Utility of 18F-FDG-PET/CT in patients suspected of paraneoplastic neurological syndrome: importance of risk classification.

PURPOSE: To assess the diagnostic impact of 18F-FDG-PET/CT in patients suspected of paraneoplastic neurological syndrome (PNS) based on our own pre-test risk classification (PRC). METHODS: A multicenter retrospective longitudinal study was conducted from 2006 to 2014. We designed a seven-point scoring system using the clinical syndrome characteristics [classical (CS) and non-classical syndromes (NCS)] and its location (central, peripheral, in the neuromuscular junction or combined), onconeural antibodies and tumor markers. Patients were classified as low (score 0-2), intermediate (3-4) and high (5-7) pre-test risk of PNS. FDG-PET/CT was classified as negative or positive. Final diagnosis according Graus' criteria (definite, possible or no PNS) was established. Relations between clinical and metabolic variables with the final diagnosis were studied. RESULTS: 73 patients were included, with a follow-up time of 33 months. Eleven (15 %) patients were finally diagnosed with neoplasm (8 invasive cancers). Ultimately, 13 (18 %) and 24 (33 %) subjects were diagnosed as definite or possible PNS. All the patients with final diagnosis of neoplasm had a CS (p = 0.005). PET/CT was helpful to diagnose 6/8 (75 %) invasive cancers. PET/CT findings were associated with the final diagnosis of neoplasm (p = 0.003) and the diagnosis of PNS attending to Graus' criteria (p = 0.019). PRC showed significant association with the final diagnosis of neoplasm and PET/CT results. A majority of patients (10/11) diagnosed of neoplasm had intermediate/high-risk. CONCLUSIONS: Our PRC seems to be a valid tool to select candidates for PET/CT imaging in this setting. PET/CT detected malignancy in a significant proportion of patients with invasive cancer.

Genetic drift or natural selection? Hybridization and asymmetric mitochondrial introgression in two Caribbean lizards (Anolis pulchellus and Anolis krugi).

Hybridization and gene introgression can occur frequently between closely related taxa, but appear to be rare phenomena among members of the species-rich West Indian radiation of Anolis lizards. We investigated the pattern and possible mechanism of introgression between two sister species from Puerto Rico, Anolis pulchellus and Anolis krugi, using mitochondrial (ND2) and nuclear (DNAH3, NKTR) DNA sequences. Our findings demonstrated extensive introgression of A. krugi mtDNA (k-mtDNA) into the genome of A. pulchellus in western Puerto Rico, to the extent that k-mtDNA has mostly or completely replaced the native mtDNA of A. pulchellus on this part of the island. We proposed two not mutually exclusive scenarios to account for the interspecific matings between A. pulchellus and A. krugi. We inferred that hybridization events occurred independently in several populations, and determined that k-mtDNA haplotypes harboured in individuals of A. pulchellus can be assigned to four of the five major mtDNA clades of A. krugi. Further, the spatial distribution of k-mtDNA clades in the two species is largely congruent. Based on this evidence, we concluded that natural selection was the probable driving mechanism for the extensive k-mtDNA introgression into A. pulchellus. Our two nuclear data sets yielded different results. DNAH3 showed reciprocal monophyly of A. pulchellus and A. krugi, indicating no effect of hybridization on this marker. In contrast, the two species shared nine NKTR alleles, probably due to incomplete lineage sorting. Our study system will provide an excellent opportunity to experimentally assess the behavioural and ecological mechanisms that can lead to hybridization in closely related taxa.

Molecular systematics of new world gopher, bull, and pinesnakes (Pituophis: Colubridae), a transcontinental species complex.

Pituophis melanoleucus (gopher, bull, and pinesnakes) is among the most widely distributed polytypic species complexes in North America, with most authors recognizing from a single transcontinental species (the melanoleucus complex, composed of 15 subspecies) to four (monotypic and polytypic) species. We used mitochondrial gene sequences from the two middle American species, P. deppei and P. lineaticollis, and from 13 subspecies from most of the range of the melanoleucus complex to test various phylogenetic hypotheses for Pituophis. Maximum parsimony and maximum likelihood methods identified the same major clades within Pituophis and indicated that two segments of the melanoleucus complex, the lodingi-melanoleucus-mugitus eastern pinesnake clade and the affinis-annectens-bimaris-catenifer-deserticola- sayi-ruthveni-vertebr alis clade from central and western United States and northern Mexico, represent divergent, allopatric lineages with no known intergradation zone. We recognize each of these two groupings as a different species. Our data also indicate that some ruthveni are more closely related to sayi than to other ruthveni. Nonetheless, ruthveni is an allopatric taxon diagnosable from its closest relatives by a combination of morphometric characters, and because it is likely that at least some of these traits are independent and genetically inherited, we interpret this as evidence that ruthveni has attained the status of independent evolutionary lineage, despite the fact that it retains strong genetic affinities with sayi. The endemic Baja Californian gopher snakes (bimaris and vertebralis) are considered by some taxonomists as a different species, P. vertebralis, but we discovered that these serpents belong to two different clades and hence we do not agree with the recognition of P. vertebralis as presently defined. In summary, we believe that three distinct species are included in the melanoleucus complex, Pituophis melanoleucus (sensu stricto), P. catenifer, and P. ruthveni, and that their recognition better represents the evolutionary diversity within this species complex.