---
kind: "section"
citation: "42 C.F.R. § 81.23"
title: "42"
number: "81.23"
heading: "Guidelines for cancers for which primary site is unknown."
url: "https://uscodex.org/cfr/42/81.23"
---

# §81.23. Guidelines for cancers for which primary site is unknown.

- (a) In claims for which the primary cancer site cannot be determined, but a site of metastasis is known, DOL will calculate probability of causation estimates for various likely primary sites. Table 1 of this [paragraph (a)](#a) indicates the primary cancer site(s) DOL will use in NIOSH-IREP when the primary cancer site is unknown.
- (b) DOL will select the site producing the highest estimate for probability of causation to adjudicate the claim.

## Notes

### Amendments

[67 FR 22309, May 2, 2002, as amended at 84 FR 37590, Aug. 1, 2019]

### Authority

Authority: 42 U.S.C. 7384n(c); E.O. 13179, 65 FR 77487, 3 CFR, 2000 Comp., p. 321.

### Source

Source: 67 FR 22309, May 2, 2002, unless otherwise noted.

### Amendments

[67 FR 22309, May 2, 2002, as amended at 84 FR 37590, Aug. 1, 2019]