Incidental pleural lipoma in a case of calculous cholecystitis

Clinical History

A 54-year-old male patient presented with the chief complaints of abdominal pain with dark urine for 3-4 days. The patient was a non-smoker and non-alcoholic. He gave no other significant history.

Imaging Findings

Ultrasound of abdomen (Fig. 1) revealed multiple calculi averaging approximately 5 to 6 mm. Routine PA Chest Radiograph (Fig. 2) showed a radio-opaque lesion in the right midzone with well-defined margins superiorly, medially and inferiorly, while the lateral margin was obscured by the chest wall. The lesion showed obtuse angles with the chest wall suggesting its pleural-based origin. Chest CT (Fig. 3, 4) plain and post-contrast showed that the lesion was non-enhancing with fat attenuation of approx. -109 Hounsfield Units. The lesion measured approx. 4.7 by 3 cm.

Discussion

Pleural lipomas are extremely rare benign tumours that originate from the submesothelial layers of the parietal pleural and extend into the subpleural or extrapleural space. They show a slow pattern of growth. These lesions are mostly solitary and involve both sides with equal frequencies. Rarely these lesions may cause symptoms secondary to mass effect such as cough, chest pain, dyspnoea, heaviness of the chest or even back pain. [1, 2] On chest radiograph, they appear as smooth, rounded nodules/masses. CT is the imaging modality of choice. Radiological diagnostic criteria for pleural lipomas include a well-defined mass with homogeneous fat density (-50 to -150 HU), which does not enhance on contrast administration, forms obtuse angles with the chest wall and displaces adjacent pulmonary parenchyma and vessels. [2-4] Advantages of CT include differentiating between pleural and parenchymal disease, determining the location and extent of the lesion as well as characterization of the tissue based on its attenuation. Ultrasound may help in confirming the pleural origin of the tumour, including providing information whether the lesion is cystic or solid and confirming its fat density and homogeneity. MRI is done only if there is a doubt in radiological diagnosis by CT. It gives a better delineation of the relationship between the tumour and the chest wall. MRI can also differentiate between diaphragmatic hernias and eventrations from lipomas arising near the diaphragm. However, the main role of MRI is its value in differentiating lipomas from liposarcomas.[2, 4] Management of pleural lipomas is not clearly established and is controversial. In the elderly, and especially in those patients with small and asymptomatic lesions, clinical and imaging follow-up is suggested. However, certain authors suggest surgical radical excision as the treatment of choice. The three main reasons for this are: it allows diagnosis by histopathology especially in non-homogenous lesions, allows relief of symptoms and lastly it limits the mass effect on adjacent organs. [3-5] Surgical options include open typical or muscle-sparing thoracotomy, video-assisted thoracoscopic surgery (VATS), and extirpation of pleural lipomas by a single port VATS. [2, 3] Complications, although rare, include compression of adjacent organs, rib lysis secondary to invasion of intercostal spaces and intratumoural haemorrhage causing pain and fever. There is no known secondary transformation of pleural lipomas to liposarcomas. [4, 5] Features favouring liposarcoma include large lesion size, thick septa, nodular and/or globular or non-adipose mass-like areas, decreased percentage of fat and advanced patient age. [6]

Differential Diagnosis List

Final Diagnosis

Incidental pleural lipoma in a case of calculous cholecystitis

URL:	https://www.eurorad.org/case/12770
DOI:	10.1594/EURORAD/CASE.12770
ISSN:	1563-4086