Contributed by Mariana Cajaiba, MD
CLINICAL HISTORY AND PATHOLOGIC FINDINGS
This patient is a 7-month old baby boy who underwent kidney transplantation due to congenital steroid-resistant nephrotic syndrome with progressive renal failure. Additional clinical history included bilateral inguinal exploration followed by right orchidopexy due to cryptorchidism; the left testis had not been found on surgical exploration. Physical examination disclosed a well-developed baby boy with normal male genitalia and a non-palpable left testis.
The renal transplantation procedure was accompanied by bilateral nephrectomy. During the surgery, the left testis was identified in the retroperitoneum and resected. Gross examination disclosed a 1.0 cm testis with a greyish-white well-circumscribed nodule underneath the tunica albuginea, whereas the right kidney was remarkable for a 1.8 cm ovoid mass located on the upper pole, apparently confined to the parenchyma. The remaining testicular and right kidney parenchyma appeared grossly normal, as well as the left kidney.
Microscopic examination of the left testis revealed a neoplasm composed of cystic follicular structures lined by cuboidal epithelium, intermixed with solid areas and foci of immature-appearing stroma (Figures 1, 2, 3, and 4). The cystic structures were filled by eosinophilic proteinaceous material with occasional calcifications; in some areas, these structures appeared to be continuous with the non-neoplastic seminiferous cords. The adjacent testicular parenchyma showed focal cords with abnormal shapes, and a thin, poorly collagenized tunica albuginea (Figure 5).
Histological examination of both kidneys showed several abnormal glomeruli characterized by expansion and sclerosis of mesangial matrix accompanied by podocyte hypertrophy (Figures 6 and 7). Renal tubules showed variable degrees of atrophy and dilation, sometimes with a microcystic aspect (Figure 8). The interstitium was mildly fibrotic. Both kidneys displayed several well-defined areas of immature parenchyma delineating the periphery of renal lobules, characterizing nephroblastematosis (Figure 9). The right kidney tumor consisted predominantly of sheets of immature-appearing small round blue cells in a haphazard pattern, sometimes intermixed with tubular structures (Figure 10).