A Case of Solitary Pulmonary Papillary Adenoma

By Cunfu Fan¹, Junhong Cai²

Affiliations

1. Department of Pathology, Hainan Affiliated Hospital of Hainan Medical University, Hainan General Hospital, Haikou, Hainan Province, China
   
2. Medical Laboratory Centre, Hainan Affiliated Hospital of Hainan Medical University, Hainan General Hospital, Haikou, Hainan Province, China

doi: 10.29271/jcpsp.2025.08.1077

Sir,

A 57-year asymptomatic male patient, with a nodule in the lower lobe of the right lung identified during routine examination, was admitted to the hospital. On admission, chest CT revealed a small nodular shadow in the anterior basal segment of the lower lobe of the right lung, measuring 1.3 × 1.0 cm, with no calcification or cavity formation (Figure 1A). Wedge resection of the lower lobe of the right lung was performed via thoracoscopy. Postoperative pathological examination revealed the following: Lung wedge resection specimen size was 5.3 × 4.1 × 1.0 cm, mass size was 1.0 × 0.9 × 0.4 cm, and cut surface showed the mass to be greyish-white, medium in texture, solid, with no capsule, and clearly demarcated from the surrounding lung tissue. Light microscopy revealed the tumour composed of branching papillary structures with vascular-rich fibrous tissue in their cores (Figure 1B, C). The surface of the papillae was covered with a single layer of cuboidal to columnar epithelial cells, which were well-differentiated, lacked obvious heterogeneity, were uniform in size, had rounded and oval nuclei, clear nuclear membranes, inconspicuous nucleoli, fine chromatin, no nuclear fragmentation or necrosis, and did not invade the pleura. The immunohistochemical results were as follows: CK7 (+) (Figure 1D), Napsin A (+) (Figure 1E), TTF-1 (+) (Figure 1F), Ki-67 (+, approximately 2%) (Figure 1G), and P63 (-) (Figure 1H). The pathological diagnosis  was  pulmonary  papillary  adenoma.

Pulmonary papillary adenoma is a rare benign tumour of the lung. A literature search was performed, and 35 cases were reported in the English literature, 12 cases were reported in the Chinese literature,  and one case is reported in this paper.

Figure 1: (A) CT manifestations of pulmonary papillary adenoma. (B) Papillary architecture of pulmonary papillary adenoma (HE, ×40). (C) Cells covering the papillary structures (HE, ×400). (D) Tumour cells with positive expression of CK (EnVision, ×200). (E) Tumour cells positive for Napsin A expression (EnVision, ×200). (F) Tumour cells positive for TTF-1 expression (EnVision, ×200), (G) Tumour cells with a low proliferation index for Ki-67 (EnVision, ×200). (H) Tumour cells negative for P63 expression (EnVision, ×200).

The pathogenesis of pulmonary papillary adenoma has not yet been clearly determined.¹ Pulmonary papillary adenoma patients usually have no special clinical symptoms, and it is usually detected by the x-ray and CT examinations during routine examinations. These tumours are mostly observed in males, and the age of onset ranges from 2 months to 75 years (mean age: 34 years).² This patient was a male and asymptomatic, which is in line with the literature. Tumours are usually isolated nodules, mostly located in the parenchyma of the peripheral part of the lung, but a few are located centrally. Although pulmonary papillary adenoma is a benign tumour, it has the potential for metastasis.³ Liu et al. reported a case of papillary adenoma in the middle lobe of the right lung with left lung metastasis.⁴ Lobectomy or segmental resection is preferred for the treatment of this tumour.⁵ Papillary adenoma needs to be differentiated from sclerosing pneumocytoma, papillary adenocarcinoma, alveolar adenoma, and adenomatous papilloma. Pulmonary papillary adenoma is a benign tumour with few recurrences after treatment and a relatively good prognosis, but it is prone to misdiagnosis on intra- operative frozen sections and routine pathological diagnosis; thus, pulmonary papillary adenoma should be diagnosed on the basis of pathomorphological and immunohistochemical markers combined with tumour imaging features. Owing to the small number of reported cases of pulmonary papillary adenoma, there is a lack of understanding of the incidence of malignancy and risk factors; therefore, further in-depth study is  needed.

COMPETING   INTEREST:
The  authors  declared  no  conflict  of  interest.

AUTHORS'  CONTRIBUTION:
CF, JC: Substantial contribution to the conception, design of the work, acquisition, analysis, interpretation of the data, drafting of the work, and revision of the manuscript for important intellectual content.
Both authors approved the final version of the manuscript to be published.

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