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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four new cases of ectopic hamartomatous thymoma are presented. The tumor occurred either superficially or deep in the area of the sternoclavicular joint and consisted of solid islands of squamous epithelium which blended with spindled cells. Cysts lined by squamous epithelium, small glands, and fat also occurred in variable amounts. Both the spindled and epithelial regions of the tumor expressed keratin and muscle actin, but neither desmin nor S100 protein. The tumor probably originates from thymic anlage associated with the third pharyngeal pouch (thymus III), although origin from other structures such as thymus IV and the cervical sinus of His are discussed. Our experience indicates that the large size and extreme cellularity of the spindled portion of some tumors may result in the mistaken diagnosis of sarcoma.
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PMID:Ectopic hamartomatous thymoma: clinicopathologic, immunohistochemical, and histogenetic considerations in four new cases. 169 94

Cystic degeneration in thymoma is a relatively frequent but focal event. In rare cases, the process proceeds to the extent that most or all of the lesion becomes cystic. The authors studied ten cases of thymoma undergoing cystic degeneration of such degree that the lesions initially were mistaken grossly and microscopically for nonneoplastic thymic cysts. The patients' ages ranged from 23 to 81 years, and the sex distribution was equal. The lesions were characterized by the formation of multiple large cystic cavities filled with clear, hemorrhagic or grumose material. Histologically, residual solid islands showing the characteristic features of thymoma, i.e., biphasic cell population (epithelial cells/lymphocytes), perivascular spaces, and areas of medullary differentiation, were present within the cyst walls. In contrast with nonneoplastic thymic cysts, the walls of the cavities generally were devoid of an epithelial lining; most of the cysts appeared to predominantly result from extreme dilatation and confluence of perivascular spaces. In some instances, the cystic degeneration of the tumor was accompanied by cystic changes of an inflammatory nature in the surrounding, nonneoplastic thymic tissue leading to firm adhesions and apparent infiltration of adjacent mediastinal structures. None of the lesions in the studied patients recurred during follow-up periods of from 2 to 10 years (average follow-up, 5 years). Cystic thymomas should be distinguished from nonneoplastic congenital and acquired thymic cysts and other primary thymic neoplasms undergoing extensive cystic degeneration. It is important not to misinterpret the apparent infiltration of surrounding mediastinal structures that results from the inflammatory changes that often accompany these tumors as evidence of aggressive or malignant behavior.
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PMID:Cystic thymomas. A clinicopathologic study of ten cases. 172 79

Thymoma is the most common primary neoplasm of the thymus. The majority of thymomas are encapsulated masses and exhibit a benign behavior. Less frequently, thymomas may be locally invasive, or rarely they may metastasize to distant sites. The usual clinical presentation is that of an anterior mediastinal mass found incidentally in an asymptomatic patient. The variable gross features of thymoma and the potential for local invasion result in a variety of radiologic appearances. The most common radiologic manifestation is a rounded, soft-tissue mass of the anterior superior mediastinum. Computed tomography and magnetic resonance imaging typically show a prevascular mediastinal mass of variable size and may be helpful in the evaluation of adjacent structures in cases of invasive thymoma. The treatment of choice is complete surgical excision. Radiation therapy and chemotherapy may be used adjunctively to surgery in the treatment of invasive tumors. The prognosis of encapsulated thymoma is generally favorable. Invasive tumors are associated with a worse prognosis but may respond to radical resection.
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PMID:Thymoma: radiologic-pathologic correlation. 173 61

Thymoma is the most common tumor of the anterior-superior mediastinum, especially in middle-aged or older adults. Microscopically, thymomas can be differentiated from other tumors with which they can be confused by the finding of a mixed population of cells, including neoplastic thymic epithelial cells with numerous processes surrounding activated-appearing lymphocytes. Thymomas can be classified as benign or malignant, and the majority of those that are malignant appear cytologically benign and are locally invasive. Cytologically benign thymomas have been classified as being lymphocyte rich, epithelial cell rich, or spindle cell type. This classification has not been found to be prognostically useful. A new method classifies these tumors as being cortical, medullary, or mixed. This new classification appears to have prognostic significance. Malignant thymomas that are cytologically malignant are uncommon. Such tumors usually are squamous cell carcinomas. Other types include sarcomatoid carcinoma, clear cell carcinoma, basaloid carcinoma, and mucoepidermoid carcinoma. Because other tumors can occur in the anterior mediastinum, electron microscopy and/or immunocytochemistry is helpful in making the distinction. The differential features by ultrastructural and immunocytochemical analysis are reviewed.
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PMID:The diagnosis of thymoma: a review. 175 3

A 62-year-old woman presented with an asymptomatic anterior mediastinal mass. Clinically considered to be a thymoma, the tumor was solid, firm, and composed of hypocellular dense collagen and cytologically bland, spindled fibroblastlike cells growing in a patternless pattern. There was no apparent connection to pleura or pericardium, yet the clinicopathologic features clearly fit with solitary fibrous tumor (SFT) of mediastinum. SFTs occur most commonly in pleura but have been reported in other locations, including the mediastinum, where aggressive behavior has been more common when these tumors are compared to those occurring in pleura. Although it is difficult to predict behavior for all cases of SFT occurring in the mediastinum by cytologic features alone, morphologic criteria for benign and malignant forms have been described. Roughly half the malignant forms will progress, yet the single most important indicator of clinical outcome is whether the tumor can be initially totally excised.
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PMID:Solitary fibrous tumor of the mediastinum. 175 6

