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Ackerman Atlas(chaptr12)

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Mediastinum

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 Figure 12.1 Location of most common lesions of mediastinum. MPNST, Malignant peripheral nerve sheath tumor

 

Figure 12.2 Fibrosing mediastinitis constricting the superior vena cava resulting in superior vena cava syndrome

 

Figure 12.3 Fibrosing Mediastinitis. Dense ropey collagen bundles surround nerves and vessels

 

Figure 12.4 Gross Appearance of Pericardial Cyst. Note the thin translucent quality of the wall, which is partially covered by adipose tissue

 

Figure 12.5 Microscopic Appearance of Pericardial Cyst. The lining is composed of a single layer of mesothelial cells

 

Figure 12.6 Gross Appearance of Bronchial Mediastinal Cyst. The inner lining has a granular quality

 

Figure 12.7 Microscopic Appearance of Bronchial Mediastinal Cyst. The lining is composed of pseudostratified ciliated respiratory epithelium; the wall contains hyaline cartilage and submucosal glands

 

Figure 12.8 Residual Thymic Tissue. A, This island is predominantly composed of small lymphocytes, but a row of epithelial cells is visible at the periphery. B, This thin elongated strand is predominantly composed of oval to spindle epithelial cells

 

Figure 12.9 A and B, Low-power and higher appearance of nodular hyperplasia of thymic epithelium

 

Figure 12.10 Multilocular Thymic Cyst. The fibrous septa separating the individual cysts are rather thick. The content of the cysts varied from cloudy to blood tinged

 

Figure 12.11 A and B, Microscopic appearance of multilocular thymic cyst. This case was associated with thymic Hodgkin lymphoma, not shown in the photographs. The high-power view shows the stratified squamous lining of the cyst, which is infiltrated by lymphocytes

 

Figure 12.12 Prominent follicular hyperplasia of thymus in a patient with myasthenia gravis. Florid germinal centers are present throughout the organ

 

Figure 12.13 Lobulated large benign thymoma located in anterior portion of mediastinum

 

Figure 12.14 Gross appearance of a thymoma showing distinct multi- nodularity. There is focal cystic change in the larger nodule

 

Figure 12.15 Close-up of the Cut Surface of Thymoma. Note the sharp lobulation induced by the fibrous bands. The pointed ends of some of the nodules are particularly typical of this entity

 

Figure 12.16 Thymoma With Extensive Necrosis and Cystic Degenera- tion. Only one of many microscopic sections showed residual neoplasm. This lesion is likely to be misdiagnosed as a thymic cyst

 

Figure 12.17 Type A (Spindle, Medullary) Thymoma. The pseudo- mesenchymal appearance of the tumor is striking

Figure 12.18 Type A Thymoma With Prominent Rosette Formation. Notice the absence of a central lumen in the rosettes. This tumor should not be confused with thymic carcinoid

 

Figure 12.19 Type B1 thymoma with prominent foci of medullary differentiation

 

Figure 12.20 Type B2 Thymoma. There is an even proportion of neoplastic epithelial cells and non-neoplastic lymphocytes

 

Figure 12.21 Perivascular Space in Type B2 Thymoma. The space is occupied by a proteinaceous fluid and lymphocytes

 

Figure 12.22 Type B3 Thymoma. This tumor, which is predominantly composed of slightly atypical neoplastic thymic epithelial cells, is also known as squamoid thymoma, atypical thymoma, and well-differentiated (organotypic) thymic carcinoma

 

Figure 12.23 Type AB Thymoma. This is one of the most common thymoma subtypes

 

Figure 12.24 Numerous desmosomes and tonofibrils in tumor cells as seen ultrastructurally indicate epithelial origin of a thymoma composed of spindle cells. (Uranyl acetate-lead citrate; x54,500). (From Levine GD, Bensch KG. Epithelial nature of spindle cell thymoma. An ultrastructural study. Cancer. 1972;30:500-511.)

