[177] Neuroendocrine Cell Hyperplasia of the Breast – Potential Precancerous Lesion of Mammary Neuroendocrine Carcinoma

Tomonori Kawasaki, Kunio Mochizuki, Tetsuo Kondo, Hideko Yamauchi, Shingo Inoue, Masayuki Inoue, Naoki Oishi, Tetsu Yamane, Tadao Nakazawa, Dongfeng Niu, Kumiko Nakazawa, Yoshio Ishii, Tsutomu Yuminamochi, Hiroshi Yagata, Hiroko Tsunoda, Hiroshi Onishi, Hideki Fujii, Ryohei Katoh. University of Yamanashi, Yamanashi, Japan; St. Luke's International Hospital, Tokyo, Japan

Background: The World Health Organization (WHO) classifies breast neuroendocrine carcinoma (B-NEC), defined as >50% neoplastic cells expressing specific NE markers, as a special tumor entity representing only about 2-5% of mammary cancers. However, the natural history of B-NEC and the mechanisms underlying its development have yet to be sufficiently analyzed and established.
Design: To clarify the presence of a precursor lesion of B-NEC, we investigated 32 totally-resected mammary tissues with a B-NEC using an immunohistochemical technique with primary antibodies against chromogranin A (CgA) and synaptophysin (Syn). Thirty-two mastectomy specimens harboring a mammary non-NE carcinoma were also examined in the same fashion.
Results: The 32 B-NECs were histologically subclassified into NE ductal carcinoma in situ (NE-DCIS) (7 cases, 22%), solid NEC (16 cases, 50%), mucinous NEC (3 cases, 9%), small cell NEC (1case, 3%) and large cell NEC (5 cases, 16%). NE cell hyperplasia, demonstrated by immunohistochemistry for CgA and/or Syn, was widely identified in background mammary ducts and lobules of the 7 B-NECs (22%): 3 NE-DCISs and 4 solid NECs. NE cell hyperplasia showed isolated (Fig. A: Syn), scattered (Fig. B: CgA), clustered (Fig. C: Syn) and/or circumferential (Fig. D: CgA) emerging patterns.

These NE cells were morphologically polygonal, ovoid or columnar with faintly fine-granular cytoplasm and round-to-oval nuclei without atypism. With the exception of a clustered pattern, NE cells were not readily recognizable by hematoxylin and eosin staining. Furthermore, 4 of 7 cases with NE cell hyperplasia had multifocal B-NEC. In contrast, 32 non-NE carcinomas had no NE cells in the cancer lesion background.
Conclusions: This report is the first to describe NE cell hyperplasia which could be regarded as a precancerous lesion closely related to the malignant progression of B-NEC. A background of extensive NE cell hyperplasia should be taken into consideration when treating B-NEC.
Category: Breast

Monday, March 19, 2012 1:00 PM

Poster Session II # 49, Monday Afternoon

 

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