerable diagnostic problems to exclude other myofibroblastic as well as (malignant) spindle cell lesions such as (palisaded) myofibroblastoma, dermatofibrosarcoma protuberans, and neurothekeoma. Immunohistochemically, all lesions were markedly (> 90%) labeled for smooth muscle markers (HHF35, anti-SMA) and with NK1C3 (CD57), while a broad panel for other spindle cell tumors, such as pan-keratin, S100 protein, EMA, desmin, CD34, CD31, and KiM1p, were negative. Electron microscopy of two cases revealed prominent endoplasmic reticulum and Golgi complex, numerous intermediate filaments, attachment plaques, and focal basal lamina formation. No recurrence was seen during a follow-up of 9 (two cases) and two years, respectively.
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PMID:Prominent myofibroblastic differentiation. A pitfall in the diagnosis of dermatofibroma. 912 98

A-50-year-old Hispanic man presented to the dermatology clinic with a 0.6-cm eroded, erythematous, scaly plaque on the left side of his neck. On shave biopsy, the lesion was composed of intra-epidermal and invasive dermal cells characterized by a signet-ring appearance. One area suggestive of typical squamous cell carcinoma prompted the inclusion of that entity in the differential diagnosis. Mucicarmine stains were negative, while the extra-vacuolar cytoplasm focally reacted with periodic acid-Schiff staining, the positive reaction for which was abolished by diastase, consistent with glycogen. Malignant cells expressed keratins by reacting to antibodies, Mak6, AE1/AE3, Ker 903, and CAM5.2. Additionally, weak reactivity occurred with antibodies to CEA and EMA. Tumor cells did not express S-100, HM-B45, Leu M1, or actin. By ultrastructural examination, the large vacuoles corresponded to markedly dilated endoplasmic reticulum. A diagnosis of signet-ring squamous cell carcinoma, a rare form of cutaneous squamous cell carcinoma which has been described in only one case report in the last 10 years, was made. Immunohistochemical staining provided information useful in differentiating this lesion from other clear cell and signet-ring cell tumors which involve the skin.
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PMID:Signet-ring squamous cell carcinoma: a case report. 955 Mar 18

Placental site nodules or plaques (PSN-Ps) are nodular benign lesions of the intermediate trophoblast (IT) cells in the endometrium, endocervix, superficial myometrium or fallopian tube, occurring after a remote intrauterine pregnancy. We present a study of 25 cases of PSN-Ps These lesions occurred in patients aged 18 to 44 years. Most were discovered incidentally in endometrial curettage specimens. The specimens were received as part of clinical investigations for menorrhagia, per vaginal bleeding or pelvic pain. None of the PSN-Ps was visible grossly. Microscopically, they were mostly multiple, well-circumscribed, oval or plaque-like cellular nodules. The IT cells typically had abundant vacuolated or eosinophilic cytoplasm. The nuclei were irregular, large, hyperchromatic, often degenerate-looking and either mononucleated, multinucleated or multiclefted. Hyalinization surrounding individual or groups of IT cells, or located in the centre of the nodules, was a constant feature in all cases. The lesional cells were strongly immunoreactive to CAM 5.2, 34 beta E12, AE1/AE3, EMA and vimentin. Some cases showed focal positivity to HCG and HPL. PLAP staining was consistently negative. Ultrastructurally, the IT cells showed prominent nuclear variation in size and shape. The abundant, vacuolated cytoplasm contained some rough endoplasmic reticulum and loosely arranged filaments. This study describes the clinicopathological and immunophenotypic features of 25 cases of PSN-Ps including the ultrastructural findings of one case.
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PMID:Placental site nodules and plaques: a clinicopathological and immunohistochemical study of 25 cases with ultrastructural findings. 1064 2