 

 

Figure 12.25 Type B1 (lymphocyte-rich) thymoma stained for keratins (AE1/AE3 and CAM5.2 cocktail). The cytoplasm and cell processes of the neoplastic epithelial cells are strongly immunoreactive for this marker

 

Figure 12.26 Gross Appearance of Thymic Carcinoma. The tumor is invasive and shows foci of necrosis

 

Figure 12.27 Thymic tumor bridging the gap between thymoma and thymic carcinoma. The degree of atypia in the neoplastic cell is such as to justify a diagnosis of thymic carcinoma, but the overall configuration of the tumor and the phenotype of the lymphocytes were those of conventional thymoma

 

Figure 12.28 Chromogranin Reactivity in Some Tumor Cells of Thymic Carcinoma. This is a common finding in thymic carcinoma, as opposed to conventional thymomas

 

Figure 12.29 A and B, Low-power and high-power appearances of thymic squamous cell carcinoma. Note the distinct lobulation in this example

 

Figure 12.30 Low-Power View of Thymic Carcinoma. The tumor lobules are more widely separated by fibrous tissue that more closely resembles a desmoplastic stromal response than the better organized and smaller fibrous septa characteristic of conventional thymoma

 

Figure 12.31 Thymic Carcinoma of Basaloid Type. The tumor islands are connected with the epithelium lining a cystic cavity

 

Figure 12.32 Thymic Carcinoma of Mucoepidermoid Type

 

Figure 12.33 Lymphoepithelioma-like variant of thymic carcinoma

 

Figure 12.34 Thymic Carcinoma of Clear Cell Type. This tumor needs to be distinguished from metastatic carcinoma, particularly from the kidney

 

Figure 12.35 Sarcomatoid Carcinoma of Thymus. Because of the sharp segregation of the carcinomatous and the sarcoma-like components, tumors with this appearance are often called carcinosarcomas

 

Figure 12.36 Thymoma with clusters of myoid cells showing abundant eosinophilic cytoplasm. These cells were strongly immunoreactive for myoglobin

 

Figure 12.37 Micronodular thymoma with lymphoid stroma in which epithelial islands are separated by an epithelium-free lymphoid stroma

 

Figure 12.38 Metaplastic thymoma, previously referred to as low-grade metaplastic carcinoma given bland epithelial component juxtaposed with fibroblast-like spindle cells

 

Figure 12.39 Gross appearance of malignant thymoma invading lung

 

Figure 12.40 A and B, This tumor had the morphologic features of a type A thymoma, yet it was widely invasive

 

Figure 12.41 Ectopic Hamartomatous Thymoma. Thin anastomosing strands of epithelial cells merge with spindle foci having a mesenchyme-like appearance

 

Figure 12.42 A, SETTLE. Spindle epithelial cells of mesenchyme-like appearance surround a well-differentiated gland lined by mucin-producing epithelium. B, Electron micrograph of SETTLE. Portion of a cluster of spindle-shaped epithelial cells that are joined by well-formed desmosomes. Note the tonofilament bundles in the cytoplasm. (x26,000; courtesy of Dr Robert A Erlandson, Memorial Sloan Kettering Cancer Center)

 

Figure 12.43 "Monophasic" SETTLE in which spindle cells predominate resembling monophasic synovial sarcoma. Stromal hyalinization and location within or immediately adjacent to thyroid are useful clues

 

Figure 12.44 Castle. The morphologic appearance is similar to that of thymic carcinoma, of which it probably represents its ectopic counterpart

 

Figure 12.45 Gross Appearance of Thymic Carcinoid. Notice the fleshy appearance and the extensive areas of hemorrhage

 

Figure 12.46 Well-differentiated architectural and cytologic appearance of thymic typical carcinoid. Ribbons and rosettes are evident

 

Figure 12.47 Thymic Atypical Carcinoid. The tumor nests show characteristic central necrosis with calcification

 

Figure 12.48 Thymic carcinoid tumor characterized ultrastructurally by dense-core secretory granules that separate this neoplasm from other thymic tumors. These cells also have prominent rough endoplasmic reticulum, Golgi apparatus, and scattered mitochondria. Inset, Note uniform, membrane-bound, dense-core granules with peripheral halo. (x7450; inset x25,270.)

 

Figure 12.49 Thymic Carcinoid of Spindle Cell Type. This tumor is easily confused with a type A (spindle cell) thymoma

 

Figure 12.50 Small Cell Carcinoma of the Thymus. The tumor cells have finely dispersed chromatin, inconspicuous nucleoli, and scanty cytoplasm. There is associated necrosis

 

Figure 12.51 Thymolipoma. The lesion is composed of an admixture of mature adipose tissue and microscopically normal thymus

 

Figure 12.52 A and B, Well-differentiated liposarcoma/atypical lipomatous tumor arising within the thymus. A fluorescence in situ hybridization (FISH) assay was positive for MDM2 amplification

 

Figure 12.53 Seminoma of Thymus. The tumor is solid and homoge- neous, with focal necrosis. Residual thymic tissue is seen at the periphery

