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Int J Clin Exp Pathol 2013;6(11):2597-2602

Case Report
Mucinous bronchioloalveolar carcinoma with K-ras mutation arising in type 1 congenital
cystic adenomatoid malformation: a case report with review of the literature

Mitsuaki Ishida, Tomoyuki Igarashi, Koji Teramoto, Jun Hanaoka, Muneo Iwai, Keiko Yoshida, Akiko Kagotani, Noriaki Tezuka, Hidetoshi Okabe

Department of Clinical Laboratory Medicine and Division of Diagnostic Pathology, Department of Thoracic Surgery, Shiga University of Medical
Science, Shiga, Japan

Received August 22, 2013; Accepted September 15, 2013; Epub October 15, 2013; Published November 1, 2013

Abstract: Congenital cystic adenomatoid malformation (CCAM) of the lung is a rare hamartomatous cystic lesion, characterized by the
presence of large cysts, which are histopathologically lined by pseudostratified ciliated cells. It has been recognized that rare cases of type 1
CCAM show malignant transformation, usually bronchioloalveolar carcinoma (BAC) or adenocarcinoma. Herein, we describe a case of BAC
arising in type 1 CCAM with K-ras mutation. A 9-year-old Japanese girl presented with fever. Computed tomography demonstrated large cystic
lesions in her right lower lung. Histopathological study of the resected specimen revealed multiple cysts, which were lined by pseudostratified
ciliated cells, and occasionally interspersed with mucous cells without atypia. A small focus of proliferation of columnar cells showing lepidic
growth pattern was present. These columnar cells had abundant mucin in the cytoplasm and mildly to moderately enlarged nuclei. Accordingly,
a diagnosis of BAC arising in type 1 CCAM was made. Polymerase chain reaction analysis revealed K-ras mutation at codon 12 in the BAC
component. The presence of mucous cell/goblet cell hyperplasia and atypical adenomatous hyperplasia is a well known phenomenon in type
1 CCAM. A recent study clearly demonstrated K-ras mutation in these lesions, which are thought to be precursors of BAC. Therefore, the
concept of malignant transformation in the sequence from type 1 CCAM to mucous cell hyperplasia to atypical adenomatous hyperplasia to
BAC and invasive adenocarcinoma due to K-ras mutation has been proposed. Careful histopathological analysis is important for evaluation of
malignant lesions in type 1 CCAM. (IJCEP1308058).

Keywords: Congenital cystic adenomatoid malformation, mucinous bronchioloalveolar carcinoma, K-ras mutation

Address correspondence to: Dr. Mitsuaki Ishida, Department of Clinical Laboratory Medicine and Division of Diagnostic Pathology, Shiga
University of Medical Science, Tsukinowa-cho, Seta, Otsu, Shiga, 520-2192, Japan. Tel: +81-77-548-2603; Fax: +81-77-548-2407; E-mail:
mitsuaki@belle.shiga-med.ac.jp