ABSTRACT
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.
Subject(s)
Adenomatosis, Pulmonary/pathology , Lung Neoplasms/pathology , Adenocarcinoma/chemistry , Adenocarcinoma/pathology , Adenomatosis, Pulmonary/chemistry , Adolescent , Adult , Aged , Aged, 80 and over , Autopsy , Biomarkers, Tumor/analysis , Child , Child, Preschool , Female , Humans , Hyperplasia/pathology , Infant , Infant, Newborn , Lung Neoplasms/chemistry , Male , Middle Aged , Prevalence , Retrospective StudiesABSTRACT
An increasingly large body of work suggests that atypical adenomatous hyperplasia (AAH) of the lung may be a forerunner of pulmonary adenocarcinoma. Recognizing this fact, the World Health Organization now acknowledges the existence of AAH while noting difficulties that may be encountered in distinguishing AAH from the nonmucinous variant of bronchioloalveolar carcinoma. Regrettably, a universally acceptable definition of morphologic criteria for the diagnosis of AAH has not been achieved. This review of the literature examines the epidemiology, gross appearance, light microscopic findings, morphometry, immunohistochemistry, and molecular features of AAH and suggests a set of histopathologic features that may help the practicing pathologist identify this intriguing lesion. These features include the following: irregularly bordered focal proliferations of atypical cells spreading along the preexisting alveolar framework; prominent cuboidal to low columnar alveolar epithelial cells with variable degree of atypia but less than that seen in adenocarcinoma; increased cell size and nuclear-cytoplasmic ratio with hyperchromasia and prominent nucleoli, generally intact intercellular attachment of atypical cells with occasional empty-looking spaces between them without high cellularity and without tufting or papillary structures; and slight thickening of the alveolar walls on which the AAH cells have spread, with some fibrosis but without scar formation or significant chronic inflammation of the surrounding lung tissue. Several lines of evidence indicate that AAH is a lesion closely associated with adenocarcinoma of the lung, suggesting AAH may be involved in the early stage of a complex multistep carcinogenesis of pulmonary adenocarcinoma.