 

Figure 12.54 Seminoma of thymus showing compact nests of large tumor cells surrounded by lymphocyte-rich fibrous septa

 

Figure 12.55 This high magnification view shows the multiple prominent and often irregularly shaped nucleoli that are typical of seminoma

 

Figure 12.56 Seminoma of Thymus. The associated granulomatous response can obscure the true nature of the lesion

 

Figure 12.57 Mature Cystic Teratoma With Prominent Cystic Component. This tumor contained abundant pancreatic tissue, some of which was heavily inflamed

 

Figure 12.58 Yolk sac tumor of mediastinum, with well-developed Schiller-Duval bodies

 

Figure 12.59 Mixed germ cell tumor of the mediastinum comprising a combination of embryonal carcinoma and teratoma (teratocarcinoma) that has undergone massive necrosis

 

Figure 12.60 Somatic adenocarcinoma arising in a mediastinal teratoma from a 25-year-old man with chest and shoulder pain

 

Figure 12.61 Cut surface of nodular sclerosis Hodgkin lymphoma of thymus showing characteristic multinodular involvement of the organ

 

Figure 12.62 Nodular Sclerosis Hodgkin Lymphoma of Thymus. Note the nodular character of the process, the intense intranodular and internodular fibrosis, and the polymorphic nature of the infiltrate

 

Figure 12.63 High-power view of Hodgkin lymphoma of thymus, showing numerous lacunar cells

 

Figure 12.64 Hodgkin lymphoma of thymus accompanied by reactive hyperplasia of the entrapped thymic epithelium, which can simulate a thymic carcinoma of squamous type

 

Figure 12.65 High-power view of lymphoblastic lymphoma of thymus, showing delicate convolutions of the nuclear membrane of the tumor cells

 

Figure 12.66 Diffuse infiltration of mediastinal fat by lymphoblastic lymphoma

 

Figure 12.67 Infiltration and expansion of thymic lobules by lymphoblastic lymphoma

 

Figure 12.68 Gross Appearance of Large Cell Lymphoma With Sclerosis of the Thymus. There is distinct nodularity induced by the fibrous strands. This appearance is not too dissimilar from that of nodular sclerosis Hodgkin lymphoma

 

Figure 12.69 Primary mediastinal (thymic) large B-cell lymphoma with extensive fibrosis and nodularity

 

Figure 12.70 Perivascular cuffing by small non-neoplastic lymphocytes in primary mediastinal (thymic) large B-cell lymphoma. These formations should not be confused with the perivascular spaces of thymoma

 

Figure 12.71 Artifactual cytoplasmic clearing in a case of primary mediastinal (thymic) large B-cell lymphoma which has been formalin fixed

 

Figure 12.72 Malignant Lymphoma of Marginal Zone Type Involving the Thymus. The tumor cells surround and distort Hassall corpuscles. (Courtesy of Dr John Chan, Hong Kong)

 

Figure 12.73 A and B, H&E appearance and CD21 immunoreactivity of dendritic follicular cell tumor of mediastinum. The biphasic pattern resulting from the presence of numerous non-neoplastic lymphocytes can elicit a mistaken diagnosis of thymoma

 

Figure 12.74 Neuroblastoma of mediastinum with prominent rosettes in an adult patient. These tumors can be associated with inadequate secretion of ADH

 

Figure 12.75 Mediastinal Ganglioneuroma. The tumor is solid, yellowish, and homogeneous

 

Figure 12.76 Mediastinal Neurofibroma. The tumor is attached to a large nerve trunk

 

Figure 12.77 Mediastinal Paraganglioma. The well-circumscribed tumor has a characteristic solid, yellow tan cut surface with a vaguely lobular architecture but without the connective tissue septa typical of thymoma. (Courtesy of Dr. J. Carvalho, Minneapolis, MN)

 

Figure 12.78 Hemangioma of Mediastinum. The tumor is formed of large tortuous vessels

 

Figure 12.79 Solitary Fibrous Tumor of Mediastinum. The alternation of hypercellular and hypocellular areas is typical of this entity

 

Figure 12.80 Gross appearance of an atypical lipomatous tumor (well- differentiated liposarcoma) of mediastinum

 

Figure 12.81 Gross appearance of a primary synovial sarcoma of mediastinum

 

Figure 12.82 Mediastinal Metastasis of Prostatic Adenocarcinoma. This tumor was initially misdiagnosed as a thymic carcinoma