Abstract
Purpose: :
To describe an unreported histopathologic finding following secondary enucleation.
Methods: :
A 20 month old girl was diagnosed with a bilateral sporadic retinoblastoma. Growth pattern was endophytic in the left eye with local vitreous seeds (Group C or Vb) and exophytic in the right eye with complete retinal detachment due to a macular tumor (13.6 x 13.6 mm) overlying the optic nerve head (Group D or Va). At diagnosis, cerebral MRI and lumbar puncture provided no evidence of extraocular involvement.
Results: :
Left eye tumors and vitreous seeds resolved completely following 3 monthly cycles of chemoreduction (VP16 & Carboplatin) and cryotherapy. Right eye (OD) tumors showed complete response to this regimen and focal treatment with cryotherapy, chemothermotherapy, thermotherapy and laser photocoagulation. Fundus OD showed complete reattachment of the retina and a type III regression of the primary tumor, margins of which moved away from the optic disc leaving only a papillo-tumoral cicatricial tract. However, 4 months later, recurrence of a total exudative retinal detachment occurred in OD. Secondary enucleation of OD with 10 mm of optic nerve was performed due to absence of visual potential. On histopathologic analysis, the prelaminar optic nerve was entirely free of tumor cells. The laminar and retrolaminar zones showed a 1.3 mm focus of undifferentiated retinoblastoma cells with high mitotic index as shown by Ki67 antibody staining. Despite 50 serial sections through the optic nerve head, there was no connection between the optic nerve tumor island and any of the intraocular tumors or seeds. The surgical cut end of optic nerve, choroid and sclera were free of tumor. The patient received adjuvant therapy, i.e. 2 monthly cycles of chemotherapy (VP16 & Carboplatin followed by Vincristine & Cyclophosphamide) with an event-free follow-up of 16 months.
Conclusions: :
Isolated involvement of the optic nerve without histopathologic connection with the intraocular tumor mass has never been reported. Laminar and postlaminar optic nerve involvement can occur with tumor free prelaminar zone. This finding reinforces the rule to include a long (10-15 mm) stump of optic nerve in enucleations for retinoblastoma. This also highlights the existence of a subgroup of papillary retinoblastoma with cryptic optic nerve involvement at presentation. Upon regression under chemotherapy these tumors may leave the optic nerve head and still recur in depth of the initial contact zone.
Keywords: retinoblastoma • optic nerve • microscopy: light/fluorescence/immunohistochemistry