The open biopsy was taken from 13 yrs old boy popliteal deep seated 15cm tumor, spreading along large vessels and infiltrating muscles. The inguinal lymph node was biopsed too. CT reveals multiple lymph nodes (visceral and paraaortal) and 15cm tumor in the popliteal area without bone destruction ("lymphoma like picture" on CT).  
HISTORY: 1 month ago the tenderness and pain inth left feet. ESR and CRB were elevated. The transitory fever was noticed. The vasculopathy was suspected. The patient is obese (88kg). Any B symptoms today present.  
HISTO: 1 MUSCLE: There are small infiltrates of high proliferative rate small blue tumor cells in the stratiated muscle. The apoptotic bodies, nuclear ireegularities are prominent. 2. NODE (fragmented): The lymph node is infiltrated from sinus side by pleomorphic cells with irregular nuclei and scant-medium bluish clear cytoplasm. THERE ARE ANY SIGNS of plasmablastic appearance.  
IH: ALK1(+/++) 95%, TdT/CD34(-), EMA/PanCK(-), CD3/CD20/CD30/LCA/CD68/CD79a/MPO(-), CD99(-), CD138(-), Ig kappa (+/+++)> Iglambda (???), Mum1(-), CD4/GranzymB/CD8(-), Bcl6/CD10(-). Ki67 proliferative fraction 90% (++), PAX-5(-/+)(single nuclei +/- ), HMB45/S100(-), Desmin (+/++)(IN PERIPHERY OF THE SECTION MAINLY and dott like cytoplasmic in central part in the single cells) .  
PENDING: AsmActin, MyoD1, Myogenin, Vimentin.  
 
The first idea was ALCL, but CD30 seems to be negative...  
SO...PROPOSED DIAGNOSIS: HIGH GRADE LYMPHOMA, MOST PROBABLY DLBCL WITH ALK1 EXPRESSION.  
FINAL DIAGNOSIS: ALVEOLAR RHABDOMIOSARCOMA.  
 
QUESTION: the strange IH profile, maybe due to technical reasons.  
 
NOTE: The HISTO quality is SUBOPTIMAL.  
Due to inconclussive immunophenotype I have had an idea about effaced immunogennity of tissue or lab quality problems.  
 
Thank you for comments.