Mediastinal tumor types

An especially troublesome differential diagnosis is the separation of primary mediastinal synovial sarcoma and PTC. This is because their clinical, electron microscopic, and immunophenotypic features are quite similar. The demonstration of t(X 18) chromosomal translocations in synovial sarcoma—by fluorescence in situ hybridization or traditional cytogenetic analyses—has now made this tumor consistently identifiable. Mesothelioma also enters consideration in this context notably, this tumor type shares possible reactivity for keratin and calretinin with sarcomatoid PTC and synovial sarcoma. However, only mesothelioma commonly expresses the WT-1 protein among these possibilities, and, unlike sarcomatoid PTC or synovial sarcoma, mesothelial tumors do not label for CD99. ... 

Recanalization of tight occlusions of the left innominate vein, which has a long mediastinal course, as may be caused by mediastinal tumor or fibrosis, can require a combined femoral and axillary or a bilateral axillary approach (Fig. 5.6). When the guidewire has crossed the occlusion, it is grasped with a snare, a basket, or a flexible forceps on the other side, and retrieved through the haemostatic valve sheath at the second percutaneous entry point. This makes it possible to insert a PTA catheter or any other stent delivery catheter over a stiff Amplatz-type guidewire, which is controlled and straightened at both ends. 

FIGURE 11.24 Labeling of sustentacular cells for S-100 protein (A) and chromogranin A (B) in mediastinal paraganglioma (C). S-1 00 protein tends to be lost when tumors of this type acquire overtly malignant biological properties. 

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