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Knapp–Rønne choroidal melanoma: a clinicopathological report

      A 37-year-old white male was evaluated for a melanotic fundus lesion with vitreous floaters diagnosed a month prior. Visual acuity was 20/25 in both eyes, with bilateral normal intraocular pressure and anterior segment examination. Funduscopy of the left eye revealed a preretinal spherical dark brown tumour with a smooth surface with minimal subretinal base visible at its superior border (Fig. 1A). Despite its dark colour, prominent vessels could be detected clinically beneath the tumour surface. The retina appeared eroded by invasion of the tumour from choroid into the vitreous. The superior branch of the superotemporal retinal vein appeared to be encased within the tumour mass. Patches of pigment were scattered on the retinal surface along the inferotemporal arcade (Fig. 1B). Few pigmented cells were floating within vitreous. Ultrasonography demonstrated a round lesion of 5.6mm thickness, with medium internal reflectivity, and choroidal excavation (Fig. 1C). Fluorescein angiography showed complete blockage of choroidal fluorescence by the dark lesion throughout the angiogram; nevertheless, there was late fluorescein leakage from prominent wormlike engorged vessel at tumour apex (Fig. 1D). Because of its unusual presentation, with dark coloration and dispersion of pigmented cells, the differential diagnosis included choroidal melanoma, melanocytoma, and pigment epithelial neoplasm. Tumour biopsy was performed that was complicated by massive intraoperative haemorrhage from the tumour. Cytopathology revealed malignant melanoma cells. Because of extensive intraocular dispersion of tumour cells in association with extensive vitreous haemorrhage, enucleation was undertaken.
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      Fig. 1A, Funduscopy of a heavily pigmented lesion obscuring the retinal vasculature. B, Dispersion of pigmented cells on retinal surface along the inferotemporal arcade. C, Ultrasonography shows a round-shaped lesion of 5.6mm thickness. D, Fluorescein angiography shows fluorescein leakage from engorged vessels at the tumourapex.
      Histopathology showed a choroidal melanoma of mixed-cell type (Fig. 2A), intensively stained with HMB-45 (Fig. 2B). The tumour showed dilated vessels near the apex with few vascular spaces without endothelial lining (Fig. 2C). The sensory retina covered tumour periphery (Fig. 2D), but centrally, the retina was totally replaced by the tumour, which invaded into the vitreous. The clinical and pathologic findings suggested a choroidal melanoma of Knapp–Rønnetype.
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      Fig. 2A, Low-power photomicrograph of a narrow-based, round, choroidal melanoma (hematoxylin and eosin [H&E], original magnification×12.5). B, Intense and diffuse immunostaining for HMB-45 confirming the melanocytic origin of the tumour. The boundary between the invasive tumour and the replaced neurosensory retina is discernible near tumour apex to the right (brown chromogen, original magnification×40). C, Apex of the tumour showing dense pigmentation, dilated vessels, and vascular lakes (horizontal arrow); the tumour is in direct contact with the vitreous (vertical arrow; H&E, original magnification×200). D, Photomicrograph nearer to tumour base showing, from right to left, progressive thinning of the retina from the base toward tumour apex, with subretinal bleeding (H&E, original magnification×200).
      This type of melanoma is named after Herman Knapp
      • Knapp H.
      Vierzehnter Fall. Weisses, vaskulares (telangiektatisches) Sarkom der Aderhaut. Heilung durch Enucleatio bulbi, in Die intraocularen Geschwulste.
      and Henning Rønne,
      • Ronne H.
      Preretinal choroidal melanosarcoma.
      who first described this rare growth pattern that manifests in 0.4% of choroidal melanomas. Knapp–Rønne melanoma is characterized by its location near the papilla, its early penetration of the sensory retina with invasion into vitreous, its histology with bloodless and blood-filled cavernous spaces, and its frequent manifestation by massive vitreous hemorrhage.
      • Knapp H.
      Vierzehnter Fall. Weisses, vaskulares (telangiektatisches) Sarkom der Aderhaut. Heilung durch Enucleatio bulbi, in Die intraocularen Geschwulste.
      • Ronne H.
      Preretinal choroidal melanosarcoma.
      • Jensen O.A.
      The “Knapp-Ronne” type of malignant melanoma of the choroid. A haemangioma-like melanoma with a typical clinical picture. So-called “preretinal malignant choroidal melanoma.”.
      • Laqua H.
      • Volcker H.E.
      Pars plana vitrectomy in eyes with malignant melanoma.

