A. Leiomyosarcoma
The patient underwent a transvenous biopsy with an inferior vena cava filter, and pathology results were consistent with a leiomyosarcoma (LMS), grade 3. Computed tomography results of the chest, abdomen, and pelvis were negative for metastatic disease. She subsequently underwent a radical resection of the pelvic mass, which revealed a 4-cm mass deriving from and encapsulating the right external iliac vein with R1 margins, which was replaced with an interposition graft.
Retinoblastoma is the most common pediatric ocular tumor. The hereditary variant, which is caused by germline variations to the tumor suppressor gene RB1, comprises 40% of all retinoblastoma and is generally associated with bilateral disease.1 Long-term survival of these patients is typically excellent; however, there remains a 33.1% risk of developing a secondary cancer.2,3 This has important implications for monitoring survivors of hereditary retinoblastoma. The median time to development of a subsequent cancer is 18.9 years, and bone and soft-tissue sarcomas comprise most (40%-60%) subsequent cancers, followed by melanoma, accounting for approximately 10%.3 Among soft-tissue sarcomas (STS), LMS is most common, comprising at least 40% of all STS diagnosed in patients with retinoblastoma with a median age at presentation of approximately 32 years.3 Other commonly diagnosed subsequent STS include fibrosarcoma, undifferentiated pleomorphic sarcoma, and rhabdomyosarcoma.3 Prior treatment with radiation or chemotherapy may increase the risk of a subsequent cancer.4 Radiotherapy is a risk factor for developing a subsequent cancer within the treatment field, and alkylating agents, in particular, seem to increase systemic risk of subsequent cancer. Patients who were treated with radiotherapy and an alkylating agent before age 1 year, as with this patient, may have up to 3.8 times greater risk of developing LMS.4