I wonder how frequently the use of topical fluorouracil cream results in permanent scarring and/or skin discoloration (e.g., hyper- or hypopigmentation).
What I have found so far doesn't give any source supporting their claims and is sometimes contradictory:
Uncommon (0.1–1% frequency):
- hyper- or hypopigmentation
They give 2 references (""):
- : Rossi, S, ed. (2013). Australian Medicines Handbook (2013 ed.). Adelaide: The Australian Medicines Handbook Unit Trust. ISBN 978-0-9805790-9-3.
- : "Efudex, Carac (fluorouracil topical) dosing, indications, interactions, adverse effects, and more". Medscape Reference. WebMD. Archived from the original on 2 February 2014. Retrieved 24 January 2014.
But I don't have access to  and the reference  only says:
- Hyperpigmentation (rare)
- Scarring (rare)"
without any references and precise frequency numbers ("rare" can mean anything from >0 to ~20%).
I also found on http://chemocare.com/chemotherapy/drug-info/fluorouracil.aspx:
These side effects are less common side effects (occurring in about 10-29%) of patients receiving Fluorouracil:
- Skin reactions : Dry, cracking, peeling skin. Darkening of the skin (hyperpigmentation), darkening of the skin where previous radiation treatment has been given (radiation recall).
How frequently does the use of topical fluorouracil cream (e.g., to treat a superficial basal cell carcinoma (BCC)) result in permanent scarring and/or skin discoloration? I'm looking for a percentage from some study instead of a vague, unsupported "rare", "sometimes", etc. that the quotes above give.