[Mammary metastasis of extramammary cancers: current knowledge and diagnostic difficulties]

Abstract

Objectives: Intramammary metastasis (IM) of non-breast cancers are infrequent. The purpose of this review of literature was to update the knowledge and explain diagnostic errors.

Patients and methods: A review of literature with PubMed was used to select 54 articles published in English between 2003 and 2012.

Results: Melanoma (138 cases, 29.8%) were more frequently responsible of 463 cases of MIM, followed by lung, gynecological, gastrointestinal and hematologic cancers. IM occur mainly in women (92.2%), around 50 years, and are metachronous (84.2%). Clinically, they are usually round, painless, without skin retraction and associated with adenopathies (33%). In imaging, they are frequently single. Diagnosis, sometimes evoked by morphological study of the tumor, is confirmed by immunohistochemistry. Systemic metastasis are common, involving a shorter survival.

Discussion: The prevalence of primitive cancers is not alone responsible for the frequency of IM, as we can observe it with melanoma. The "seed and soil" hypothesis of Paget may explain it: some tumor cells grow preferentially in selected organs. Vascularity of the breast also seems to be an important factor. Clinically, IM can be confused with benign tumors. However, a history of cancer and multiple lesions should raise the suspicion of malignancy. In imaging, signs are non-specific. The morphological characteristics do not confirm the diagnosis with certainty. Immuno-histochemistry is fundamental, as the comparison with the histology of primary tumor. Support is mainly palliative.

Keywords: Breast cancer; Cancer du sein; Extramammary cancer; Intramammary metastasis; Mammary tumours; Melanoma; Metastasis; Mélanome; Métastases; Métastases intra-mammaire; Tumeurs mammaires.