Table 1.

Definitions of various chromosome 1 abnormalities.

+1q†	Additional copies of any part of the long arm of chromosome 1(1q), irrespective of copy number or segment of DNA that is gained
Gain(1q)†	Gain of only 1 extra copy of chromosome 1q (3 total copies)
Amp(1q)†	“Amplification” of 1q, with at least 2 extra copies of chromosome 1q (4 or more total copies)
Trisomy 1	Gain of both arms of chromosome 1, including 1p
C1A	“Chromosome 1 abnormality”, including any abnormal signal(s) in 1q and/or 1p

^†In MM, 1q is frequently expanded to 1q21, a more specific denotation that specifies region 2, band 1 on the long arm of chromosome 1. The FISH probe used for this region is most commonly CKS1B, and is reported as “nuc ish CKS1BxN”, with “N” denoting the number of signals (i.e., copies) seen using the CKS1B probe.