This can be used to help diagnose cancers of unknown primary origin, or to identify the origin of circulating tumor cells or DNA found in blood-based screens.
With respect to PM2.5 organic carbon, we know that particles of both primary and secondary origin are present in the airshed, and that the fraction of particles of primary origin tends to be greater near the urban core.
Metastasis is classically defined as the lymphatic or haematogenous (blood-born) dissemination of cancer cells from the primary tumor (origin) to lymph nodes and/or to distant sites in the body [1].
Metastasis of unknown primary origin is reported to occur in 3 4 % of all cancer patients and 10 15 % of them present with skeletal localizations [2, 13, 16, 17].
The median survival of high-risk patients with cancer of unknown primary origin ranges from 3 to 11 months, making prompt diagnosis and treatment very important [ 13- 15].
However, the documented relationship between single cell expression heterogeneity and plasticity of gene expression in response to perturbations [ 6] suggests that the primary origin of the increased response to signaling seen in U-CLL might be the higher heterogeneity present in this disease subtype.
Like the epidermis, the periderm is a protective tissue on the periphery of the plant body; however, because the periderm is produced by a lateral meristem, it is considered to be of secondary origin (in contrast to the primary origin of the epidermis from the protoderm).
The primary origin of data variation therefore appears to be related to biological differences between individual samples, which could be taken to reflect the variability in the expression of individual genes.
One can reasonably speculate that the three tumors we studied here were all in fact "secondary" to the primary origin of the tumor and metastases from the now obscured primary tumor, likely in the fallopian tube.
In contrast, the higher rates observed in the H1N1, H3N8 and H4N6 subtypes could be due to their primary origin as infections of wild birds with multiple low pathogenicity strains in the large avian reservoir.
