Craniopagus joined twins, as twins fused at their heads are known, are rare, estimated to occur once in 10 million births.
The incidence of decompression sickness is rare, estimated at 2.8 cases per 10,000 dives, with the risk 2.6 times greater for males than females.
CTCs are rare, estimated at one to ten tumor cells among ten billion normal blood cells in a milliliter of blood.
Further, cancer stem cells are very rare, estimated as 1 in 100,000 to 1,000,000 cancer cells in tumor tissue.
NSCLC mortality was assumed to occur only in the postdiagnosis stages of the disease under the assumption that all patients would be diagnosed with NSCLC before death since the incidence of lung cancer diagnosis at post mortem without clinical diagnosis is relatively rare (estimated to be <5% of the total incidence from the 2011 National Lung Cancer Audit Dataset (LUCADA)) (NHSIC, 2011).
While the risk of transmitting HIV or hepatitis C is now rare (estimated at 1 in 3 to 4 million transfusions), there is mounting evidence of adverse events associated with FP transfusions in particular (increased new onset lung injury) [ 4] and excess fluid administration in general in the critically ill [ 5, 6].
Although severe reactions to smallpox vaccines are relatively rare -- estimates of future reactions range from 1 in every 8,000 vaccinations to 1 in every 67,000 -- they are much more common in younger children.
Synesthesia is thought to be rare, but estimates are highly variable and unclear.
While not emphasized here, it is also important to consider whether adaptive evolution is rare and estimates of positive selection are inflated in other species (Fay 2011).
MODY is rare, with estimates of its prevalence between 0.3% and 2.4% of diabetes cases [ 3, 8– 11], although it is recognised that these figures represent underestimates.