Control (C) or Thymoma (T) implanted male C57BL/6J mice received a basal diet containing 16.5% glucose (G) or fructose (F). Compared to the C-G group, the C-F mice consumed more food and less water, and gained more weight. The blood glucose, insulin and triglyceride levels were higher in the C-F than in the C-G mice. Thymoma implantation into the right flank caused a transient decrease in body weight followed by a steady increase due to tumour growth. Tumours were detected earlier and tumour size was greater in the T-F group than in the T-G mice. Tumour chemical composition was similar in both groups. Blood analysis showed that the T mice had lower glucose and higher insulin and triglyceride levels than the C group. Carcasses from the T groups contained more water and ash and less fat than their C counterparts, but the type of sugar did not affect the body composition of the C or T groups. The results suggest that dietary fructose may enhance the growth of tumour via its hyperinsulinaemic action.
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PMID:Insulin-tumour interrelationships in thymoma bearing mice. Effects of dietary glucose and fructose. 176 66

A case of thymoma is presented that was referred for consultation with the differential diagnosis of thymoma and non-Hodgkin's lymphoma. Immunoperoxidase studies performed on fixed, paraffin-embedded sections demonstrated the presence of numerous epithelial cells, supporting the diagnosis of thymoma. However, the pan-B-cell antibody L26 also demonstrated abundant staining, an unexpected finding that may be a potential source of diagnostic confusion. The L26 antibody stained cells with elongate cell processes that interdigitated between and surrounded thymocytes. We pursued this observation by performing immunoperoxidase studies on three thymoma and seven normal thymus specimens using fixed sections. Each thymoma had occasional cells or small clusters of L26-positive cells scattered throughout the neoplasm. In sections of normal thymus, L26-positive cells were also found, almost exclusively in the medullary regions. These cells tended to congregate around Hassall's corpuscles and had elongate cell processes that often surrounded medullary lymphocytes. Occasional small lymphocytes also appeared to be positive for L26. Our results demonstrate that cell populations that express B-cell antigens are consistently found in the thymic medulla and that these cells may be numerous in occasional thymomas. The presence of many L26-positive cells in a mediastinal mass should not dissuade one from making the diagnosis of thymoma if all other findings are consistent with that interpretation.
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PMID:Thymoma with abundant L26-positive 'asteroid' cells. A case report with an analysis of normal thymus and thymoma specimens. 176 16

To determine the factors influencing the extent and recurrence of thymoma, 31 cases of thymoma who had undergone complete resection were analyzed clinicopathologically with special reference to the nuclear area of epithelial cells. The mean tumor size and incidence of recurrence of stage III thymomas were significantly larger and higher than those of stage I thymomas. The nuclear area of epithelial cells of stage III thymomas (72.9 +/- 29.2 micron 2) was significantly larger than that of stage I thymomas (48.4 +/- 13.2 micron 2) or stage II thymomas (49.4 +/- 11.6 micron 2). The nuclear area of thymomas with recurrence (70.2 +/- 21.5 micron 2) was significantly larger than that of those without recurrence (50.2 +/- 12.8 micron 2). In 16 cases who were followed up for 5 years or more, the nuclear areas were over 50 micron 2 in all thymomas with recurrence, while in 8 of 11 thymomas without recurrence it was under 50 microns 2. These results indicated that the tumor size and nuclear area increased step-wisely in association with the advance of clinical stage and that the incidence of recurrence was related to not only clinical stage but also nuclear area. Thymomas with large nuclear area (over 50 microns 2) are considered to be a high-risk group of recurrence and should be carefully followed up.
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PMID:[A clinicopathological study of thymomas, with special reference to evaluation of malignant grade by morphometric analysis]. 177 Jun 79

A 66-year-old woman visited our hospital for further investigation of a coin-shaped lesion in the right lower lung field. After admission, CT-scan revealed an anterior mediastinal tumor. Thymoma and lung metastasis from thymoma were suspected. At thoracotomy, an invasive thymoma involving the left phrenic nerve, the left upper lobe, and the pericardium was found, and the diagnosis of lung metastasis was made. Postoperative pathological findings showed a predominantly lymphocytic thymoma with round and oval-shaped epithelial cells, and the metastatic lung lesion revealed the same findings. Postoperative radiotherapy (4000 rads) and chemotherapy with a combination of CDDP, VDS, and CPA were administered. The metastasis of thymoma is not rare, but most often it is found after operation. In this case the diagnosis of metastatic thymoma was made pre-operatively from a solitary lung lesion.
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PMID:[A case report of invasive thymoma presenting as a solitary metastatic lesion of the lung]. 177 Jun 94

The expression of oncogenes was studied in 12 types of 178 mouse tumors induced by radiations and chemicals. DNA was analyzed in tumors in which the overexpression of oncogenes was noted. Amplification of the myc oncogene was found in chemically induced sarcomas, but not in sarcomas induced by radiation. Activation of oncogenes by small mutations and the inactivation of tumor suppressor genes has to be taken in account in the radiation induction of mouse tumors. We therefore made further analyses of radiogenic thymomas. Loss of heterozygocity was revealed in directly induced thymomas by the deletions of allele specific minisatellite bands. Analysis of a hypervariable minisatellite locus also revealed that these thymoma cells suffered high recombinogenic activity during tumorigenesis. In addition, transfection of cellular DNA to normal Golden hamster cells identified the activated K-ras oncogene in the directly induced radiogenic thymomas. Indirectly induced radiogenic thymomas were tested similarly. Transformed cells from secondary transfection experiment were positive for the mouse-specific repetitious sequences, but devoid of mouse ras oncogenes. Indirectly induced radiogenic thymomas originate from unirradiated normal thymus cells transplanted in irradiated hosts. The spontaneous activation of oncogenes yet to be identified may therefore be involved in the development of this tumor.
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PMID:Analysis of transforming genes in indirectly induced radiogenic thymomas in mice. 182 60


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