Clinicopathologic and molecular features of intracranial desmoplastic small round cell tumors.

Desmoplastic small round cell tumors (DSRCTs) are highly aggressive sarcomas that most commonly occur intra-abdominally, and are defined by EWSR1-WT1 gene fusion. Intracranial DSRCTs are exceptionally rare with only seven previously reported fusion-positive cases. Herein, we evaluate the clinical, morphologic, immunohistochemical and molecular features of five additional examples. All patients were male (age range 6-25 years; median 11 years), with four tumors located supratentorially and one within the posterior fossa. The histologic features were highly variable including small cell, embryonal, clear cell, rhabdoid, anaplastic and glioma-like appearances. A prominent desmoplastic stroma was seen in only two cases. The mitotic index ranged from <1 to 12/10 HPF (median 5). While all tumors showed strong desmin positivity, epithelial markers such as EMA, CAM 5.2 and other keratins were strongly positive in only one, focally positive in two and negative in two cases. EWSR1-WT1 gene fusion was present in all cases, with accompanying mutations in the TERT promoter or STAG2 gene in individual cases. Given the significant histologic diversity, in the absence of genetic evaluation these cases could easily be misinterpreted as other entities. Desmin immunostaining is a useful initial screening method for consideration of a DSRCT diagnosis, prompting confirmatory molecular testing. Demonstrating the presence of an EWSR1-WT1 fusion provides a definitive diagnosis of DSRCT. Genome-wide methylation profiles of intracranial DSRCTs matched those of extracranial DSRCTs. Thus, despite the occasionally unusual histologic features and immunoprofile, intracranial DSRCTs likely represent a similar, if not the same, entity as their soft tissue counterpart based on the shared fusion and methylation profiles.

Comparison of next-generation sequencing and mutation-specific platforms in clinical practice.

OBJECTIVES: To compare next-generation sequencing (NGS) platforms with mutation-specific analysis platforms in a clinical setting, in terms of sensitivity, mutation specificity, costs, capacity, and ease of use. METHODS: We analyzed 25 formalin-fixed, paraffin-embedded lung cancer samples of different size and tumor percentage for known KRAS and EGFR hotspot mutations with two dedicated genotyping platforms (cobas [Roche Diagnostics, Almere, The Netherlands] and Rotor-Gene [QIAGEN, Venlo, The Netherlands]) and two NGS platforms (454 Genome Sequencer [GS] junior [Roche Diagnostics] and Ion Torrent Personal Genome Machine [Life Technologies, Bleiswijk, The Netherlands]). RESULTS: All platforms, except the 454 GS junior, detected the mutations originally detected by Sanger sequencing and high-resolution melting prescreening and detected an additional KRAS mutation. The dedicated genotyping platforms outperformed the NGS platforms in speed and ease of use. The large sequencing capacity of the NGS platforms enabled them to deliver all mutation information for all samples at once. CONCLUSIONS: Sensitivity for detecting mutations was highly comparable among all platforms. The choice for either a dedicated genotyping platform or an NGS platform is basically a trade-off between speed and genetic information.

Simultaneous detection of clinically relevant mutations and amplifications for routine cancer pathology.

In routine cancer molecular pathology, various independent experiments are required to determine mutation and amplification status of clinically relevant genes. Most of these tests are designed to identify a limited number of genetic aberrations, most likely in a given tumor type. We present a modified version of a multiplexed PCR and IonTorrent-based sequencing approach that can replace a large number of existing assays. The test allows for the simultaneous detection of point mutations and gene amplifications in 40 genes, including known hotspot regions in oncogenes (KRAS, BRAF), inactivating mutations in tumor suppressors (TP53, PTEN), and oncogene amplifications (ERBB2, EGFR). All point mutations were confirmed using certified diagnostic assays, and a sensitivity and specificity of 100% (95% CI, 0.875-1.0) and 99% (95% CI, 0.960-0.999), respectively, were determined for amplifications in FFPE material. Implementation of a single assay to effectively detect mutations and amplifications in clinically relevant genes not only improves the efficiency of the workflow within diagnostic laboratories but also increases the chance of detecting (rare) actionable variants for a given tumor type that are typically missed in routine pathology. The ability to obtain comprehensive and rapid mutational overviews is key for improving the efficiency of cancer patient care through tailoring treatments based on the genetic characteristics of individual tumors.

Prognostic value of CTNNB1 gene mutation in primary sporadic aggressive fibromatosis.

BACKGROUND: Aggressive fibromatosis (AF) comprises tumors with a varying biological behavior. Genetic tumor characteristics may be predictive of recurrence; hence, the prognostic value of three specific mutations on the CTNNB1 gene was evaluated in relation to known clinicopathologic risk factors in patients with primary, sporadic AF. METHODS: In a multi-institutional retrospective cohort study of patients with primary extra-abdominal and abdominal wall AF who underwent surgical treatment, the original pathology specimens were reviewed for the presence of a T41A, S45F, and 45P mutations on the CTNNB1 gene. For these mutations, the risk of recurrence was analyzed by the Kaplan-Meier method with log-rank test. Univariable and multivariable Cox regression was performed to calculate hazard ratios. RESULTS: A total of 101 patients were analyzed. During a median follow-up of 41 months, 17 recurrences were detected; the cumulative 5-year recurrence rate was 22.8 %. A specific CTNNB1 mutation was found in 76 patients, with the majority of patients having a T41A mutation (n = 49). CTNNB1 mutations were associated with the risk of recurrence: the presence of a S45F mutation was associated with a 5-year cumulative risk of recurrence of 63.8 % (P < 0.001). Multivariable analysis showed that young age and S45F mutation were independent risk factors (P = 0.011 and P < 0.001). CONCLUSIONS: The presence of specific CTNNB1 mutations was predictive for recurrence in patients after surgical treatment for primary, sporadic extra-abdominal and abdominal AF. A S45F mutation increased the risk of recurrence significantly.