Case presentation
A 7-year-old Japanese male presented with a right upper abdominal mass.
He had no remarkable past medical history. His parents were
non-consanguineous. His father underwent prostatectomy for prostate
cancer at age 51. His mother and his elder brother had no remarkable
medical history (Fig. 1A ). His general condition was good.
Physical examination revealed a large mass in the right upper abdomen.
Brown spots were found on the left shoulder, lower back, and lower
abdomen. His laboratory tests were normal, except for mildly elevated
C-reactive protein (1.30 mg/dL). An enhanced computed tomography (CT)
scan showed a large right kidney tumor with multiple cystic lesions that
contained enhanced solid components (Fig. 1B ) and a
compensatory hypertrophic left kidney. Although he was initially
misdiagnosed with multicystic dysplastic kidney (MCDK),18F-fluorodeoxyglucose-positron emission tomography
(FDG-PET) revealed uptake on the solid components of the right kidney
(Fig. 1C ). Renal scintigraphy showed decreased right kidney
function. There was no evidence of distant metastasis by enhanced CT and
FDG-PET.
We performed a laparoscopic right nephrectomy. The tumor was inside the
kidney with multiple cysts and focal nodules. Pathological examination
revealed that cysts were lined by mild eosinophilic simple cuboidal
epithelium with mild nuclear atypia and hardly mitotic activity. Tumor
cells with relatively prominent nucleoli, surrounded by halos, were
located in the limited area (Fig. 1D ). Mild eosinophilic
inorganic materials accumulated in a portion of the cysts. Continuous
with the cysts, eosinophilic cells showed a papillary growth pattern
with a thin vascular core. A nodular area and around the cysts showed a
tubular structure and solid thick growth pattern. Multiple lesions were
detected inside the kidney, suggesting a tumor of multifocal origin. The
resected edge had no tumor cells. All of the hilar lymph node samples
were negative for metastases. The Transcription factor E3 split
signal was negative in fluorescent in situ hybridization, and the
Ki-67 expression was 2%–3%. Immunohistochemical staining was
diffusely positive for succinate dehydrogenase B, a cluster of
differentiation (CD) 10, epithelial membrane antigen, and paired box 8
and partially positive for pan-cytokeratin (AE1/AE3) and
alpha-methylacyl coenzyme A racemase. The staining was negative for
cytokeratin 7, carbonic anhydrase 9, CD117, transcription factor EB, and
FH (Fig. 1E ). On the basis of these findings, the tumor was
pathologically diagnosed with HLRCC-associated RCC. Two years later,
abdominal MRI and chest CT showed no postoperative recurrence or
metastasis of the tumor, and no appearance of left renal or skin
lesions.