Using 18F-fluoro-2-deoxyglucose Positron Emission Tomography to DetectPrimary Lung Cancer in an Isolated Choroidal Metastasis

Ocular metastases, and particularly choroidal metastases, can precededetection of primary neoplasm, mainly lung cancers.¹ In39% to 51% of cases, primary tumors remain undetected despite intensive andinvasive investigations using conventional tools.¹ Basedon the increased glycolytic activity, positron emission tomography (PET) scanningis a new imaging method for locating cancer cells used in the localizationof primary tumors,² but it has never beenreported in ophthalmology. We report a case of choroidal metastasis from alung adenocarcinoma only diagnosed by PET scan.

A 50-year-old man was referred for choroidal metastasis of unknown origin.He had a 1-month history of blurred peripheral vision in the right eye andsevere loss of visual acuity. He had smoked 20 cigarettes per day for 35 years.Ophthalmic examination revealed visual acuity worse than 20/400 OD. Anteriorsegment examination of both eyes and fundus examination of the left eye hadnormal results. His right fundus showed a solid amelanotic lesion about 5disc diameters in the posterior pole, including the macula and the optic disc.It was associated with moderate inferior exudative retinal detachments. Ultrasonographicfindings of a largest tumor diameter of 14.5 mm and a height of 4 mm and highinternal reflectivity associated with fluorescein angiographic findings ofhyperfluorescence and numerous pinpoints (Figure 1) were consistent with the diagnosis of choroidal metastasis.Orbital computed tomography scan and magnetic resonance imaging (MRI) (Figure 2) showed a solid mass in the inferiortemporal quadrant of the right globe with contrast enhancement. Physical examinationresults were normal. Neither a primary tumor or additional metastases werefound despite extensive investigations including total-body computed tomography,neck ultrasonography, otorhinolaryngeal exploration, bronchoscopy, gastroscopyand colonoscopy, lumbar puncture, cerebral MRI, and bone scintigraphy. A whole-body18F-fluoro-2-deoxyglucose PET (FDG-PET) scan revealed 2 isolated hypermetabolicfoci in the left upper pulmonary lobe and the left hilum, while the eye lesionwas not detected (Figure 3 ). Thepatient received a short course of radiotherapy to the right eye. An upper-leftlung lobectomy was performed and confirmed a primary adenocarcinoma (2 cmdiameter; T1 N2 M1, stage IV). A chemotherapy of cisplatin and gemcitabinewas initiated. At 6 months' follow-up, the choroidal lesion was no longerpresent and visual acuity has stabilized.

Positron emission tomography scanning is able to identify a previouslyunknown occult primary tumor in 20% to 50% of patients after unsuccessfulconventional diagnostic investigations.² Nodata are available concerning the smallest size of a lesion that can be detected;detection depends on the lesion's metabolic activity. Furthermore, FDG-PETcontributes to detection of tumor dissemination, and to the patient's therapeuticmanagement.^3,4 The improvementof primary tumor detection rates is of great prognostic and therapeutic value,especially for patients with 1 solitary visceral metastasis, as an optionfor curative treatment is not unlikely.^3,4 Inour particular case, FDG-PET proved to be a very useful method for diagnosisand therapeutic management.

Correspondence: Dr Sève, Department of Internal Medicine,Hôtel Dieu, 1 place de l'Hôpital, 69288 Lyon Cedex 02, France(pascal.seve@chu-lyon.fr).