1. The extirpation of mediastinal mass was performed to 43 yrs old male.  
HISTO and IH: photos below.  
COMMENT: There is disordered architecture with dispersed PanCK+ network with some nodularity (reminescence of thymus structure), CD23+ single FDC nodules. Mixture of dark (smaller lymphoid cells- precursors) and bright (larger tumor blasts) areas are present with microcystic change. High level of Ki67+ activity. TdT+ Ki67+ cells are present in extracapsular lipocytic areas.  
PROPOSED DIAGNOSIS: Precursor T lymphoblastic lymphoma/leukaemia in thymus gland?  
QUESTION: What criteria may help in case if thymus architecture would be intact???  
2. Additional retrospective materials: 2003 the resection of mediastinal tumor and pleura was performed (identical findings). HISTO and IH identical: the same blastic population in lymphoid tissue(lymph node?), extralymphoid fat and pleural soft tissue. NEW PHOTOS NAMED "2...".