Pulmonary Inflammatory Myofibroblastic Tumor Expressing a Novel Fusion, PPFIBP1–ALK: Reappraisal of Anti-ALK Immunohistochemistry as a Tool for Novel ALK Fusion Identification

Abstract

Purpose: The anaplastic lymphoma kinase (ALK) inhibitor crizotinib has been used in patients with lung cancer or inflammatory myofibroblastic tumor (IMT), both types harboring ALK fusions. However, detection of some ALK fusions is problematic with conventional anti-ALK immunohistochemistry because of their low expression. By using sensitive immunohistochemistry, therefore, we reassessed "ALK-negative" IMT cases defined with conventional immunohistochemistry (approximately 50% of all examined cases).Experimental Design: Two cases of ALK-negative IMT defined with conventional anti-ALK immunohistochemistry were further analyzed with sensitive immunohistochemistry [the intercalated antibodyenhanced polymer (iAEP) method].Results: The two "ALK-negative" IMTs were found positive for anti-ALK immunohistochemistry with the iAEP method. 5 0 -rapid amplification of cDNA ends identified a novel partner of ALK fusion, proteintyrosine phosphatase, receptor-type, F polypeptide-interacting protein-binding protein 1 (PPFIBP1) in one case. The presence of PPFIBP1-ALK fusion was confirmed with reverse transcriptase PCR, genomic PCR, and FISH. We confirmed the transforming activities of PPFIBP1-ALK with a focus formation assay and an in vivo tumorigenicity assay by using 3T3 fibroblasts infected with a recombinant retrovirus encoding PPFIBP1-ALK. Surprisingly, the fusion was also detected by FISH in the other case. Conclusions: Sensitive immunohistochemical methods such as iAEP will broaden the potential value of immunohistochemistry. The current ALK positivity rate in IMT should be reassessed with a more highly sensitive method such as iAEP to accurately identify those patients who might benefit from ALK-inhibitor therapies. Novel ALK fusions are being identified in various tumors in addition to IMT, and thus a reassessment of other "ALK-negative" cancers may be required in the forthcoming era of ALK-inhibitor therapy.

Anaplastic lymphoma kinase status in rhabdomyosarcomas

“…Recent reports have suggested that ALK1/ avidin-biotin method may result in suboptimal concordance between immunoreactivity and genomic status. [29][30][31] The differential ALK staining in rhabdomyosarcoma may carry diagnostic value. Subtyping rhabdomyosarcoma can be challenging, particularly when alveolar tumor shows a solid pattern and embryonal tumor shows dense cellularity without an apparent myxoid matrix.…”

Pulmonary Inflammatory Myofibroblastic Tumor Harboring EML4-ALK Fusion Gene

“…Approximately 50% of IMTs harbor an ALK fusion gene, which is normally found in anaplastic large-cell lymphoma, non-small-cell lung cancer (NSCLC) and large B-cell lymphoma, as well as IMT (6). Pulmonary IMTs harboring TPM3-ALK or PPFIBP1-ALK have been reported previously (4,5). EML4-ALK is known to be an abnormality of NSCLC (7), with a prevalence of 1 -5% (8 -10).…”

“…However, anaplastic lymphoma kinase (ALK) fusion gene abnormalities in IMTs are a specific finding that differentiates these tumors from other tumors. Pulmonary IMTs harboring tropomyosin3-anaplastic lymphoma kinase (TPM3-ALK) or protein tyrosine phosphatase receptor-type F polypeptide-interacting proteinbinding protein 1-anaplastic lymphoma kinase (PPFIBPI-ALK) have been reported previously (4,5), while echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) fusion has been considered largely specific to lung adenocarcinoma and an IMT harboring EML4-ALK fusion gene has not been reported.…”

Pulmonary inflammatory myofibroblastic tumor with TPM4-ALK translocation

“…TPM4 as the ALK fusion partner has not been described previously in pulmonary tumor. Six TPM4-ALK fusion cases have been reported in abdomen, mesentery, prostate, urinary bladder and hematologic malignant disease (10,11). These reported TPM4-ALK patients were relatively young at 1 to 25 years of age.…”