Positive FDG-PET/CT of the Pleura Twenty Years after Talc Pleurodesis: Three Cases of Benign Talcoma

Abstract

The FDG-PET (fluorine-18 fluorodeoxyglucose positron emission tomography) scan is used with increasing frequency to investigate pleural abnormalities and to determine the possibility of neoplastic invasion. However, false-positive findings are not uncommon and talc pleurodesis has been reported to cause hypermetabolic pleural thickenings up to 5 years after the procedure. We report the cases of 3 patients (2 of whom had a history of asbestos exposure) requiring talc pleurodesis for recurrent pneumothoraces between 1988 and 1990, who were investigated in 2011 for pleural abnormalities. Avid pleural thickening on FDG-PET scan mimicking pleural cancer was found, but this was deemed secondary to the pleurodesis. Talc pleurodesis generates inflammation which promotes pleural adhesions. This inflammatory reaction could decrease with time, as in other inflammatory processes. Since talc is not metabolized by the body, the FDG-PET scan can remain positive, most likely because of a foreign-body granulomatous reaction, even 20 years later. It is important to be aware of this possibility and to question patients with pleural abnormalities about past procedures and mention such procedures to the colleagues who are responsible for interpreting metabolic imaging. Follow-up of hypermetabolic pleural lesions attributed to talc pleurodesis is important for the detection of new pleural lesions or neoplastic evolution.

Pleural talcomas present pitfalls in workup of pleural masses

“…Since the first case report of pleural FDG uptake posttalc pleurodesis was published 4 there have been several more cases published in literature. 2,3 As was the case in our patient, in the vast majority of cases, the pleural changes associated with talc pleurodesis are asymptomatic and are often discovered incidentally. 3,4 They are most readily seen on CT scans as pleural thickenings or nodularities with or without calcification and are usually localised to the posterior, caudal portions of the pleura.…”

“…2 Although, highly effective, talc has been shown to cause hypermetabolic pleural thickenings for more than 20 years after the initial procedure. 3 These thickenings may sometimes present as incidental pleural masses, talcomas that may be interpreted incorrectly as malignancies. 3 We present a patient with a slowly growing, FDG-avid, lobulated right pleural mass presenting several years after her talc pleurodesis.…”

“…3 These thickenings may sometimes present as incidental pleural masses, talcomas that may be interpreted incorrectly as malignancies. 3 We present a patient with a slowly growing, FDG-avid, lobulated right pleural mass presenting several years after her talc pleurodesis.…”

Diagnosis and Treatment of Malignant Pleural Mesothelioma

“…13 However, its sensitivity and specificity for detecting N2 disease in mesothelioma is low, 14 and false negatives may be found in tuberculous pleurisy, 15 empyema 16 or in patients with a history of previous pleurodesis. 17 Magnetic resonance imaging (MRI) provides greater contrast than CT for defining tumor chest wall invasion, but it cannot reliably detect metastatic disease. 18 …”

Diagnóstico y tratamiento del mesotelioma pleural maligno

“…La PET-TC desempeña un papel relevante en la estadificación preoperatoria del mesotelioma pleural maligno, en la valoración de la respuesta al tratamiento y para detectar la posible aparición de recidivas 13 . No obstante, su sensibilidad y especificidad son bajas para detectar enfermedad N2 en el mesotelioma 14 , y pueden observarse falsos positivos en pleuritis tuberculosa 15 , empiema 16 o en pacientes con historia de pleurodesis previa 17 .…”