Incidental detection of a tumour on 68-Gallium DOTANOC PET/CT.

CASE REPORT

A 60-year-old gentleman with known diagnosis of ileocecal neuroendocrine tumor (NET) underwent right hemicolectomy with ileocecal anastomosis. On 68-Gallium DOTANOC-PET/CT scan, multiple somatostatin receptor positive hepatic lesions were detected. Incidentally, a well defined fat density lesion was found in the left lung.

Figure 1 shows axial CT and fused PET/CT images showing a left intrathoracic fat density lesion [Figure 1a] with no 68-gallium DOTANOC uptake in it [Figure 1b]. In lung window settings, no extension in to adjacent lung parenchyma is noted [Figure 1c] with no 68-gallium DOTANOC uptake in it [Figure 1d].

Figure 1

(a) Axial contrast-enhanced CT in soft tissue window shows a well defined left pleural lesion with fat density, which on fused 68-Gallium DOTANOC PET/CT (b) shows no somatostatin receptor expression. (c) In lung window axial CT, there is a lesion seen in the left thoracic cavity, with no extension into the adjacent lung parenchyma. (d) Fused 68-Gallium DOTANOC PET/CT in the lung window shows no somatostatin receptor expression in this lesion

QUESTION

Q1: What is the diagnosis?

ANSWER

Pleural lipoma.

Intrathoracic lipomas are classified depending upon the location as endobronchial, parenchymal, pleural, and mediastinal. Pleural lipomas arise from submesothelial parietal pleura and may extend into subpleural, pleural, and extrapleural spaces.[1]

The incidence of pleural lipoma is low. The first case of pleural lipoma was described in 1783 by Fothergill.[2] The largest series is of six patients found among 4000 CT chest evaluations.[3] In another series by Jenson et al., there were only 3 (0.08%) cases of intrathoracic lipoma found in a review of 3502 cases of thoracic tumors.[4]

Pleural lipomas are seen as space-occupying lesions on chest X-ray. CT chest is confirmatory which shows presence of homogenous fat density (Hounsfield units: Negative usually up to −150). The density may not be entirely uniform and there may be presence of fibrous stroma.[5]

Treatment is required if patients are symptomatic, and consists of surgical removal.