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BACKGROUND: Inflammatory and nested testicular sex cord tumor (IN-SCT) is a newly defined and rare variant of sex cord-stromal tumors, characterized by EWSR1::ATF1 gene fusion, prominent inflammatory infiltration, and aggressive behavior, often leading to misdiagnosis as lymphoma or seminoma. This study aims to systematically analyze the clinicopathological and molecular features of IN-SCT through a case report and comprehensive literature review, exploring its diagnostic pitfalls and therapeutic strategies. CASE PRESENTATION: A 36-year-old male presented with painless left testicular enlargement. Ultrasound revealed a 6.0 × 5.0 × 3.3 cm heterogeneous mass with irregular vascularity. Initial pathological evaluation after radical orchiectomy at an outside hospital favored a diagnosis of seminoma. However, external consultation raised suspicion of ALK-negative anaplastic large cell lymphoma (ALCL) based on CD30 immunoreactivity. Further histopathological examination at our institution revealed tumor cells arranged in nests and solid patterns, with extensive inflammatory infiltration. Immunohistochemistry (IHC) demonstrated weak positivity for inhibin-α and diffuse positivity for CD30. Fluorescence in situ hybridization (FISH) confirmed EWSR1 gene rearrangement, leading to a final diagnosis of IN-SCT. TREATMENT AND OUTCOME: The patient underwent six cycles of platinum-based chemotherapy following orchiectomy. No evidence of recurrence was observed at the 10-month follow-up. CONCLUSION: IN-SCT is a diagnostically challenging tumor characterized by the triad of inflammatory stroma, EWSR1::ATF1 fusion, and aggressive clinical behavior. Accurate recognition of its unique features supports its classification as a distinct entity. Surgical excision followed by adjuvant chemotherapy may benefit patients with advanced disease. The distinct molecular profile of IN-SCT may provide future directions for targeted therapy and diagnostic refinement.
Wang et al. (Wed,) studied this question.