Background: Atypical adenomatous hyperplasia (AAH) is a possible precursor lesion of adenocarcinoma of the lung, but very few reports of AAH have focused on the autopsy lung.
Methods: We intended to clarify the characteristics of AAH in the general population by using 207 autopsy cases, ranging in age from 0 to 90 years old.
Results: A total of 179 eligible cases (86.5%) and 1265 tissue slides (7.0 per case) was examined independently by two pathologists. One hundred seventy-nine autopsy cases consisted of 125 males and 54 females, whose median ages were 38 (range 0-90) and 31 (range 0-81) years old, respectively. AAH was microscopically found in five of 179 autopsy cases (2.8%). The male/female ratio was 5/0 and age distribution was 52-63 years of age (median 57). One of five cases with AAH harbored esophageal carcinoma, but the others had no present or previous malignant neoplasm. One of five lesions was high grade and the others were low grade. All five cases showed positive immunoreactivity for proSP-C, a type II pneumocytes marker, but not for p53, Ki-67 or CEA.
Conclusions: The incidence of AAH was very low in the general autopsy cases, as compared with the previously reported surgically resected lung and senile autopsy cases, and AAH seems to occur after middle age in general.