Cal. Bus. & Prof. Code § 1274

(a) A laboratory shall document to persons submitting cytologic samples for evaluation, on a quarterly basis, informational letters on all cases of HSIL (high-grade squamous intraepithelial lesions), adenocarcinoma, or other malignant neoplasm. Documentation may consist of followup correspondence, telephone calls, or requests included in the report. Copies of that documentation, and any responses received to those letters, shall be maintained on file by the laboratories for a period of five years.
(b) Whenever it becomes known to a clinical laboratory that an abnormality of HSIL (high-grade squamous intraepithelial lesions, adenocarcinoma, or other malignant neoplasm) has been identified for a patient for whom the clinical laboratory earlier reported a normal finding, all previous available cytologic slides on that patient shall be reexamined by the clinical laboratory.
(c) Records of the review of previous slides required by subdivision (b) shall be maintained by the clinical laboratory, including the name of the individual performing the earlier examination.
(d) A clinical laboratory shall maintain records of all false positive and false negative cases.
When any errors in the reporting of a smear evaluation are discovered, a corrected report shall be immediately sent, when medically applicable. Copies of corrected reports shall be maintained in the laboratory records for a period of 10 years.