Invasive lobular carcinoma with extracellular mucin production—a novel pattern of lobular carcinomas of the breast. Clinico-pathological description of eight cases
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Invasive lobular carcinoma of the breast is known to produce intracellular mucin and has been recognized in single-case reports to show extracellular mucin production, as well. This latter morphology is not only rare but must also be under- or misdiagnosed. The aim was to better characterize this entity. Cases of lobular cancers demonstrating extracellular mucin formation were identified in a multi-institutional effort and their clinical and morphologic features were assessed. Immunohistochemistry was used to characterize the E-cadherin-membrane complex, neuroendocrine differentiation, and to some extent, mucin formation. All but one of the eight cases occurred in postmenopausal patients. Extracellular mucin production was present in 5 to 50% of the tumour samples and rarely also appeared in nodal and distant metastases. The tumours were completely E-cadherin negative and showed cytoplasmic p120 positivity. The majority (n = 6/8) was also completely negative for β-catenin, but two tumours displayed focal β-catenin positivity in the mucinous area. MUC1 and MUC2 expression was observed in all and 7/8 tumours, respectively; neuroendocrine differentiation was present in only one. Invasive lobular carcinoma with extracellular mucin formation is a rare morphologic variant of lobular carcinoma prone to be misdiagnosed and warranting further studies.
KeywordsBreast cancer E-cadherin Extracellular mucin Lobular carcinoma Mucinous carcinoma
The authors thank the help of Drs. Susanne Zöch and Sigurd Lax (Landeskrankenhaus Graz Süd-West, Graz, Austria); Dr. Vasiliki Zolota (University of Patras, Greece); Dr. Georgia Kafiri (Hippokrateio Hospital of Athens, Greece); Dr. Paivi Heikkila (University of Helsinki, Finland); Drs. Celia Perdaens and Veerle Delvaux (Jan Portaels Hospital, Vilvvorde, Belgium); and Dr. Janina Kulka (Semmelweis University, Budapest, Hungary) for their help in collecting the cases and or relevant clinical details. This study was partially funded by the National Research, Development and Innovation Office grant GINOP-2.3.2-15-2016-00020.
All authors of the manuscript made substantial contributions to the conception or design of the work; or the acquisition, analysis or interpretation of data for the work; and drafting the work and/or revising it critically for important intellectual content; and final approval of the version submitted for publication and agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Other contribution is acknowledged in the Acknowledgements section of the manuscript.
Compliance with ethical standards
The authors have consulted the journal policy regarding compliance with ethical standards and state that accepted principles of ethical and professional conduct have been followed. The authors include information regarding sources of funding and potential conflicts of interest (financial or non-financial). Ethical approval and informed consent related information (waiver for this particular study) are summarized in the final paragraph of the “Material and Methods”. The study did not include animals, therefore issues relating to animal welfare do not apply.
This study was partially funded by the National Research, Development and Innovation Office grant GINOP-2.3.2-15-2016-00020.
Conflict of interest
The authors declare that they have no conflict of interest.
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