Elsevier

The Lancet

Volume 353, Issue 9166, 22 May 1999, Pages 1742-1745
The Lancet

Articles
Risk of breast cancer in women with palpable breast cysts: a prospective study

https://doi.org/10.1016/S0140-6736(98)06408-3Get rights and content

Summary

Background

7% of women in the western world develop palpable breast cysts. Studies of the relation between cysts and breast cancer have conflicting results. There are two clearly defined types of cyst. We investigated whether one cyst type is associated with a higher rate of breast-cancer development than the other.

Methods

We studied 1374 women with palpable breast cysts presenting between 1981 and 1987, who had cysts aspirated between 1981 and 1989. Cysts were classified as type I if the sodium/potassium (Na+/K+) ratio in the cyst fluid was less than 3, or type II if the Na+/K+ ratio was 3 or more. Data on incidence of breast cancer were available until January, 1995, and we compared them with the expected numbers of cancers calculated from age-specific breast-cancer incidence in Scotland in 1988.

Findings

65 cancers developed during follow-up. The overall standardised incidence rate of breast cancer in patients with palpable cysts was 2·81 (95% Cl 2·17–3·59). The relative incidence rate was increased for all cyst types. The standardised incidence rate of developing breast cancer among women younger than 45 years was highest at 5·94 (2·97–10·63), with a significant trend for decreasing relative incidence rate with age (p<0·05). Women older than 54 years had a standardised incidence rate of 1·73 (0·86–3·10). The standardised incidence rate of breast cancer was highest in the first year after aspiration (7·02 [3·73–12·00]) but the risk was still raised after 5 years (2·68 [1·84–3·76]).

Interpretation

Women with breast cysts are at an increased risk of breast cancer, especiallly at younger ages. The type of cyst did not alter the associated relative incidence rate of breast-cancer development.

Introduction

Astley Cooper, in 1829, distinguished cysts from breast cancer.1 The first comprehensive clinical description of cystic disease was made more than 50 years later by Reclus2 and Brissaud.3 Reclus showed that microscopic cysts were commonly bilateral and could involve the whole gland.3 Microcysts are no longer thought to be pathological but are viewed as part of the normal involution process.4 Gross or palpable breast cysts are larger cysts that are thought to be aberrations of the normal process of involution and not a disease.4 Haagensen's estimate,5 based on the observation that gross cysts and breast cancer are seen with equal frequency, is that 7% of women in the western world develop palpable breast cysts.

The published evidence on the relation of palpable breast cysts (so-called cystic disease of the breast) and subsequent breast cancer is conflicting, mainly because definitions of cystic disease have differed. However, those studies that have included only or mainly patients with clinically palpable cysts have shown that these women are more likely than the general population to develop breast cancer.6, 7, 8, 9, 10, 11, 12, 13, 14

There are two clearly defined types of breast cysts.15, 16, 17, 18 Type I cysts are lined by apocrine epithelium and contain fluid with an electrolyte composition similar to that of intracellular fluid (high concentrations of potassium [K+], low concentrations of sodium (Na+), Na+/K+ ratio <3, and high concentrations of steroid hormones, including androsterone, epiandrosterone, and dehydroepiandrosterone, and their conjugates.16, 17, 19 Type II cysts are lined by flattened attenuated epithelium and contain fluid with an electrolyte composition similar to that of plasma (Na+/K+ ratio ≥3) and have lower concentrations of steroid hormones and their conjugates than type I cysts. The natural history of these two cyst types seems to differ; patients with type I cysts are more likely to develop further cysts than women with type II cysts, and patients who develop large numbers of cysts almost always have type I cysts.20 Histological risk factors for breast cancer have been reported to be more common with type I cysts21 and the few data available relating cyst type to breast-cancer risk have suggested that cancer might be more common in patients with such cysts.13, 14, 21

We aimed to assess prospectively in a large series of women with palpable breast cysts whether the risk of development of breast cancer was higher than in the normal population, and whether particular groups of women with cysts were at a higher risk of breast cancer than others.

Section snippets

Patients

1374 women with palpable breast cysts attending the Edinburgh Breast Unit in 1981–87 were studied. The Edinburgh Breast Unit is the only breast referral centre in Edinburgh and covers the population of Edinburgh, East and West Lothian, West Fife, and the Borders. This clinic is the first that patients attend and these 1374 women represented all new referrals with palpable cysts to the Unit during the study period. All patients had a full clinical assessment done by two doctors at the first

Results

74 invasive breast cancers developed in the study population. Seven of these developed before first cyst aspiration. From case notes and pathology records, two further patients were identified as having intracystic cancers. These nine patients were excluded from subsequent analyses and 65 cancers were analysed. Median follow-up was 5·0 years (range 0·04–12·4) in patients who developed cancer and 9·6 years (6·0–14·1) in those who did not.

The overall incidence of breast cancer in patients with

Discussion

Several studies have assessed the relation between palpable breast cysts and breast cancer. Early studies investigated the frequency with which breast cysts were found in breasts removed because of carcinoma.25 Since cystic disease affects a younger age-group than breast cancer, any cysts that precede breast cancer are likely to have disappeared by the time a cancer develops, and, therefore, any conclusions based on these studies are unreliable. Several authors have reported on series of

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