# Alveolar adenoma with a single cyst: A case report

## TL;DR

A 50-year-old man with a rare benign lung tumor called alveolar adenoma was diagnosed after a 3-year follow-up and surgery confirmed the condition.

## Contribution

This case report adds to the limited clinical knowledge of alveolar adenoma by presenting a confirmed diagnosis and long-term follow-up.

## Key findings

- Alveolar adenoma was confirmed via histopathological and immunohistochemical analyses after thoracoscopic wedge resection.
- The patient showed no malignancy and had no recurrence after 46 months of follow-up.
- Pre-operative diagnosis of alveolar adenoma is challenging due to its similarity to other lung tumors.

## Abstract

Alveolar adenoma is a rare and benign pulmonary tumor, which originates from type II pneumocytes and is often incidentally identified on radiographic images. Alveolar adenoma presents as a peripleural, solitary and cystic nodule in the lung and may mimic other types of lung tumors, thus rendering its differential diagnosis difficult. Alveolar adenoma is diagnosed based on histopathological and immunohistochemical analyses. The present study describes the case of a 50-year-old male patient with alveolar adenoma. He visited a local doctor ~3 years prior due to left chest pain. A chest computed tomography scan revealed a cystic lesion in segment 8 of the left lung. A nodular shadow appeared in the cyst and gradually increased in size; the patient was thus referred to the authors' hospital. The nodule was well-defined, solitary and solid; thus, lung cancer or aspergilloma were suspected. Thoracoscopic wedge resection was performed as diagnostic therapy. The frozen sections were non-diagnostic, and a pathological examination revealed an alveolar adenoma with no evidence of malignancy and a negative culture. The patient had a good post-operative course, with no sign of recurrence at the follow-up evaluation 46 months later. On the whole, alveolar adenoma is a rare, benign pulmonary tumor that is difficult to diagnose pre-operatively.