metastatic disease is rare and usually occurs within the first two years after initial diagnosis , and is extremely rare after that time period . however , metastases to forearm bones are very rare with only very few reports published till date . here we present a case of bilateral retinoblastoma with metastases to right forearm bones four years after the initial treatment . an 8-year - old boy treated four years back for bilateral retinoblastoma with enucleation of left eye along with adjuvant chemotherapy and radiotherapy presented with a right forearm swelling . an x - ray revealed a mass lesion in right forearm with destruction of lower one third of right ulna . bone scan was performed three hours after intravenous injection of 5 mci of 99tc mdp . whole body images showed increased tracer uptake in right forearm bones [ figure 1 ] . static images revealed increased tracer uptake in middle and lower one - third of right ulna consistent with x - ray findings . in addition , bone scan showed involvement of lower one - third of left radius . however , special stains excluded ewing 's sarcoma and other primitive neuroectodermal tumors ( pnets ) . involvement of radius picked up by bone scan had important implication in deciding the nature of disease as ewings tumor with multi - focal disease as second primary is very unlikely . tc99m - mdp bone scan ; ( a ) whole body anterior view ; ( b ) whole body posterior view showing increased tracer uptake in right forearm bones . static images of bilateral forearms ; ( c ) anterior ; ( d ) posterior revealing involvement of right ulna and radius osseous metastases from retinoblastoma are reported most commonly in the skull and long bones . the prognosis for most children diagnosed with retinoblastoma is good , with a 5-year survival of rate of more than 90% . complications include local recurrence , metastases , and the development of a second primary tumor . focal and diffuse involvement of the bones and bone marrow is known to occur , but metastases are usually seen within two years of initial diagnosis and later metastases are said to be extremely rare . these patients are also at risk of increased second primaries like osteosarcoma , leiomyosarcoma , spindle cell sarcoma , malignant fibrous histiocytoma , rhabdomyosarcoma , angiosarcoma , ewing sarcoma , and pnet . these typically develop after a latent period of 815 years.[68 ] involvement of multiple bones would point the diagnosis towards metastases rather than multifocal second primary . imaging modalities available for skeletal metastatic work up include x - ray , ct , mri and functional imaging modalities like bone scan . x - rays are in general less sensitive to pick up the metastases , whereas whole body mri is not widely available , so conventional wb bone scan is essential in the metastatic work up of these patients . in our case , x - ray picked up ulnar involvement but radius involvement was missed . however , bone scan revealed radius involvement suggesting a metastatic disease rather than second primary . later , histopathology revealed round blue cell tumour involving both radius and ulna and ihc was negative for cd99 excluding diagnosis of ewings sarcoma . skeletal scintigraphy remains an essential diagnostic procedure in evaluation of these patients and can have important implications in management .
osseous metastases from retinoblastoma , the most common ocular malignant neoplasm of childhood , are reported most commonly in the skull and long bones . 
 however , metastases to forearm bones are very rare . here 
 we present a case of bilateral retinoblastoma with metastases to right forearm bones four years after the initial treatment .