[Atypical adenomatous hyperplasia of lung: clinicopathologic study of 8 cases and review of literature].

Objective: To study the clinicopathologic and immunohistochemical features of atypical adenomatous hyperplasia (AAH) of lung.

Methods: Eight cases of AAH of lung were studied by light microscopy and immunohistochemical staining for p16, thyroid transcription factor-1 (TTF-1), Ki-67, p53, epidermal growth factor receptor (EGFR) and c-erbB-2.

Results: The mean age of the patients was 52 years. The male-to-female ratio was 1:3. Two patients were chronic smokers. The clinical symptoms were relatively non-specific. Three patients had past history of non-pulmonary tumors, while 4 patients had lung adenocarcinoma. CT scan revealed solitary or multifocal hyperdense opacities. Histologically, the lesions ranged from 1 mm to 6 mm in size. Two cases were solitary and 6 cases were multifocal. All were of high-grade lesions. Associated low-grade component was noted in 3 cases. There was no evidence of local recurrence or disease progression in the 7 patients with post-operative follow-up information available (mean duration of follow up = 23 months). Four patients had received chemotherapy as well. Immunohistochemical study showed variable positivity for p16 (5/8), TTF-1 (5/8), Ki-67 (with proliferation index ranging from 1% to 10%), p53 (1/8) and EGFR (1/8). The staining for c-erbB-2 was negative (0/8). Four cases of AAH were associated with pulmonary adenocarcinoma. The adenocarcinoma cells were diffusely positive for TTF-1 (4/4), variably positive for p16 (2/4), Ki-67 (with proliferation index ranging from 2% to 40%), p53 (1/4) and EGFR (3/4), and negative for c-erbB-2 (0/4).

Conclusions: AAH of lung is associated with pulmonary adenocarcinoma. Diagnosis of AAH requires correlation with CT findings and pathologic examination.