Purpose: Small cell neuroendocrine carcinoma of the prostate is likely to become increasingly common with recent advances in pharmacologic androgen suppression. Thus, developing molecular markers of small cell differentiation in prostate cancer will be important to guide the diagnosis and therapy of this aggressive tumor.Experimental Design: We examined the status of RB1, TP53, and PTEN in prostatic small cell and acinar carcinomas via immunohistochemistry (IHC), copy-number alteration analysis, and sequencing of formalin-fixed paraffin-embedded specimens.Results: We found retinoblastoma (Rb) protein loss in 90% of small cell carcinoma cases (26 of 29) with RB1 allelic loss in 85% of cases (11 of 13). Of acinar tumors occurring concurrently with prostatic small cell carcinoma, 43% (3 of 7) showed Rb protein loss. In contrast, only 7% of primary high-grade acinar carcinomas (10 of 150), 11% of primary acinar carcinomas with neuroendocrine differentiation (4 of 35), and 15% of metastatic castrate-resistant acinar carcinomas (2 of 13) showed Rb protein loss. Loss of PTEN protein was seen in 63% of small cell carcinomas (17 of 27), with 38% (5 of 13) showing allelic loss. By IHC, accumulation of p53 was observed in 56% of small cell carcinomas (14 of 25), with 60% of cases (6 of 10) showing TP53 mutation.Conclusions: Loss of RB1 by deletion is a common event in prostatic small cell carcinoma and can be detected by a validated IHC assay. As Rb protein loss rarely occurs in high-grade acinar tumors, these data suggest that Rb loss is a critical event in the development of small cell carcinomas and may be a useful diagnostic and potential therapeutic target. Clin Cancer Res; 20(4); 890-903. Ó2013 AACR.

Rare, generally pediatric oligodendroglioma-like neoplasms with extensive leptomeningeal dissemination have been interpreted variably as glial, oligodendroglial or glioneuronal. The clinicopathologic features have not been fully characterized. We studied 36 patients, 12 females and 24 males with a median age of 5 years (range 5 months-46 years). MRI demonstrated leptomeningeal enhancement, frequently with cystic or nodular T2 hyperintense lesions within the spinal cord/brain along the subpial surface. A discrete intraparenchymal lesion, usually in the spinal cord, was found in 25 (of 31) (81 %). Tumors contained oligodendroglioma-like cells with low-mitotic activity (median 0 per 10 high power fields, range 0-4), and rare ganglion/ganglioid cells in 6 cases (17 %). Tumors were mostly low-grade, with anaplastic progression in 8 (22 %). Immunohistochemistry demonstrated strong reactivity for OLIG2 (7 of 9) (78 %), and moderate/strong S100 (11 of 12) (92 %), GFAP (12 of 31) (39 %) and synaptophysin (19 of 27) (70 %). NeuN, EMA, and mutant IDH1 (R132H) protein were negative. Median MIB1 labeling index was 1.5 % (range <1-30 %). FISH (n = 13) or SNP array (n = 2) demonstrated 1p loss/intact 19q in 8 (53 %), 1p19q co-deletion in 3 (20 %), and no 1p or 19q loss in 4 (27 %). Clinical follow-up (n = 24) generally showed periods of stability or slow progression, but a subset of tumors progressed to anaplasia and behaved more aggressively. Nine patients (38 %) died 3 months-21 years after diagnosis (median total follow-up 5 years). We report a series of a neoplasm with distinct clinicopathologic and molecular features. Although most progress slowly, a significant fraction develop aggressive features.

Objectives To validate next-generation sequencing (NGS) technology for clinical diagnosis and to determine appropriate read depth. Methods We validated the KRAS, BRAF, and EGFR genes within the Ion AmpliSeq Cancer Hotspot Panel using the Ion Torrent Personal Genome Machine (Life Technologies, Carlsbad, CA). Results We developed a statistical model to determine the read depth needed for a given percent tumor cellularity and number of functional genomes. Bottlenecking can result from too few input genomes. By using 16 formalin-fixed, paraffin-embedded (FFPE) cancer-free specimens and 118 cancer specimens with known mutation status, we validated the six traditional analytic performance characteristics recommended by the Next-Generation Sequencing: Standardization of Clinical Testing Working Group. Baseline noise is consistent with spontaneous and FFPE-induced C:G→T:A deamination mutations. Conclusions Redundant bioinformatic pipelines are essential, since a single analysis pipeline gave false-negative and false-positive results. NGS is sufficiently robust for the clinical detection of gene mutations, with attention to potential artifacts.