13.

During some years the Dr Juan Rosai accumulated in diverse consultations several peculiar tumors and seudoneoplásicas tumorlike organizations, which were appraised incompletely characterized, and that appeared in the neck and the gland thyroid. They showed a variable histomorfología that had structural reminiscencias of the fetal thymus, of the completely developed thymus, the thymus in stages of involución, or known tímicos epithelial tumors (2). From this perspective, it fitted then, the possibility that these were derived from ectópico thymus, or of surpluses of stock-market branchial. However, these injuries had been published under an ample range of designations (7).

Juan Rosai (2) described a phantom of four clinical-pathological organizations that includes, in the benign end, a hamartomatosa injury, to which hamartomatoso ectópico denominated "timoma" (THE). In the intermediate strip, the cervical ectópicos calls "timomas" (COMPLEXION), which usually behave like benign, but sometimes can be like local invaders, and from exceptional way to give metástasis. Finally, in the other malignant end, tumors that were designated like "fusado epithelial tumor with tímica similar differentiation" (SETTLE) * and "carcinoma of tímica similar differentiation" (CASTLE) *. (12)

14.

Stains: keratin (strongest for high molecular weight keratin)

Negative: CD20, CD3, TdT

DD: sarcomatoid or anaplastic carcinomas (more atypia), medullary carcinoma (more prominent septa, positive for calcitonin and chromogranin), synovial sarcoma (weak cytokeratin in spindle cells), malignant teratoma (13)