Journal of Toxicologic Pathology
Online ISSN : 1881-915X
Print ISSN : 0914-9198
ISSN-L : 0914-9198
Case Report
Smooth muscle hamartoma of the lungs in a Wistar Hannover rat
Shinya MiyazakiChinatsu FujiwaraYoshitaka KatohTsuyoshi ItoAya KoyamaNaofumi TakahashiAtsushi ShigaTakanori Harada
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JOURNAL OPEN ACCESS

2023 Volume 36 Issue 4 Pages 193-198

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Abstract

Hamartomas are tumor-like masses comprising disorganized normal tissue elements. To date, spontaneous hamartomas have been reported in several organs and tissues in rodents but not in the lungs. Here, we report the first case of a hamartoma in the lungs of a 108-week-old female Wistar Hannover rat. Grossly, a white spot, 7 mm in diameter, was observed on the costal surface of the left lung. Histopathologically, the nodular lesions adjacent to the bronchioles comprised mature smooth muscle cells. The lesion was not encapsulated and spread along the alveolar walls and ducts without compression of the surrounding tissue. In the nodules, elastic fibers enclosed small lumens lined with factor VIII-related antigen-positive endothelial cells. This structure suggested that the nodule mimicked an artery. Moreover, structural abnormalities were observed within the bronchioles and arterioles owing to the increased number of smooth muscle cells in the surrounding tissues. These features suggested that this was a case of tissue malformation rather than a neoplasm, leading to the diagnosis of a smooth muscle hamartoma of the lung.

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© 2023 The Japanese Society of Toxicologic Pathology
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