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...".  

Went 2006-03-14 07:24	Dear Mickys: this difficult case I don't dare to solve on the base of the presented clinical data and pictures. I wonder if the patient had autoimmune symptomes? is there a leukocytosis? I wonder if there are epithelial cells outside the capsule as well? Is there a coexpression of the tdT positive cells of CD4 and CD8? CD23 points at residual germinal centers not seen in a normal thymus, in the normal histology I see a heterogenous cell population, not clearly sheet-like on the pictures, there is no indian filing of the tdT positive cells as seen frequently in ALL. In summa, I doubt if this is T-ALL and can not exclude at the moment a thymoma B2 (or less likely B1) as the cytokeratin meshwork is not completely destroyed. Still, the lack of epithelial cells outside the capsule and destruction of the epithalial meshwork would hint at T-ALL.
aorazi 2006-03-15 22:59	I agree that this is a difficult case to solve on   jpgs only. I doubt whether additional immunos. would be of any help. Since the epithelial meshwork seems to be partially preserved, the best indication that this case represents T-ALL/LBL (and not B1/B2 thymoma) would be to show convincing evidence of extrathymic spread of the abnormal lymphoid proliferation (unaccompanied by epithelial cells). I am unable to appreciate this in the submitted figures. Maybe you can show us a jpg with TdT positive cells in extrathymic areas. If you are still undecided you may want to consider getting a BM aspirate/biopsy.
ugnius 2006-03-16 07:33	Dear collegues, I hope that the pictures "TdT lipocytes" and "Ki67 lipocytes" represent EXTRA thymic spread. And diffuselly disorganized architecture of thymus seems to me compatible with any known benign lession, don't you?     I have found the retrospective data about this patient. Maybe, it will help us.
aorazi 2006-03-17 14:20	Thank you for the additional pics which clarify the case. As I said, in cases such as this one with clear cut evidence of extrathymic spread (pleural infiltration with TdT positive blasts is quite characteristic in LBL/ALL cases) the diagnosis of T-cell LBL/ALL is pretty much established. Congratulations for the excellent histo/immunohistology. Coming to you original question, I have never seen cases of mediastinal/thymic LBL/ALL with truly intact thymic architecture.
ugnius 2006-03-17 15:49	Thank you dr.Atilio. In this case there are obvious binary population of blasts0 medium- more clear and atypical and small round (maybe normal precursors?). One more question about the previous Kikuchi like lession: maybe some clearing appears in this situation? LDH remains in a high level...
Went 2006-03-23 07:12	I also agree with the diagnosis of LBL/ALL as is suggested by the tdt positive blasts in the perithymic fat in the additional pictures.
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