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Editor,—Juvenile xanthogranuloma (JXG) is a rare disorder of infants and very young children affecting the ocular structures, particularly the iris.
It is characterised by spontaneous hyphaema associated with a yellowish, poorly demarcated iris tumour and increased intraocular pressure; the aetiology is unknown.1 The ocular lesions are usually unilateral and should be differentiated from amelanotic melanoma, iris leiomyoma, haemangioma, and other iris lesions.2-4 Early diagnosis and treatment determine the final visual outcome.
The aim of the present study was to describe the use of ultrasound biomicroscopy (UBM) to define precisely the location of the tumour before excision and to correlate the UBM findings with the histopathological pattern.
A 2 year old girl was evaluated for an iris lesion. Past medical history showed two events of febrile convulsions at 1 year of age. Computed tomography of the brain, electroencephalography, and lumbar puncture were normal. Fixation and follow up movement were normal in both eyes. Ophthalmological examination revealed an unusual yellowish brown stromal lesion with an irregular surface in the nasal side of the left iris (Fig 1). It occupied the whole iris, from the angle to the pupillary border. Abnormal vascularisation and a small hyphaema were also noted. Except for the iris lesion, the anterior and posterior segments were completely normal. The examination of the right eye was unremarkable. Systemic evaluation revealed normal findings. On examination under anaesthesia, Tonopen tonometry revealed a pressure of 23 mm Hg, and microscopy showed a 3.4 mm × 4 mm mass located in the lower nasal quadrant between the 7 o’clock and 11 o’clock positions, with pupillary distortion. UBM was subsequently performed and a full thickness, solid stromal lesion of the iris was observed, with a homogeneous internal reflectivity and slightly irregular surface with no surface plaque. There was no involvement beyond the iris root. Lesion thickness measured 1.2 mm (Fig 2).
Sector iridectomy was performed in order to remove the whole lesion together with clinically normal looking temporal and nasal margins.
Viscoelastic material was used to prolapse the involved iris segment out of the eye through a wide limbal incision, and the iris was excised at the root. Histopathological evaluation revealed a cellular mass occupying the entire iris stroma and consisting of numerous histiocytes, some of them containing clear cytoplasmic vacuoles. Among these cells a few lymphocytes, plasma cells, and iris melanocytes were noted. Immunohistochemical staining for CD-68, a histiocytic marker, was positive in the majority of the histiocytic cells. Immunohistochemical staining for HMB-45, a melanoma cell marker, was negative. Touton giant cells were noted among the histiocytic cells (Fig 3). According to these histopathological findings a diagnosis of juvenile xanthogranuloma was made.
The present study shows the importance of preoperative UBM evaluation in identifying the nature and location of any iris lesion in childhood, before surgical excision is performed.
The homogeneous cellularity of the whole mass together with the absence of significant vascular channels on histology correlated with the homogeneous reflectivity on the UBM. The slightly irregular surface of the tumour and lack of vascular channels helps to differentiate JXG from iris melanoma, which generally show more variable internal reflectivity patterns including a linear more highly reflective pattern in the superficial layer and lobulated appearance with internal space representing blood vessels.5
In our case, UBM was the major technique which allowed us to determine the characteristics, thickness, location, and possible spread of the lesion. By defining the precise boundaries of the lesion and ruling out involvement of the iridocorneal angle or ciliary body, UBM was found to be very helpful in planning the complete surgical excision of this iris tumour.