ALK expression in rhabdomyosarcomas: correlation with histologic subtype and fusion status.
Immunohistochemical staining for anaplastic lymphoma kinase (ALK) has been described in rhabdomyosarcomas (RMS), especially the alveolar subtype. Previous studies have yielded conflicting results regarding the pattern of staining (nuclear versus cytoplasmic), and there has been no correlation with PAX3-7/FKHR fusion status. This study was undertaken to evaluate ALK receptor protein expression in a large series of RMS; to correlate these results with fusion status; and to investigate the possibility of 2p23 amplification or translocation using fluorescence in situ hybridization (FISH). Sixty-nine cases of RMS were examined and classified as alveolar RMS (ARMS), embryonal RMS (ERMS), or unclassifiable RMS (URMS) subtypes. Anaplastic lymphoma kinase immunohistochemistry was performed using anti-human CD246 antibody; cases were considered positive when more than 50% of cells had moderate or intense cytoplasmic and/or nuclear staining. There were 30 ARMS, 37 ERMS, and 2 URMS subtypes. Reverse transcription-polymerase chain reaction for PAX3/PAX7-FKHR fusion analysis had been done in all cases of ARMS, in 27 of 37 cases of ERMS, and in both URMS cases. Anaplastic lymphoma kinase staining was positive in 16 of 30 ARMS (53%) and 9 of 39 nonalveolar RMS (23%) cases (P < 0.05). Of the 21 ARMS cases with PAX3-FKHR fusion, 10 of 21 (48%) were positive for ALK staining; of the 6 ARMS cases with PAX7-FKHR fusion, 3 of 6 (50%) were positive for ALK staining; and 3 of 3 (100%) of the fusion-negative ARMS were positive with ALK staining. When comparing each of the ARMS subtypes, statistical significance was not reached. All positive cases showed dot-like cytoplasmic staining; nuclear staining was not seen. Of a subset of 6 ALK-positive ARMS submitted for break-apart FISH for the ALK locus, there was no evidence of a translocation; 1 case had ALK amplification and 2 had low-level gains of the ALK gene. We conclude that there is ALK overexpression in RMS, more commonly in ARMS than in ERMS, most likely independent of fusion status. Amplification or upregulation of ALK may underlie ALK protein overexpression.
Corao
Diana A
DA
Department of Pathology, A. I. DuPont Hospital for Children, Wilmington, DE, USA. dcorao@nemours.org
Biegel
Jaclyn A
JA
Coffin
Cheryl M
CM
Barr
Frederic G
FG
Wainwright
Luanne M
LM
Ernst
Linda M
LM
Choi
John K
JK
Zhang
Paul J
PJ
Pawel
Bruce R
BR
D000293:Adolescent; D000077548:Anaplastic Lymphoma Kinase; D014408:Biomarkers, Tumor / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008297:Male; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D051763:PAX7 Transcription Factor / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis*; D020794:Receptor Protein-Tyrosine Kinases; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018232:Rhabdomyosarcoma, Alveolar / Q000235:genetics* / Q000473:pathology*; D018233:Rhabdomyosarcoma, Embryonal / Q000235:genetics* / Q000473:pathology*
D014408:Biomarkers, Tumor; D015514:Oncogene Proteins, Fusion; C523321:PAX3-FKHR fusion protein, human; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases