[Fetal adenocarcinoma of the lung: a clinicopathologic analysis of six cases].

OBJECTIVE

To investigate the clinicopathologic features, diagnosis and differential diagnosis, and genetic alterations of fetal adenocarcinoma of lung (FACL).

METHODS

Six cases of FACL were collected from Fujian Provincial Hospital, the clinicopathologic features and immunophenotype were retrospectively evaluated, PAS/PASD staining and genetic mutation analysis of epidermal growth factor receptor (EGFR) were performed.

RESULTS

There were three male and three female patients, aged 40 to 75 years (median 59 years). Tumor size ranged from 2.5-6.0 cm (mean 3.8 cm). Histologically, the tumors showed classic glandular structure similar to fetal lung tubules. The neoplastic glands were lined by non-ciliated pseudostratified columnar epithelium with clear or granular cytoplasm. Some cells showed subnuclear or supranuclear vacuoles. Squamoid morules were also noted. Immunohistochemically, the tumor cells were positive for TTF1, Napsin A, CKL, and focally positive for CKH (2/6), synaptophysin (1/6), chromogranin A (1/6), CD56 (2/6), and EGFR (4/6). PAS/PASD staining was positive in the tumor cells. Five cases showed EGFR mutation, one case was of wild type. All six patients underwent surgical resection, and four had chemotherapy. All patients had no evidence of recurrence or metastasis during 1-40 months follow-up period.

CONCLUSIONS

FACL is a rare tumor with low malignant potential and has distinct morphologic feature. Clinically and pathologically, it needs to be differentiated from alveolar adenocarcinoma, adenosquamous carcinoma, pneumoblastoma, and metastatic endometrioid adenocarcinoma. The primary treatment for FACL is complete surgical excision and chemotherapy, with good outcome.