a, Revisits of the same outgrowth in the non-cycling compartment. K14–H2BGFP labels epithelial nuclei (green). The non-hair cycling compartment is outlined in white. The cycling hair follicle, out of focal plane at later time points, is represented by a white dotted line. Insets show elimination of mutant core (tdTomato, red). b, Quantification of the phases of growth and regression of the outgrowths from the hair cycling epithelium of tamoxifen-treated (200 µg) Lgr6creER;β-catnflox(Ex3)/+;tdTomato;mTmG;K14–H2BGFP mice (mean ± s.e.m.). Pre-phenotypic plot accounts for hair follicles before the development of outgrowths to demonstrate variability in timing of formation (n = 33 outgrowths in three mice). c, Quantification of the two different fates of non-cycling epithelial outgrowths 173 days after induction (n = 24 outgrowths). d, Revisits from a tamoxifen-treated (200 µg) Lgr6creER;β-catnflox(Ex3)/+;tdTomato;mTmG;K14–H2BGFP mouse showing that, after the mutant core has differentiated out of the tissue (left), the remaining nodule of cells has converted into an extranumerary hair follicle. Subsequent revisits capture the representative extranumerary follicle in the early stage of catagen (centre) and telogen (right). e, Diagram representing the conversion into extranumerary structures. f, Revisits of representative Lgr6creER;β-catnflox(Ex3)/+;tdTomato;mTmG;K14–H2BGFP mouse after the administration of a high-dose (2 mg) of tamoxifen (n = 4 mice). Large benign tumours result in a macroscopic phenotype of severely wrinkled skin (day 21, left and inset) that resolves over time as the outgrowths regress (day 208, right and inset). g, Quantification of the hair follicles with tumours (mean ± s.e.m., n = 803 hair follicles across three mice). h, Quantification of hair follicles with supernumerary sebaceous gland lobes and de novo hair follicles after outgrowth regression (mean ± s.e.m., n = 580 hair follicles across three mice). i, Representative images of normal (left) and extranumerary (right) sebaceous glands present in the tissue 151 days after induction. Normal sebaceous glands are outlined in white, extranumerary structures are outlined in blue. j, Oil Red O staining on tail whole-mounts of Lgr6creER;β-catnflox(Ex3)/+ mouse 1 year after the administration of a high dose (2 mg) of tamoxifen. Note the Oil Red O staining in the extranumerary sebaceous gland lobes, indicating these structures are functional and actively producing lipids. k, Whole-mount Pcad IF staining on Lgr6creER;β-catnflox(Ex3)/+ ear skin 1 year after the administration of a high dose (2 mg) of tamoxifen, showing the extranumerary hair follicle has a Pcad enrichment at the base of the structure, similar to the hair germ of the main axis. All scale bars, 50 µm.