Genomic heterogeneity of ALK fusion breakpoints in non-small-cell lung cancer.

In lung adenocarcinoma, canonical EML4-ALK inversion results in a fusion protein with a constitutively active ALK kinase domain. Evidence of ALK rearrangement occurs in a minority (2-7%) of lung adenocarcinoma, and only ~60% of these patients will respond to targeted ALK inhibition by drugs such as crizotinib and ceritinib. Clinically, targeted anti-ALK therapy is often initiated based on evidence of an ALK genomic rearrangement detected by fluorescence in situ hybridization (FISH) of interphase cells in formalin-fixed, paraffin-embedded tissue sections. At the genomic level, however, ALK rearrangements are heterogeneous, with multiple potential breakpoints in EML4, and alternate fusion partners. Using next-generation sequencing of DNA and RNA together with ALK immunohistochemistry, we comprehensively characterized genomic breakpoints in 33 FISH-positive lung adenocarcinomas. Of these 33 cases, 29 (88%) had detectable DNA level ALK rearrangements involving EML4, KIF5B, or non-canonical partners including ASXL2, ATP6V1B1, PRKAR1A, and SPDYA. A subset of 12 cases had material available for RNA-Seq. Of these, eight of eight (100%) cases with DNA rearrangements showed ALK fusion transcripts from RNA-Seq; three of four cases (75%) without detectable DNA rearrangements were similarly negative by RNA-Seq, and one case was positive by RNA-Seq but negative by DNA next-generation sequencing. By immunohistochemistry, 17 of 19 (89%) tested cases were clearly positive for ALK protein expression; the remaining cases had no detectable DNA level rearrangement or had a non-canonical rearrangement not predicted to form a fusion protein. Survival analysis of patients treated with targeted ALK inhibitors demonstrates a significant difference in mean survival between patients with next-generation sequencing confirmed EML4-ALK rearrangements, and those without (20.6 months vs 5.4 months, P<0.01). Together, these data demonstrate abundant genomic heterogeneity among ALK-rearranged lung adenocarcinoma, which may account for differences in treatment response with targeted ALK inhibitors.

Gastrointestinal lymphomas in a North American population: clinicopathologic features from one major Central-Midwestern United States tertiary care medical center.

BACKGROUND: Gastrointestinal (GI) lymphomas are very common types of extranodal lymphomas, and we hypothesize there are regional differences in subtype, distribution in the GI tract, and epidemiological features among the different populations. METHODS: We retrospectively evaluated the clinical, molecular and histologic features of North American primary and secondary GI lymphomas diagnosed from 2000-2009 seen at our institution. We utilized immunohistochemistry and fluorescence in situ hybridization to further evaluate a subset of the gastric lymphomas. RESULTS: Extranodal marginal zone lymphomas of mucosal associated lymphoid tissue (MALTs) and diffuse large B cell lymphomas (DLBCLs) were the most common subtypes of GI lymphomas. Select gastric DLBCLs (N = 6) and MALTs (N = 13) were further examined for API2-MALT1 and IGH translocations, and P16 and P53 protein expression. Gastric MALTs showed frequent API2-MALT1 (38%) but not IGH translocations (0%), and the DLBCLs showed neither translocation. Expression of P16 and P53 proteins and the proliferative index were compared between high grade gastric lymphomas (gastric DLBCLs) and low grade gastric lymphomas (gastric MALTs). P53 overexpression (P = 0.008) and a high proliferation index [Ki-67] (P = 0.00042) were significantly associated with gastric DLBCL, but no statistically significant difference was observed in P16 expression (p = 0.108) between gastric DLBCL and gastric MALT. CONCLUSION: Our study revealed that GI lymphomas from a Central-Midwestern North American population showed differences and similarities to non-North American cohorts. In addition, API2-MALT1, P16 and P53 abnormalities occurred frequently in gastric lymphomas from this North American population. VIRTUAL SLIDES: The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1415505838687793.

Anaplastic meningioma arising from a radiologically diagnosed arachnoid cyst: case report.

OBJECTIVE AND IMPORTANCE: We report the first example of an anaplastic meningioma arising from an intracranial arachnoid cyst and discuss the diagnostic challenges of this case, including the useful role of genetic markers. CLINICAL PRESENTATION: A 72-year-old man presented with transient episodes of expressive dysphasia and focal motor seizures, superimposed on a 6-month history of worsening headaches and dizziness. His past history was significant for a previously drained left-sided chronic subdural hematoma and a radiologically diagnosed left middle fossa arachnoid cyst. Magnetic resonance imaging on admission showed variable wall thickening of the arachnoid cyst with mild mass effect on the left frontotemporal lobes. INTERVENTION: The patient underwent decompression of the arachnoid cyst and biopsy of the cyst wall. Histologic and immunohistochemical studies of the thickened portion initially suggested a metastatic carcinosarcoma, but fluorescence in situ hybridization (FISH) studies confirmed the diagnosis of anaplastic meningioma based on characteristic chromosomal deletions. The patient returned 2 months later with progressive disease, leading to his death 6 weeks later despite repeat surgery for tumor debulking. CONCLUSION: Malignant transformation of meningothelial elements in arachnoid cysts is an exceptionally rare complication that poses considerable diagnostic challenges. Genetic markers may be particularly helpful in such cases.

Transcriptomic versus chromosomal prognostic markers and clinical outcome in uveal melanoma.

PURPOSE: To compare a gene expression-based classifier versus the standard genetic prognostic marker, monosomy 3, for predicting metastasis in uveal melanoma. EXPERIMENTAL DESIGN: Gene expression profiling, fluorescence in situ hybridization (FISH), and array comparative genomic hybridization (aCGH) were done on 67 primary uveal melanomas. Clinical and pathologic prognostic factors were also assessed. Variables were analyzed by Cox proportional hazards, Kaplan-Meier analysis, sensitivity, specificity, positive and negative predictive value, and positive and negative likelihood ratios. RESULTS: The gene expression-based molecular classifier assigned 27 tumors to class 1 (low risk) and 25 tumors to class 2 (high risk). By Cox univariate proportional hazards, class 2 signature (P = 0.0001), advanced patient age (P = 0.01), and scleral invasion (P = 0.007) were the only variables significantly associated with metastasis. Only the class 2 signature was needed to optimize predictive accuracy in a Cox multivariate model. A less significant association with metastasis was observed for monosomy 3 detected by aCGH (P = 0.076) and FISH (P = 0.127). The sensitivity and specificity for the molecular classifier (84.6% and 92.9%, respectively) were superior to monosomy 3 detected by aCGH (58.3% and 85.7%, respectively) and FISH (50.0% and 72.7%, respectively). Positive and negative predictive values (91.7% and 86.7%, respectively) and positive and negative likelihood ratios (11.9 and 0.2, respectively) for the molecular classifier were also superior to those for monosomy 3. CONCLUSIONS: Molecular classification based on gene expression profiling of the primary tumor was superior to monosomy 3 and clinicopathologic prognostic factors for predicting metastasis in uveal melanoma.