title: Stromal micropapillary pattern predominant lung adenocarcinoma--a report of two cases.
abstract: Generally, adenocarcinomas with micropapillary pattern, featuring small papillary tufts lacking a central fibrovascular core, are thought to have poor prognosis. This pattern has been described in various organs. However, tumor cells with micropapillary pattern of lung adenocarcinoma are more often seen to float within alveolar spaces (aerogenous micropapillary pattern, AMP) than in fibrotic stroma like other organs (stromal micropapillary pattern, SMP) and SMP predominant lung adenocarcinoma (SMPPLA) has not been well described yet. We presented two cases of SMPPLA which were found in the last four years. Both the cases showed more than 50% of SMP in the tumor area. The majority of the stromal micropapillary clusters expressed MUC1 and epithelial membrane antigen along the outer surface of cell membrane. On the other hand, connective tissues surrounding stromal micropapillary clusters showed no reactivity for epithelial markers (thyroid transcription factor-1 and cytokeratin) or endothelial marker (D2-40 and CD34). It means clusters of SMP do not exist within air space or lymphatic or vessel lumens. The tumors with SMP often presented lymphatic permeation and vessel invasion, and intriguingly, one of the two cases showed metastasis to the mediastinal lymph node. Additionally, both the cases showed EGFR point mutations of exon 21. These results suggest that SMPPLA might be associated with poor prognosis and effective for EGFR tyrosine kinase inhibitors.
authors.affiliation: Department of Pathology, Kanagawa Cancer Center, Kanagawa, Japan. ohem@kcch.jp
authors.forename: Miki
authors.initials: M
authors.lastname: Ohe
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Yokose
authors.forename: Yuji
authors.initials: Y
authors.lastname: Sakuma
authors.forename: Sachie
authors.initials: S
authors.lastname: Osanai
authors.forename: Chikako
authors.initials: C
authors.lastname: Hasegawa
authors.forename: Kota
authors.initials: K
authors.lastname: Washimi
authors.forename: Kimitoshi
authors.initials: K
authors.lastname: Nawa
authors.forename: Tetsukan
authors.initials: T
authors.lastname: Woo
authors.forename: Rurika
authors.initials: R
authors.lastname: Hamanaka
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Nakayama
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Kameda
authors.forename: Kouzo
authors.initials: K
authors.lastname: Yamada
authors.forename: Takeshi
authors.initials: T
authors.lastname: Isobe
mesh_terms: D000231:Adenocarcinoma, Papillary / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018773:Genes, erbB-1; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009367:Neoplasm Staging