T-cell lymphoma of the breast and ovary presenting as a second malignant neoplasm in a pediatric leukemia survivor: A case report and literature review.

Second malignant neoplasms (SMNs) are rare but serious late effects in childhood acute lymphoblastic leukemia (ALL) survivors. Mature peripheral T-cell lymphomas involving both the breast and ovary are exceedingly rare, and their relationship with germline predisposition variants remains poorly understood. We report a 17-year-old female, previously treated for high-risk B-cell ALL and in sustained remission, who developed bilateral breast and ovarian masses in 2024. Histopathology and immunohistochemistry confirmed a mature T-cell lymphoma (CD7+, CD99+, weak CD5/CD3, Ki-67 >90%, TdT-). Whole-exome sequencing revealed a germline pathogenic BRCA2 variant (c.1910-2A>T) along with additional likely pathogenic variants (CUX1, MED12L, POLR3B, PIK3CA). The disease progressed rapidly despite CHOP chemotherapy, and the patient died shortly after diagnosis. This report describes an exceptionally rare SMN of peripheral T-cell lymphoma with breast and ovarian involvement in a pediatric leukemia survivor. The coexistence of a germline BRCA2 mutation and additional genomic alterations suggests a multigenic predisposition hypothesis. Early incorporation of next-generation sequencing may uncover molecular vulnerabilities and inform alternative therapeutic strategies in refractory hematologic malignancies.