We have derived a cell line, RE1, from a pre-implantation rat blastocyst, resembling morphologically the L2 cell line from a parietal yolk sac carcinoma of the rat, as well as parietal endoderm cell lines of the mouse. The sub-cellular organization and epithelial characteristics of RE1 cells are described. The cells express cytokeratins of simple epithelia, and vimentin; and demonstrate synthesis of proteins of the extracellular matrix, such as laminin and collagen IV. Extensive Reichert's-like basement membrane is formed by RE1 cells when grown in suspension as aggregates. Cells have a microvillous surface morphology and abundant, rough endoplasmic reticulum which is swollen with apparent secretory material. These morphological and cytochemical features are characteristic of parietal endoderm cells in vivo, and the RE1 cell line is deduced to be rat parietal endoderm. In addition, RE1 cells were examined for expression of stage-specific embryonic antigens: cells reacted with antibody against SSEA-1/TEC-1 and EMA-1, constituting the first observation of parietal endoderm cells expressing the respective epitopes. RE1-cell monolayers did not generate transepithelial resistances or potential differences in vitro, consistent with their formation of leaky epithelia. Our observations on RE1-cell morphology and ultrastructure are consistent with the occurrence of epithelial-mesenchyme transitions in culture.
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PMID:Parietal endoderm cell line from a rat blastocyst. 1116 60

We report the findings from an aspiration biopsy and resection of a chordoma-like tumorous mass in the wall of the thorax of a 36-yr-old man with immunohistochemical, ultrastructural, and cytogenetic studies. The 4-cm oval tumor was an incidental finding on physical examination, and no other lesions were identified after comprehensive radiologic studies. The aspirate was composed of sheets and nests of cells with distinct borders in a myxoid and fibrillary extracellular matrix. The neoplastic cells were uniform and round or polygonal with abundant pale blue vacuolated cytoplasm and small round, central or eccentric nuclei. On electron microscopy, mitochondrial rough endoplasmic reticulum complexes were seen in neoplastic cells. These features were similar to those of a conventional chordoma. However, the cytogenetic pattern, 43, XY ,-1, -2, der (5)t(1p;5q), -6, add(8p) ,add(10q), was not typical. In addition, the neoplastic cells were positive for vimentin, S-100, AE1/AE3, CAM 5.2, and CK 19; were focally positive for EMA and smooth muscle actin; and were negative for cytokeratin 1 and 10 (34 beta E12), CK 7, CK 8 (35H 11B), CK 17, and CK 20. The cytogenetic and immunohistochemical patterns were different from conventional chordoma and its peripheral counterpart, chordoma periphericum, suggesting the diagnosis of parachordoma. To the best of our knowledge, this is the first report of fine-needle aspiration of this newly defined and rare entity.
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PMID:Parachordoma or chordoma periphericum? Case report of a tumor of the thoracic wall. 1282 10

A case of capillary hemangioblastoma located in the peripheral soft tissue of the inner ankle in a 74-year-old woman is presented. The tumor was an unencapsulated but sharply circumscribed nodule 2.5 cm in size, of a yellow-white color. It showed reddish-brown spots with small cysts up to 2 mm filled with blood. Grossly the tumor was not attached to any peripheral nerve. Signs of von Hippel-Lindau's disease were excluded by thorough clinical evaluation. No additional tumor or erythrocytosis was found in the patient clinically. Immunohistochemically, the tumor stromal cell reacted strongly with antibodies to S-100 protein, NSE, and calponin and they were negative with antibodies to GFAP, CD34, CD31, cytokeratins, actin, desmin, EMA, and HMB-45. Endothelium of the capillaries reacted positively with antibodies to CD31, CD34, and Factor VIII-related protein. Capillary pericytes were actin-positive. All cells of the tumor stained positively with antibody to vimentin. MIB1 antibody reacted only in very few cells (<1%). Ultrastructurally, the stromal cells contained electron-lucent cytoplasm with lipid droplets, a small amount of rough endoplasmic reticulum, and glycogen particles. No electron-dense structures typical of secretory granules were seen in the stromal cells. No mutation of coding sequence of VHL gene was found.
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PMID:Primary capillary hemangioblastoma of peripheral soft tissues. 1522 69

