A case report of primary pulmonary meningioma masquerading as lung metastasis in a patient with rectal carcinoma: role of 18F-FDG PET/CT

Abstract

Background Primary pulmonary meningioma (PPM) is an extremely rare disease, which is often misdiagnosed as lung metastasis. Previous studies indicated that PPM usually showed homogeneous enhancement on enhanced CT and high uptake of 18F-fluorodeoxyglucose (18F-FDG) on positron emission tomography/CT (PET/CT). In this study, we report a case of PPM with atypical enhanced CT and 18F-FDG PET/CT features in a patient with rectal carcinoma. Case presentation A 70-year-old male was demonstrated to have rectal carcinoma by biopsy while a solitary pulmonary nodule (SPN) with well-defined edges measuring 13 × 13 × 15 mm was almost simultaneously found in the right lower robe on chest CT scan. Contrast-enhanced CT and PET/CT revealed mild centripetal enhancement of the nodule without accumulation of 18F-FDG. A thoracoscopic wedge resection of the right lower lobe was finally performed and histopathologic examinations and PET/CT imaging showed that the nodule was a PPM. Conclusion PPM is a rare disease with heterogeneity not only in blood supply but also in glucose metabolism. 18F-FDG PET/CT may be an effective method for differentiating benign and malignant SPNs. The diagnosis of PPM depends on pathological and radiological examinations.

Primary pulmonary meningioma and minute pulmonary meningothelial-like nodules: Rare pulmonary nodular lesions requiring more awareness in clinical practice

“…Malignant PPMs are prone to recurrence or metastasis, leading to a poor prognosis[ 3 , 16 , 17 ]. Conversely, some reports have indicated that the prognosis of patients with malignant PPM is actually favorable owing to a typically slow progression[ 6 ].…”

“…PET/CT has been proven to be more accurate than traditional CT in evaluating solitary pulmonary nodules. Low uptake of 18F-fluorodeoxyglucose (18F-FDG), defined as a maximum standardized uptake value (SUVmax) less than 1.5-2.0, is generally associated with a benign diagnosis[ 20 ], however, PPMs can present with various CT manifestations in enhanced imaging[ 6 , 7 , 21 ]. Therefore, the pattern of enhancement may not help determine whether the PPM is benign or malignant[ 7 , 22 , 23 ].…”

“…Overall, the imaging manifestations of PPMs are often heterogeneous between different patients. Although accurate diagnoses based on imaging results is of great significance for developing appropriate treatment plans, it is currently impossible to differentiate PPM from other pulmonary nodule diseases or to differentiate between benign and malignant PPM through radiographic observation alone[ 6 , 10 ]. Thus, pathological examination is the most accurate method of diagnosis of PPM[ 7 , 8 , 10 ].…”

“…In histopathological analyses, PPMs are typically categorized as epithelial, fibrous or transitional[ 13 ]. Further, they often exhibit spindle cells in whirlpool arrangements, while psammoma bodies can also be observed[ 5 , 6 , 8 , 13 , 15 , 19 ]. Pseudo-nuclear inclusions have also been reported in PPM histopathology[ 5 , 8 , 13 ].…”

“…Positive immunohistochemical staining for vimentin, epithelial cell membrane antigen, and progesterone receptor (PR) is common in most cases of PPM and MPMN[ 5 , 6 , 8 , 13 , 18 ], whereas markers such as S100, cytokeratin (CK), and CD34 may exhibit variable or inconsistent staining results[ 1 , 8 , 15 , 19 , 26 ]. The expression of thyroid transcription factor-1 and neuroendocrine markers, such as synaptophysin and chromogranin, are negative[ 6 , 31 ].…”