Primary intrarenal yolk sac tumor.

Extragonadal germ cell tumors (EGGCTs) usually are not coexistent with a gonadal tumor, hence in a way, are primary and are rare. The origin of primary EGGCT is still a matter of debate. Herewith, we report a patient with primary intrarenal yolk sac tumor in a 43-year-old man. The purpose of this report is to add a rare tumor to the differential diagnosis of renal neoplasms.

INTRODUCTION

Yolk sac tumor (endodermal sinus tumor) (YST) is a malignant germ cell tumor that usually arises in the gonads. Rare occurrence of extragonadal germ cell tumors is known to occur in the mediastinum, retroperitoneum, sacrococcygeal region, and pineal gland.[1] We report an isolated intrarenal YST in an adult who presented with a renal mass.

CASE REPORT

A 43-year-old male presented with left upper abdominal pain, mildly tender palpable mass, normal genitals, and unremarkable previous surgical issues. Imaging revealed bilateral renal calculi along with grossly enlarged, calculi laden, hydronephrotic left kidney, intrarenal mass lesion of renal pelvis, and perinephric stranding. Multiple enlarged necrotic retroperitoneal nodes were noted [Figure 1].

Figure 1

Contrast enhanced computed tomography scan showing heterogeneous mass in the left renal pelvis (thick white arrow) with multiple calculi with gross hydronephrosis with thinned out parenchyma with paraaortic lymphadenopathy (thin white arrow)

With the clinical suspicion of xanthogranulomatous pyelonephritis with squamous metaplasia/carcinoma, open left radical nephrectomy, and excision of palpable retroperitoneal nodes was performed.

Histopathological examination revealed high-grade malignant germ cell tumor with features favoring for YST (Schiller-Duval body, microcytic, and solid pattern along with hyaline globules stained dark pink on D-PAS stain) with positive metastatic nodes. Immunohistochemistry confirmed YST (alpha-fetoprotein [AFP], cytokeratin, placental-like alkaline phosphatase, CD30, glypican 3 positivity and negative for c-kit and beta-human chorionic gonadotropin [HCG]) [Figure 2]. Subsequent scrotal ultrasonography did not show echogenicity/scars. Serum AFP levels of 2640 ng/mL with normal beta-HCG and lactate dehydrogenase levels. The patient has been advised adjuvant chemotherapy.

Figure 2

Histopathological images, (a) low power view of the entire tumor depicting microcytic and solid pattern, (b) high power view showing Schiller-Duval bodies (thick arrow) and hyaline globules stained dark pink on D-PAS stain (thin arrow); immunohistochemistry images, (c) alpha-fetoprotein positive, (d) placental alkaline phosphatase positive and (e) glypican 3 positive

DISCUSSION

Extragonal YST is rare and intrarenal tumor has been reported in pediatric age group.[2345] To the best of our knowledge, this is the first reported case of an intrarenal YST in adults. The purpose of this report is to add a rare tumor to the differential diagnosis of renal neoplasms.