Case SP14-12

​History

A 51-year-old woman presented to the emergency department for left-sided chest pain that worsened with breath, touch, cough, and movement. Chest x-ray and computed tomographic scan showed an incidental 2.8 × 2.4–cm, solid nodule in the right upper mediastinum juxtaposed to the superior vena cava, azygous vein, and phrenic nerve (Image 1). Positron-emission tomographic scan showed mildly elevated fluorodeoxyglucose uptake with a maximum standardized uptake value of 3.3. The remainder of the workup, including an electrocardiogram, was negative for any acute cardiac events. After thorough medical evaluation, the nodule was resected.

Video-assisted thoracoscopic surgery was performed to evaluate and resect the mediastinal nodule. No nodule was found within the mediastinum, and the procedure was converted to a right posterolateral thoracotomy. The nodule was subsequently found to be subpleural, within the right upper lobe of the lung. Wedge resection was performed and the specimen was delivered to the pathology laboratory for frozen-section analysis.

Grossly, the nodule was 3.0×2.6×2.4 cm, well circumscribed, and tan, with punctate yellow areas, 1 hemorrhagic area, and 1 small cyst (Image 2). A second, 0.2-cm diameter, nodule was identified in a second wedge resection. Neither tumor involved the visceral pleura. Margins were negative by 0.6 and 0.3 cm, respectively.

Microscopically, the largest nodule was well circumscribed, sharply demarcated from the surrounding benign lung parenchyma, and characterized by solid, sclerotic, and papillary areas with a biphasic cell population (Image 3). The solid areas were predominant and were composed of round cells with eosinophilic cytoplasm and well-defined cytoplasmic borders (Image 4). The nuclear chromatin was fine and nucleoli were not apparent. Sclerotic foci were present within these solid areas. Focal papillary architecture was also present with sclerotic fibrovascular cores lined by surface cuboidal cells with abundant eosinophilic cytoplasm and mild nuclear atypia. Similar surface cuboidal cells were also identified forming glandular structures scattered throughout the areas of solid architecture. Rare intranuclear inclusions were identified (Image 5). Mitoses were 3 not identified. The second small nodule had similar gross and histologic features. The frozen-section diagnosis was primary sclerosing hemangioma (pneumocytoma).

Confirmatory immunohistochemical stains were performed (Image 6, A-D). All cells showed positive staining for TTF-1 and EMA (Images 6B and 6C). The surface cuboidal cells were positive for pancytokeratin AE1/3; the round cells were negative for pancytokeratin AE1/3 (Image 6D).

The gross appearance, microscopic appearance, and immunohistochemical profile were characteristic of pulmonary sclerosing hemangioma (pneumocytoma).

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