25 yrs old female story:  
Episode 1 2008 August: CLINICALLY sarcoma in pelvis minor. Bone pain and walking disability. PATHOLOGY August 2008: casus pro diagnosis (external blocks): "High grade sarcoma, most probably malignant peripheral nerve sheat tumor (MPNST). IH 1: VIMENTIN+, Ki67+ 60%, CD117+ (weak cytoplasmic 20%), S100+ (weak nuclear and cytoplasmic 40%. NEGATIVE: Asmactin/Desmin/PanCK/CD10/CD34/CD3/CD20/EMA/HMB45/Inhib. CHEMOTHERAPY was administered with good reponse (necrosis, below).  
Episode 2 2008 September: CLINICALLY tumor in the inguinal area. Sacral 10 x 15 cm tumor with central degeneration was removed. BIOPSY 2008 September: Malignant tumor totally necrotic, histogenesis obscure. IH 2 (Antigeneity lost): Vimentin/LCA/CD99 (-).  
Eisode 3 2009 May: CLINICALLY: Pelvic MPNST pT2bNxM1, IV st. Mts in the soft tissue, retroperitoneum, lungs, paraaortic nodes. PATHOLOGY 2009 May: High grade clear cell sarcoma: necrosis 80%. IH 3: Vimentin/S-100: 100%+; Ki-67: ~30%; PanCK+ 10% (focal weak); CD99+ 100% (weak like background staining). NEGATIVE: Cam5.2/AsmActin/Desmin/CD34/EMA/HMB-45/Melan A/CD56/CD57.  
MOLECS: LT Ewing and Synovioma specific translocations were not found.  
PHOTOS: From the last episode 3: from Apperio virtual slides taken. Some additional photos (more in square format) by Olympus DP10.  
 
PROPOSAL: Malignant mesenchymal tumour: clear cell sarcoma? malignant ossifying fibromyxoid tumor? Oth.?  
 
ThankyouforyourtouchtoLTpathology

tzankov 2010-05-31 07:19	Classificatory difficult case, some areas look very PEComatous, some like an extrasceletal chondrosarcoma and some are reminiscent of a clear cell sarcoma... why do you think of an ossifying fibromyxoid tumor? where is the shell of bone? did the radiologists detect a shell-shaped ossification? can you add a Masson-Fontana stain and a reticulin stain?
ugnius 2010-05-31 10:38	Working was MPNST (but S100 too strong for MPNST), final hypotesis was clear cell sarcoma (but histologically does not fit very well). The architecture sligthly reminescent of lobulated, monotonous tumor with S100+... And sometimes OFMT shows nonossifying variants after WHO. I'm not sure in this case... The tumor respond very well to sarcoma-chemo and represent "well responding MPNST", what is a little unusual...   I have not Fontana. GSPS pending.
ugnius 2010-05-31 10:40	Despite histological "MPNST like" picture all hypotheses are based on stromg S100+...
tzankov 2010-06-01 17:47	Dear Ugnius, I contacted our soft tissue consultant Prof. Jundt, he does also not see evidence for a particular diagnosis of ossifying fibromyxoid tumor or MPNST, but he is ready to give you, if you wish, a second opinion if you send him the slides and blocks of the case.
ugnius 2010-06-01 17:51	Thank you a lot, dear Alex.
tzankov 2010-06-25 07:26	Dear Ugnius,     together with Prof. Jundt, we analyzed the tumor. The differentials were MPNST vs. extraskeletal chondrosarcoma vs. round cell liposarcoma. The tumor expresses s-100 and nestin, but neither cytokeratin, CD99, actin and SMA, CD34, melanoma markers nor EMA. The tumor cells are surrounded by a laminin and collagen IV+ basment membrane. The FUS gene is not rearranged. We conclude that this is a malignant peripheral nerve sheath tumor.
ugnius 2010-06-26 07:28	Thank you both. one more question: is S100 positivity not too strong for MPNST?
tzankov 2010-06-28 08:10	There are several feature, which are not very typical, but one should consdier that this is the 2nd relapse (phenotyping on relapses is not reliable) and that all other features and marker expression profiles as well as FISH best fit with the common denominator of MPNST.
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