Robert S. Wang

Both embryonic-type neuroectodermal tumor and nephroblastoma arising as somatic-type malignancies are rare, particularly nephroblastoma. Concurrent embryonic-type neuroectodermal tumor and nephroblastoma have only been reported once in literature, identified in metastatic pelvic lymph nodes in association with a mixed germ cell tumor. Herein, we report the first concurrent embryonic-type neuroectodermal tumor and nephroblastoma within the primary testicular tumor, arising associated with a mixed germ cell tumor. A 36-year-old man presented with a 4.5 cm right testicular mass. He underwent right orchiectomy. Gross examination revealed a well-circumscribed, solid to cystic mass confined to the testis (pT1). Histological examination demonstrated a mixed germ cell tumor composed of teratoma (40% of the tumor mass), seminoma (10%), embryonal carcinoma (2.5%), and yolk sac tumor (2.5%), with associated germ cell neoplasia in situ. Additionally, two somatic-type malignancy components were identified, including embryonic-type neuroectodermal tumor (40%) and nephroblastoma (5%). The embryonic-type neuroectodermal tumor consisted of primitive neural tubules, rosettes, and blastemal cells. The nephroblastoma was composed of tubules, blastemal cells, and stromal cells. Immunohistochemically, the embryonic-type neuroectodermal tumor showed diffuse positivity for SOX11, with focal expression of synaptophysin and CD99, while the nephroblastoma was positive for PAX8 and WT1. The patient developed metastasis to a retroperitoneal lymph node 1 month after the orchiectomy, subsequently received chemotherapy, and is alive without metastatic disease at 13 months of follow-up.

Purpose: ^99mTc-sestamibi single-photon emission CT/x-ray CT (SPECT/CT) uses a mitochondria-targeting tracer to differentiate renal cell carcinoma from oncocytomas and hybrid oncocytoma/chromophobe tumors. Initial studies support ^99mTc-sestamibi SPECT/CT’s accuracy, but we previously found that oncocytomas still account for 20% of lesions with low tracer uptake in qualitatively interpreted scans. Here, we assess performance of ^99mTc-sestamibi SPECT/CT utilizing quantitative assessment thresholds, hypothesizing that this may improve test performance. Materials and Methods: All ^99mTc-sestamibi SPECT/CT performed for renal mass evaluation between February 2020 and December 2021 was analyzed. A “hot” mass had qualitatively equivalent or higher ^99mTc-sestamibi uptake than normal renal parenchyma; a “cold” mass did not. Target-to-background ratios (TBRs) were calculated using tracer counts in the masses vs nearby normal parenchyma. Quantitative “hot”/“cold” determinations were made using published TBR cutoffs. Findings were correlated with histology. Results: Seventy-eight patients underwent ^99mTc-sestamibi SPECT/CT for 98 renal masses. For the 52 masses with diagnostic pathology, the negative predictive value (NPV) of qualitatively interpreted ^99mTc-sestamibi SPECT/CT for ruling out oncocytoma was 80%, with a 1.9% false-positive rate. A TBR cutoff of 0.46 achieved the highest NPV of 89.3%, with a 23.1% false-positive rate. A TBR cutoff of 0.74 achieved the lowest false-positive rate of 1.9%, with a 78.3% NPV. No TBR cutoff achieved both higher NPV and lower false positives than the qualitatively interpreted scans. Conclusions: Quantitative TBR cutoffs for interpretation of ^99mTc-sestamibi SPECT/CT scans for renal masses do not offer meaningful improvements in accuracy over qualitative reads. Additional studies are required to better characterize the utility of ^99mTc-sestamibi SPECT/CT in the real-world setting.