A Case of Non-Irradiated Balloon Cell Melanoma of the Choroid: Expanding the Morphological Spectrum of Primary Uveal Melanomas

Abstract

Uveal melanoma (UM) is the most common primary intraocular tumor in adults and usually has a very poor prognosis. Histologically, UMs have been classified in epithelioid cell type, spindle cell type, and mixed cell type. Balloon cells are large pale cells that contain small, hyperchromatic, central nuclei with vesiculated, clear, and lipid-rich cytoplasm. A balloon cell morphology is infrequently observed in naevi and even less frequently in malignant melanomas of the skin, conjunctiva, ciliary body and choroid. In this regard, UMs that exhibit balloon cell features are generally those previously treated with proton beam irradiation and then enucleated, rather than those that directly underwent primary surgery. To the best of our knowledge, very few cases of primary UM showing extensive balloon cell morphology have been reported in scientific literature to date. We herein present an unusual case of primary UM with diffuse balloon cell changes in a 69-year-old woman.

Keywords: balloon cell; eye tumor; non-irradiated melanoma of the choroid; uveal melanoma.

Figure 1

MR findings. Axial (A) T2-weighted turbo spin-echo STIR and (B) fat-suppressed T1-weighted images show a lentiform-shaped intraocular mass along the postero-lateral aspect of the left globe (white arrows), adjoining the optic disk. The lesion exhibits intermediate signal intensity on both T1- and T2-weighted images, a finding consistent with poorly pigmented melanoma. On (C) axial contrast-enhanced fat-suppressed T1-weighted image, the neoplasm demonstrates marked enhancement (white arrow). On (D) axial DW image (b = 1000 s/mm²) and (E) corresponding ADC map, the tumor displays restricted diffusion with high signal intensity on DWI image and low signal intensity on ADC map (white arrows), a finding consistent with hypercellularity. (F) The ADC value was 840 × 10⁻⁶ mm²/s.

Figure 2

(A) Low magnification showing an ovoidal-shaped, poorly-pigmented choroidal tumor of the posterior ocular chamber (hematoxylin and eosin; original magnification 25×). (B) Due to the mass effect, the lesion induces a massive retinal detachment (hematoxylin and eosin; original magnification 50×). (C) Tumor exhibits a diffuse ballooning morphology, consisting of medium-sized, ovoidal cells with abundantly to weakly clear eosinophilic granular cytoplasm; few pigmented melanophages are also seen (hematoxylin and eosin; original magnification 400×). (D) A small portion of the neoplasm is composed of more pigmented spindle-shaped cells with elongated nuclei and conspicuous nucleoli (hematoxylin and eosin; original magnification 150×). Neoplastic cells are consistently negative for PAS (E) and BAP-1 (F) immunostaining. (E), periodic acid–Schiff staining; (D), immunoperoxidase; original magnifications 300×.