Mediastinum - Sarcomatoid thymic carcinoma

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Mediastinum

Thymic carcinoma

Sarcomatoid thymic carcinoma

Reviewer: Hanni Gulwani, M.D. (see Reviewers page)
Revised: 3 March 2013, last major update December 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Very rare; usually presents as rapidly growing, anterior mediastinal mass
● Must exclude metastases before making this diagnosis
● May arise from malignant transformation of preexisting spindle cell thymoma (Am J Surg Pathol 1999;23:691)
● Aggressive - recurrence, metastasis and death are common

Terminology
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● Also called spindle cell thymic carcinoma

Case reports
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● 43 year old man with tumor arising in metaplastic thymoma (Histopathology 2008;52:409)
● 63 year old woman with tumor arising in metaplastic thymoma (Int J Surg Pathol 2011;19:677)

Gross description
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● Large (mean 15 cm), well circumscribed, locally infiltrative
● Firm cut surface, focal hemorrhage, necrosis, cystic changes

Micro description
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● Irregular fascicles of fusiform and pleomorphic cells with amphophilic or eosinophilic cytoplasm, hyperchromatic nuclei, prominent nucleoli (at least focally), brisk mitotic activity, often atypical mitotic figures
● May have epithelioid foci
● Usually transitional areas with spindle cell thymoma
● May also have lymphoepithelioma-like or anaplastic areas
● Rarely rhabdomyogenic foci with cross striations

Micro images
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Atypical population of spindle cells with frequent mitotic figures

Positive stains
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● EMA (may be focal), keratin (including CAM5.2), vimentin, muscle markers in areas of myogenic differentiation

Negative stains
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● CEA, S100, HMB45, CD5, CD34, CD99

Electron microscopy description
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● Focal junctional complexes between spindle cells, tonofibrils

Differential diagnosis
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● Germ cell tumor
● Malignant schwannoma: triton tumor

End of Mediastinum > Thymic carcinoma > Sarcomatoid thymic carcinoma

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