Hereditary leiomyomatosis and renal cell cancer (HLRCC) is caused by heterozygous germline variants in the fumarate hydratase (FH) gene and is associated with increased susceptibility to cutaneous leiomyomas, uterine leiomyomas, and renal cell carcinoma (RCC). HLRCC-associated RCC usually occurs in the middle age, with the median age being 40–44 years. This report describes a seven-year-old (84-month-old) male who developed a large right kidney tumor with multiple cystic lesions that contained enhanced solid components. There was no evidence of distant metastasis. The male patient underwent right nephrectomy and has been recovering well without metastasis or recurrence. Pathological examination revealed that tumor cells with relatively prominent nucleoli and surrounded by halos, were located in a limited area. Immunohistochemical staining was negative for FH. Whole-exome sequencing identified his germline variant in the FH gene and its loss of heterozygosity in the tumor. At nine years (114 months) of age, the male patient showed no recurrence of the tumor. This was the youngest-onset case of HLRCC-associated RCC to date. This report may affect the starting age for future RCC-surveillance programs for patients with HLRCC.

遗传性平滑肌瘤病和肾细胞癌 (HLRCC) 是由富马酸水合酶( FH) 基因，并且与皮肤平滑肌瘤、子宫平滑肌瘤和肾细胞癌 (RCC) 的易感性增加有关。HLRCC 相关 RCC 通常发生在中年，中位年龄为 40-44 岁。这份报告描述了一名 7 岁（84 个月大）男性，他出现了一个大的右肾肿瘤，伴有多个囊性病变，其中包含增强的实性成分。没有远处转移的证据。男性患者接受了右肾切除术，目前恢复良好，未发生转移或复发。病理检查显示，肿瘤细胞核仁比较突出，周围有光晕，分布范围有限。FH 免疫组化染色阴性。全外显子组测序鉴定了他在FH中的种系变异基因及其在肿瘤中杂合性的丧失。在 9 岁（114 个月）时，男性患者的肿瘤没有复发。这是迄今为止最年轻的 HLRCC 相关 RCC 病例。该报告可能会影响 HLRCC 患者未来 RCC 监测计划的开始年龄。