As shown in Figure 1C, ALK rearrangements, indicated by two separated fluorescent signals (for example, orange and green signals indicated by a pair of arrows in the right panel) in a distance at least two signal diameters apart in a single nucleus, are detected in fusion-positive carcinoma (ALK+, right panel), but not (or less frequently in some cases) in fusion-negative carcinoma (ALK-, right panel). The gene discussed is ALK; the disease is carcinoma.