Mixed squamous cell and glandular papilloma of the lung resembling early adenocarcinoma: A case report

•Mixed squamous cell and glandular subtype is extremely rare pulmonary papilloma.•Initial presentation of this benign tumor had resembled early adenocarcinoma.•This disease should be taken into account in making a differential diagnosis.

IntroductionAn extremely rare case of mixed squamous cell and glandular papilloma of the lung is reported. The correlation between the radiological and the pathological features as well as the clinical pitfall in making a diagnosis is discussed.Presentation of caseAn asymptomatic 68-year-old female with a cigarette smoking habit presented with a small nodule in her peripheral lung. A wedge resection was performed though it failed on-site diagnosis which was instead obtained following pathological scrutiny. The postsurgical course was excellent with no recurrence of disease.DiscussionA small ground glass nodule gradually enlarged and transformed to a partially solid nodule a year and a half later. This transformation falsely made us suspect an early adenocarcinoma development. Eventually, the extremely rare subtype of pulmonary papilloma, with biphasic glandular and squamous cells, had been demonstrated to obstruct the peripheral bronchiole; and the adjoining alveoli had filled with a large volume of mucus. These pathological features seemed to have constituted the inner solid portion and the marginal ground glass portion respectively in the CT images, mimicking invasive lepidic adenocarcinoma.ConclusionBoth pre- and intra-operative diagnoses are difficult mainly because of the rareness of the disease, however, mixed squamous cell and glandular papilloma may be considered in case the presence of primary adenocarcinoma is not validated.