Myofibrosarcoma infiltrating pulmonary arteries diagnosed on 18F-FDG PET/CT

Abstract

This image demonstrated a 59-year-old male patient presenting with severe cough and pulmonary artery involvement by lung nodule. The patient was urgently admitted for hospitalization and underwent 18F-fluorodeoxyglucose positron emission tomography/CT (18F-FDG PET/CT) examination on a total-body PET/CT scanner (United Imaging Healthcare) with an injection dose of 8.2 mCi. Maximum intensity projection image showed an irregular nodule at the superior lobe of the left lung with increased metabolism (Fig. 1a, red arrow), accompanied by 18F-FDG uptake at multiple lymph nodes (blue arrowheads). The nodule has heterogenous glucose metabolism (SUVmax = 4.1–5.9, Fig. 1b–d) and infiltrated bilateral pulmonary arteries (red arrow, Fig. 1e), forming emboli that may lead to pulmonary and brain embolism. Disseminated pulmonary nodules with varying uptake (SUVmax = 2.6–3.1, white arrows) were also found (Fig. 1f, g). The patient underwent mediastinoscopy biopsy, and histopathological staining showed proliferation of spindle cells with round-oval nuclei and scant eosinophilic cytoplasm. The spindle cells are arranged in short fascicles and interspersed by hyalinized collagen (Fig. 1h). Immunohistochemistry showed positive staining of vimentin, betacatenin (membrane), BAP1, and smooth muscle actin (Fig. i). Negative stainings were found for CD34 (Fig. 1j), panCK (Fig. 1k), H-caldesmon (Fig. 1l), STAT6 (Fig. 1m), and desmin. Based on the above evidence and literature report [1], lung myofibrosarcoma was diagnosed. The patient has achieved a partial response after two cycles of treatment consisting of multi-kinase inhibitor anlotinib and PD-1 inhibitor sintilimab. Although myofibroblastoma has low 18F-FDG uptake [2, 3], myofibrosarcoma may present with intrathoracic lesions with heterogeneous 18F-FDG uptake.