Genetic alterations in periprosthetic soft-tissue masses from patients with metal-on-metal hip replacement.

Adverse soft tissue reactions in patients with metal-on-metal (MoM) hip replacement are associated with cobalt (Co) and chromium (Cr) particles released from the implant. Exposing the patients to long periods of increased metal ions concentrations resulting from the wear of these implants poses an increased risk of genotoxicity/mutagenicity. A variable proportion of patients develop periprosthetic soft-tissue masses or pseudotumors at the site of the implant. There is a concern that exposure to increased metal ions could increase the risk of cancer. In order to investigate whether the periprosthetic soft-tissue mass harbours any cancer- related genetic alterations, we studied DNA isolated from periprosthetic tissues of 20 patients with MoM hip replacement, for copy number alterations and mutations in hotspot regions of 50 cancer genes using aCGH and amplicon-based next generation sequencing. Our results showed copy number gains at 12q14.3 and 21q21.1in tumour from patient diagnosed with liposarcoma. Copy number alterations in periprosthetic tissues were seen in three other patients, one had a region of gain at 9q24.1 affecting JAK2 and INSL6, and two patients had region of gain at 6p21.1, affecting RUNX2. Mutation analysis showed V1578del mutation in NOTCH1 in two patients. The copy number alterations and mutations seen in periprosthetic soft-tissue masses are earlier reported in either haematological malignancies or in osteoblast related bone dysplasia. The presence of genetic anomalies was associated with longer in-situ time of the implant. Our findings warrant the need of similar studies in larger patient cohorts to evaluate the risk of development of neoplastic alterations in periprosthetic tissues of patients with MoM hip replacement.

Monosomy of chromosome 17 in breast cancer during interpretation of HER2 gene amplification.

Monosomy of chromosome 17 may affect the assessment of HER2 amplification. Notably, the prevalence ranges from 1% up to 49% due to lack of consensus in recognition. We sought to investigate the impact of monosomy of chromosome 17 to interpretation of HER2 gene status. 201 breast carcinoma were reviewed for HER2 gene amplification and chromosome 17 status. FISH analysis was performed by using double probes (LSI/CEP). Absolute gene copy number was also scored per each probe. HER2 FISH test was repeated on serial tissue sections, ranging in thickness from 3 to 20 µm. Ratio was scored and subsequently corrected by monosomy after gold control test using the aCGH method to overcome false interpretation due to artefactual nuclear truncation. HER2 immunotests was performed on all cases. 26/201 cases were amplified (13%). Single signals per CEP17 were revealed in 7/201 (3.5%) cases. Five out of 7 cases appeared monosomic with aCGH (overall, 5/201, 2.5%) and evidenced single signals in >60% of nuclei after second-look on FISH when matching both techniques. Among 5, one case showed amplification with a pattern 7/1 (HER2/CEP17>2) of copies (3+ at immunotest); three cases revealed single signals per both probes (LSI/CEP=1) and one case revealed a 3:1 ratio; all last 4 cases showed 0/1+ immunoscore. We concluded that: 1) monosomy of chromosome 17 may be observed in 2.5% of breast carcinoma; 2) monosomy of chromosome 17 due to biological reasons rather than nuclear truncation was observed when using the cut-off of 60% of nuclei harboring single signals; 3) the skewing of the ratio due to single centromeric 17 probe may lead to false positive evaluation; 4) breast carcinomas showing a 3:1 ratio (HER2/CEP17) usually show negative 0/1+ immunoscore and <6 gene copy number at FISH.

ALK fusion and its association with other driver gene mutations in Finnish non-small cell lung cancer patients.

Screening of anaplastic lymphoma tyrosine kinase (ALK) gene fusions in non-small cell lung cancer (NSCLC) patients enables the identification of the patients likely to benefit from ALK-targeted therapy. Our aim was to assess the prevalence of ALK fusion in Finnish NSCLC patients, which has not been reported earlier, and to study the presence of ALK fusion in relation to clinicopathological characteristics and other driver gene mutations. A total of 469 formalin-fixed paraffin-embedded tumor tissue specimens from Finnish NSCLC patients were screened for ALK fusion by immunohistochemistry (IHC). For confirmation of IHC results, fluorescence in situ hybridization (FISH) was conducted for 171 specimens. Next-generation sequencing was performed for all ALK-positive specimens to characterize the association of ALK fusion with mutations in targeted regions of 22 driver genes. Of the 469 tumors screened, 11 (2.3%) harbored an ALK fusion, including nine adenocarcinomas and two large cell carcinomas. The IHC results for all 11 ALK-positive and 160 random ALK-negative specimens were confirmed by FISH. ALK fusion was significantly associated with never/ex-light smoking history (P<0.001) and younger age (P=0.004). Seven ALK-positive tumors showed additional mutations; three in MET, one in MET and CTNNB1, two in TP53, and one in PIK3CA. Our results show that ALK fusion is an infrequent alteration in Finnish NSCLC patients. Although the majority of ALK-positive cases were adenocarcinomas, the fusion was also seen in large cell carcinomas. Further studies are needed to elucidate the clinical significance of the coexistence of ALK fusion with MET, TP53, CTNNB1, and PIK3CA mutations.