Ossifying fibromyxoid tumors (OFMT) are rare soft tissue tumors of uncertain histogenesis and clinical behavior. Since Enzinger, Weiss, and Liang first described 59 examples in 1989 (Am Surg Pathol. 13:817-827), approximately 150 cases have been reported. Their clinicopathologic features are fairly well characterized and their histogenesis remains unknown. Three examples of soft tissue tumors with typical histopathologic characteristics of OFMT were studied: case 1, a 43-year-old female with a 2.5-cm tumor of the back; case 2, a 56-year-old man with an 8-cm thigh mass; and case 3, an 81-year-old female with a 13.5-cm buttock tumor. For immunohistochemistry, formalin-fixed, paraffin-embedded tissue sections were stained with antibodies against cytokeratin, smooth muscle actin, desmin, vimentin, S-100 protein, EMA, and collagen type IV using standard ABC-peroxidase methods. For electron microscopy, tissue samples fixed in EM-grade buffered formalin were processed according to routine methods. Immunohistochemistry showed that the tumor cells were positive for vimentin and S-100 protein in all 3 cases. Stains for collagen type IV revealed diffusely positive staining in the stroma with a tendency for stronger staining around the cell borders in 2 out of 3 cases. Desmin was positive in one and actin was positive in one other case. By electron microscopy, tumor cells were characterized by centrally located round to oval nuclei with varying amounts of cytoplasm containing scanty cytoplasmic organelles. There were rare profiles of rough-surfaced endoplasmic reticulum (RER) and rare mitochondria with areas of condensed intermediate filaments. No tonofilaments or actin filaments were present. There were multiple short web-like processes, some of which were attached to that of neighboring cells by primitive cell junctions. In all 3 cases, lesional cells showed external lamina (EL), which was abundant in case 1, forming redundant scrolls frequently. In case 2, EL was less prominent and incomplete, and interrupted portions of EL were present only along the periphery of cell columns or nests bordering the stroma. In case 3, which behaved as a malignant tumor, the tumor cells were less differentiated spindle cells with primitive cellular features, and EL was rarely found along the short span of tumor cell borders. In this study, tumor cells in OFMT were polygonal to stellate often with multiple short cytoplasmic processes. The tumor cells were found to form cell clusters attached by primitive intercellular junctions between cytoplasmic processes forming intercellular bridges. The cell borders facing the stroma around cell clusters tended to be flat and had incomplete EL, while no EL was present along the cell borders facing the inner aspect of cell clusters. These ultrastructural findings together with immunophenotypic expression of S-100 protein presented closer resemblance to those of modified myoepithelial cells in pleomorphic adenomas of salivary glands and skin appendages rather than peripheral nerve sheath tumors. The authors conclude that these findings render more support to the hypothesis of myoepithelial histogenesis of OFMT. They also conclude that ultrastructural study not only helps accurate diagnosis, but also may aid in predicting malignant behavior by the degree of deviation from the typical examples of OFMT.
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PMID:Ossifying fibromyxoid tumor: modified myoepithelial cell tumor? Report of three cases with immunohistochemical and electron microscopic studies. 1631 54

Superficial acral fibromyxoma (SAFM) is an uncommon tumor of the superficial soft tissues of acral sites. SAFM is a proliferation of fibroblastic cells, within a myxoid to collagenous stroma. The published cases mostly expressed immunoreactivity for CD34, CD99, EMA, and, less frequently, CD10. The authors report an additional case that did not express any of the previously reported markers, including CD34, and antigens of mesenchymal stromal lineage. Ultrastructural study confirmed the tumor cells were typical fibroblasts with cytoplasmic intermediate filaments and numerous cisternae of rough endoplasmic reticulum. The authors describe the first example of SAFM, ultrastructurally studied, with pure fibroblastic immunoprofile.
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PMID:Superficial acral fibromyxoma: immunohistochemical and ultrastructural analysis of a case, with literature review. 1992 77


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