Expression of alpha smooth muscle actin (alpha-sma) in small bronchioloalveolar adenocarcinoma of the lung: assessment and comparison with noguchi's criteria.

M Sato, MD,a Y Ozeki, MD,a S Aida, MD,a Y Ohshika, MD,a H Hashimoto, MD,a H Obara, MD,a T Ogata, MD,b T Maehara, MD,a

aSurgery 2 and Pathology Division, National Defense Medical College, Tokorozawa, Saitama, Japan, bHealth Examination Center, School of Medicine, Tokai University, Kanagawa, Japan.

Aim Recently, the criterion advocated by Noguchi et al. is useful in assessing the prognosis of small lung adenocarcinomas. Now, we examined the expression of alpha-SMA, which is produced by the active fibroblasts (myofibroblasts), in the stroma of bronchioloalveolar adenocarcinoma by immunohistochemical staining to determine the clinicopathological characteristics of small bronchioloalveolar adenocarcinomas, and compared its expression with Noguchi's classification. Methods Twenty five cases, which are the lung bronchioloalveolar adenocarcinomas less than 2cm in size and thought to be Types A, B and C by Noguchifs criteria, were immunohistochemically examined with the antibody to alpha-SMA. More than 10% staining is considered to be positive. Results Of the 25 cases, 11 cases showed positive staining for alpha-SMA and 14 cases negative, whereas no positive cases were seen in Type A or B by Noguchifs criteria. In the positive cases, vascular and lymph nodes involvement were many more than in negative cases and the positive cases showed poorer prognosis. In 2 (18.2%) of 11 positive cases, distant metastases were recognized but negative cases (n=14) for alpha-SMA expression had no metastasis. Conclusions Immunohistochemical detection of alpha-SMA is more useful than Noguchi's classification because of the distinguishable the histological type B from C by Noguchifs criteria, and moreover the expression of alpha-SMA in the stroma of lung bronchioloalveolar adenocarcinoma is a significant prognostic factor.

KEY WORDS: myofibroblast, activation of fibroblast, prognostic factors.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Metastasis.