Pernicious anaemia and cancer risk in Denmark.

A cohort of 5072 patients with pernicious anaemia was identified in the Danish Hospital Discharge Register from 1977 to 1989 and, through linkage to the Danish Cancer Registry, the occurrence of cancer in the cohort was determined up to 1991. Observed numbers of cancer cases during 1-15 years of follow-up were compared with expected numbers based on national incidence rates. Besides the well-established increased risk for stomach cancer, the analysis also revealed a 2-fold increase in the relative risk for cancer of the buccal cavity and pharynx among pernicious anaemia patients in accordance with previous studies; previously reported elevated risks for other digestive tract cancers were not confirmed. There was a non-significantly increased risk for lymphatic and haematological malignancy but the risk tended to disappear after 5 years of follow-up, indicating a possible selection bias. Decreased risks for cervical cancer and non-melanoma skin cancer were also seen.