Extrascleral tumor extension associated with localized scleral melt following plaque brachytherapy for uveal melanoma: histopathologic findings

Abstract

Purpose : Scleral necrosis is a known complication of plaque radiotherapy for uveal melanoma, with a reported incidence of 0-27%. The diagnostic dilemma in these cases is whether pigment protrusion represents herniation of necrotic non-viable tumor or active tumor extension. Our retrospective observational study aims to better characterize the clinical and histopathologic features of patients with scleral melt following brachytherapy.

Methods : A retrospective review was performed on 301 patients undergoing I-125 brachytherapy for uveal melanoma. A subset of 31 patients requiring subsequent enucleation was identified and analysis including pathology performed on 6 patients with extrascleral extension associated with scleral necrosis.

Results : Our rate of scleral necrosis was 2% (6/301). In the 6 cases of scleral melt, average age at plaque insertion was 66 y/o (range 54-83). Average follow-up from plaque placement was 65 months (range 32-95) with metastatic disease in 1 patient. No patients had ocular history of scleritis or diseases predisposing to scleral melt. Average initial tumor thickness was 7.1 mm (range 3.1 mm to 10.5 mm). Three tumors were anterior (ciliary body), 1 mid-peripheral, 2 posterior. Gene expression profile (GEP) was class 1A in 1 case, class 1B in 1, class 2 in 3, and 1 unknown. Histologic analysis showed extraocular extension through full-thickness scleral discontinuities. The specimens had varying proportions of morphologically intact tumor that stained positive with Mart-1/tyrosinase-red. Cell type was predominantly epithelioid in 1 and mixed spindle/epithelioid in 5. Mitotic figures were noted in 4 specimens, including 3 eyes exhibiting mitoses within or adjacent to the extrascleral portion of tumor.

Conclusions : Protruding pigmented material at areas of scleral necrosis after plaque radiotherapy may represent herniation of inactive tumor, but in some cases may represent actively proliferating tumor.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Fundus (A,B) and external (C,D) photographs of case 2. Pre-plaque (A) and 11 months post-plaque (B). Sceral necrosis with episcleral nodule 7 months (C) and 19 months (D) post-plaque.

 

H&E sections of enucleated globe. (A) Low-power view showing extrascleral extension through 3 scleral discontinuities (arrows). (B) High-power view of boxed area from (A) showing mitotic figure (arrow) within neck of tumor in region of scleral melt.