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Oncol Lett
2017 Feb 01;132:593-598. doi: 10.3892/ol.2016.5504.
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A malignant inflammatory myofibroblastic tumor of the hypopharynx harboring the 3a/b variants of the EML4-ALK fusion gene.
Muscarella LA
,
Rossi G
,
Trombetta D
,
La Torre A
,
Di Candia L
,
Mengoli MC
,
Sparaneo A
,
Fazio VM
,
Graziano P
.
Abstract
Inflammatory myofibroblastic tumors (IMT) in the head and neck region are rare neoplasms that generally mimic benign/low-grade neoplasms. Overexpression of anaplastic lymphoma kinase (ALK) has been reported in 50% of IMT cases, secondary to ALK activation by structural rearrangements in the ALK gene, which results in a fusion protein with echinoderm microtubule associated protein like 4 (EML4) in ~20% of cases. The present study describes a case of a 74-year-old woman with a malignant IMT in the right posterior hypopharynx harboring a previously unreported chromosomal rearrangement resulting in EML4 and ALK gene fusion. Strong ALK immunoreactivity was observed in neoplastic cells, while fluorescent in situ hybridization combined with fluorescent fragment analysis and direct sequencing identified the first case of the 3a/b variants of the EML4-ALK fusion gene in IMT. The results of the current study highlight the uncommon occurrence of ALK-positive IMT in the head/neck region and demonstrate the importance of integrating different molecular methodologies to identify unequivocal gene fusion characterization.
Figure 1. Computed tomography scans of the (A) head and (B) neck region revealed a poorly-circumscribed mass (maximum diameter, 5 cm), which involved the posterior wall of the right hypopharynx, dislocating the oesophagus and tracheal axis and infiltrating to the soft palate. Hematoxylin and eosin staining of tumor tissue sections revealed that the tumor was composed of (C) spindle-shaped or (D) epithelioid myofibroblasts arranged in fascicular or storiform-like patterns, admixed with scattered lymphocytes, plasma cells and foamy histiocytes (magnification, ×150). Immunohistochemistry demonstrated that the tumor cells expressed (E) smooth muscle actin, (F) desmin and (G) ALK (magnification, ×150). ALK, anaplastic lymphoma kinase.
Figure 2. (A) Molecular cytogenetic analysis of the FFPE tumor sample, in which the disrupted ALK locus was identified by fluorescent in situ hybridization analysis. The white arrows indicate the split of the green and red probe signals (hybridizing to 5′ and 3′ regions of ALK, respectively) in the tumor cells. (B) Fluorescent fragment analysis in the tissue specimen positive for ALK translocation. RNA from the FFPE tissue (upper panel) and NCI-H2228 cell line (lower panel) was amplified by RT-PCR using an unlabeled EML4 exon 6 forward primer and a fluorescein amidite-labeled ALK exon 20 reverse primer. Two peaks were observed (at 112 and 142 bp) indicating the presence of the 3a/b variants of the EML4-ALK fusion. (C) Fluorescent fragment analysis of the (Ca) inflammatory myofibroblastic tumor tissue and (Cb) control NCI-H2228 cell line using the Agilent 2100 BioAnalyzer. Two different fluorescent peaks were observed at 126 and 152 bp, corresponding to the 3a/b variants of the EML4-ALK fusion. (Cc) The peaks were visualized on the gel resulting from the capillary microelectrophoresis. (D) EML4-ALK fusion variant 3a characterization. (Da) Schematic of the EML4-ALK fusion variant 3. (Db) Sequence electropherogram of the RT-PCR product. (Dc) Fusion junction of EML4 exon 6 (blue) and ALK exon 20 (red) sequences. FFPE, formalin-fixed paraffin-embedded; ALK, anaplastic lymphoma kinase; RT-PCR, reverse transcription-polymerase chain reaction.
