Coexistence of lactating adenoma and invasive ductal adenocarcinoma of the breast in a pregnant woman

Abstract

A 36 year old pregnant woman was admitted to hospital complaining of an enlarging mass in her left breast. Histopathological examination of the mastectomy specimen revealed a high grade infiltrating ductal adenocarcinoma intermixed with a lactating adenoma. Lactating adenomas are rare entities but are the most common masses that occur during pregnancy. Although they are not thought to carry an increased risk of cancer there are two other case reports in the literature of a lactating adenoma associated with an infiltrating carcinoma. In this case, areas where the lactating adenoma and the infiltrating carcinoma were intermixed could be identified. This case could simply be a collision tumour, although the possibility of an invasive carcinoma arising within a lactating adenoma cannot be ruled out. Because of the relative lack of experience with lactating adenomas, the question of an increased association with carcinoma development remains unclear.

Figure 1

(A) Gross photograph showing cream coloured tumour at the top (the central cystic haemorrhagic area is the result of a previous biopsy) merging with a lactating adenoma at the bottom. (B) The lactating adenoma is well circumscribed and characterised by ducts lined with vacuolated secretory cells. (C) High power magnification of the infiltrating adenocarcinoma demonstrating its high grade nature. (D) Low power magnification showing an invasive carcinoma displaying mixed morphology infiltrating between the lobules of the lactating adenoma.

Figure 2

(A) Invasive carcinoma infiltrating within the lactating adenoma. (B) Lobules harbouring both tubular adenoma and infiltrative carcinoma. (C) Lobular cancerisation. (D) Foci of high grade ductal carcinoma in situ between the lobules of the lactating adenoma.