[Pulmonary adenocarcinoma with micropapillary pattern: a clinicopathologic and immunohistochemical study].

Objective: To study the clinicopathologic characteristics and immunohistochemical profile of lung adenocarcinomas with a micropapillary pattern (MPP).

Methods: Among 135 cases of lung adenocarcinomas, the clinical, histological and immunohistochemical features of 48 cases of lung adenocarcinomas with a micropapillary components (the micropapillary components > or = 10%) were studied. The literature was reviewed.

Results: All the 135 cases were resected pulmonary adenocarcinomas. Among 48 cases of lung adenocarcinomas with a micropapillary components, the age of patients ranged from 43 to 85 years (mean = 60.7 years). The male-to-female ratio was 9:7. Histologically, 36 cases of lung adenocarcinomas with the MPP were characterized by small papillary tufts lacking a central fibrovascular core lying freely within alveolar spaces (IA type) or in the clefts of fibrous tissue just like those in MPP breast cancers (IB type). Another type of the micropapillary pattern consisted of 12 cases, the micropapillary tufts floating within cystic spaces lined by tumor cells (II type). In micropapillary pattern-positive cases, lymphatic invasion and lymph node metastasis were identified significantly more frequently than in micropapillary pattern-negative cases (P < 0.01). The percentages of cases positive for various markers were 97.9% (47/48) for E-cadherin, 89.5% (43/48) for beta-catenin, 91.7% (44/48) for Muc-1, 70.8% (34/48) for epidermal growth factor receptor, 35.4% (17/48) for p53, 93.8% (45/48) for Ki-67. The percentages of cases with high expression (including 3+ or 4+) for these markers were 72.3% (34/47) for E-cadherin, 90.7% (39/43) for beta-catenin, 88.6% (39/44) for Muc-1, 52.8% (19/36) for epidermal growth factor receptor, 58.8% (10/17) for p53, 46.7% (16/36) for Ki-67. Adequate clinical follow-up information was available for 36 patients. The mean follow-up time was 21.1 months. Among these, 16 of 36 patients (44.4%) were alive with no evidence of tumor, 12(33.3%) were died, and 8 (22.2%) were alive with tumor.

Conclusion: Lung adenocarcinomas with the MPP correlates positively with lymphatic invasion and lymph node metastasis, and are likely to have a potential for high malignancy, suggesting a poor prognosis.