¹⁸F-Labeled Fluoro-2-Deoxyglucose Positron Emission Tomography and Computed Tomography in a Large Pulmonary Sclerosing Pneumocytoma with Contralateral Lung Metastasis

A 22-year-old woman presented with dull aching chest pain on the right side for 3 years and dry cough for 6-month duration. Initial chest radiographs posteroanterior view showed a rounded homogenous opacity occupying the right middle and lower zone and a smaller rounded homogeneous opacity on the left side [Figure 1a, white arrows]. She was lost to follow-up and presented a year later with the same complaints. A repeat chest radiograph was obtained, which showed the masses to be of similar extent [Figure 1b, white arrows]. Ultrasound-guided biopsy of the mass done initially was suggestive of adenocarcinoma. Hence, to evaluate the disease extent, ¹⁸F-labeled fluoro-2-deoxyglucose positron emission tomography and computed tomography (¹⁸F-FDG PET/CT) were performed. The maximum intensity projection image showed an area of inhomogeneous FDG uptake in the right hemithorax and a faint focal FDG uptake in the left hemithorax [Figure 1c, black arrows]. The transaxial and coronal CT and fused PET/CT images showed a large FDG avid well-defined heterogeneously enhancing mass measuring approximately 14.0 cm × 12.4 cm (SUVmax - 7.1) involving all three lobes of the right lung [Figure 1d and e; white arrows]. A small similar morphology lesion measuring approximately 2.0 cm × 2.0 cm (SUVmax - 2.1) was noted in the lower lobe of left lung [Figure 1f and g; white arrows]. The histopathology slides were reviewed on the ¹⁸F-FDG PET/CT findings. Hematoxylin and eosin-stained slides [Figure 1h; ×100, low-power image] showed nodular aggregates of poorly cohesive cells. High-power image [Figure 1i; ×400, high-power image] showed cuboidal to columnar atypical cells displaying small round vesicular nuclei, inconspicuous nucleoli and moderate amount of pale eosinophilic cytoplasm. Immunohistochemistry of the tumor was positive for TTF-1 and negative for p40 and synaptophysin. The patient then underwent surgical removal of the tumors on either side and is now on follow-up.

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Figure 1 Panels (a-b) are chest radiographs of the patient showing the opacities in the bilateral lung fields. Panel (c) shows the whole body 18F-FDG PET/ CT maximum intensity projection inhomogeneous FDG uptake in the right hemithorax and a faint focal FDG uptake in the left hemithorax. Panels (d-g) shows the computed tomography and fused PET/CT images showing the lung masses. Panels (h-i) shows the low power and high-power hematoxylin and eosin-stained slides showing cuboidal to columnar atypical cells displaying small round vesicular nuclei, inconspicuous nucleoli and moderate amount of pale eosinophilic cytoplasm.

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Pulmonary sclerosing pneumocytoma (PSP), previously known as pulmonary sclerosing hemangioma, is an exceedingly rare neoplasm of the lung, first described by Leibow and Hubbell in 1956.[1] The tumor consists of a dual population of immature Clara cells (Type II pneumocytes) and embryonic respiratory epithelium (round cells). These are usually slow growing with a benign disease course but can easily be mistaken for carcinoid tumors or adenocarcinoma in cytology or histopathology specimens,[2] as was with our case initially. Few studies have reported rare incidences of metastasis to mediastinal lymph nodes[34] and stomach.[5] ¹⁸F-FDG PET/CT has been used in the evaluation of these tumors with different studies depicting a highly variable ¹⁸F-FDG uptake.[6789] To the best of our knowledge, this is the largest PSP reported till now in the literature. PSP is a benign slow-growing tumor, but rare occurrences of metastases warrant long-term follow-up. ¹⁸F-FDG PET/CT is useful in the detection of rare occurrences of metastases in cases of PSP thereby giving a guidance to management.