      Pülhorn G, Winter R. Malignes Melanom der Uvea vom Typ “Knapp-Ronne”. Klin Monatsbl Augenheilkd 1976;169(3):352–8

      Knapp–Rønne melanoma also has been termed as vitreous melanoma, haemangioma-like malignant melanoma, and preretinal choroidal melanosarcoma.
      • Knapp H.
      Vierzehnter Fall. Weisses, vaskulares (telangiektatisches) Sarkom der Aderhaut. Heilung durch Enucleatio bulbi, in Die intraocularen Geschwulste.
      • Ronne H.
      Preretinal choroidal melanosarcoma.
      • Jensen O.A.
      The “Knapp-Ronne” type of malignant melanoma of the choroid. A haemangioma-like melanoma with a typical clinical picture. So-called “preretinal malignant choroidal melanoma.”.
      This growth pattern differs from retinal invasion of a collar button melanoma, in which a portion of the tumour grows between Bruch’s membrane and sensory retina before retinal invasion. No particular histologic features have been observed to explain the Knapp–Rønne melanoma growth behaviour. Tumour-related hemorrhage is a presenting manifestation in 3% of melanomas generally.
      • Laqua H.
      • Volcker H.E.
      Pars plana vitrectomy in eyes with malignant melanoma.
      It was postulated that the greater propensity to hemorrhage in Knapp–Rønne melanoma is due to marked engorgement of tumour feeding vessels by the strangulating effect of Bruch membrane.
      • Jensen O.A.
      The “Knapp-Ronne” type of malignant melanoma of the choroid. A haemangioma-like melanoma with a typical clinical picture. So-called “preretinal malignant choroidal melanoma.”.
      • Laqua H.
      • Volcker H.E.
      Pars plana vitrectomy in eyes with malignant melanoma.

      Pülhorn G, Winter R. Malignes Melanom der Uvea vom Typ “Knapp-Ronne”. Klin Monatsbl Augenheilkd 1976;169(3):352–8

      This entity is to be recognized by its clinical features to be differentiated from other heavily pigmented fundus tumours with dispersion of pigmented cells, such as melanocytoma and pigment epithelial tumours. Because of its high vascularity, the risk for profuse hemorrhage during tumour biopsy should be carefully weighed in case of Knapp–Rønne melanoma.

      References

        • Knapp H.
        Vierzehnter Fall. Weisses, vaskulares (telangiektatisches) Sarkom der Aderhaut. Heilung durch Enucleatio bulbi, in Die intraocularen Geschwulste.
        Muller: Carlsruhe. 1868; : 134
        • Ronne H.
        Preretinal choroidal melanosarcoma.
        Acta Ophthalmol (Copenh). 1923; : 268-272
        • Jensen O.A.
        The “Knapp-Ronne” type of malignant melanoma of the choroid. A haemangioma-like melanoma with a typical clinical picture. So-called “preretinal malignant choroidal melanoma.”.
        Acta Ophthalmol (Copenh). 1976; 54: 41-54
        • Laqua H.
        • Volcker H.E.
        Pars plana vitrectomy in eyes with malignant melanoma.
        Graefes Arch Clin Exp Ophthalmol. 1983; 220: 279-284
      1. Pülhorn G, Winter R. Malignes Melanom der Uvea vom Typ “Knapp-Ronne”. Klin Monatsbl Augenheilkd 1976;169(3):352–8