This case-sensitive code system http://fhir.ch/ig/ch-crl/CodeSystem/nkrs-icdo3laterality defines the following codes:

Code	Display	Definition
1	Right
2	Left
3	Unilateral, NOS	Unilateral, but unknown whether right or left.
4	Bilateral	Origin of primary tumour is on both sides of a paired organ (when tumours of the same morphology are diagnosed simultaneously in both sides of a paired organ). Bilateral cancers are very rare, e.g. bilateral retinoblastoma, bilateral Wilms tumour of the kidney, or both ovaries involved simultaneously.