Unexpected High-Grade Neuroendocrine Carcinoma in Lung Explant

Abstract

<h3>Introduction</h3> Rarely, malignancies are incidentally detected in lung transplant (LT) explants. These can remain unidentified before LT due to significant architectural distortion of the lung parenchyma, despite appropriate radiographic surveillance. <h3>Case Report</h3> We present the case of a 74-year-old man with history of bilateral LT (03/2021), complicated by grade 2 primary graft dysfunction, for fibrotic hypersensitivity pneumonitis after which a high-grade neuroendocrine carcinoma was unexpectedly found in the right explanted lung. The tumor was 2.1 cm and 3/11 peribronchial lymph nodes were positive for metastatic carcinoma. The left lung explant was negative for malignancy. The tumor was strongly positive for TTF-1 and synaptophysin (<b>Figure 1</b>) with dot-like positivity of the pancytokeratin (AE1/AE3) and CAM 5.2 stains. Tumor cells were negative for CD45, PHH3 demonstrated >50 mitoses/10 high-power fields, and MIB-1 highlighted approximately 60% of tumor nuclei. Whole-body imaging was negative for other masses or acute processes. Maintenance immunosuppression was decreased, and the patient was discharged after LT in stable condition with need for outpatient oncology follow-up. Given the aggressive nature of the explant tumor, the patient decided to pursue adjuvant chemotherapy after recovery from the early post-LT period. The patient received 2 cycles of carboplatin/etoposide, but further treatment was stopped due to severe pancytopenia and need for blood products including platelets. At 6 months post-LT, allograft function is stable - FEV₁ at 2.56 L (88%) - with no evidence of acute cellular rejection or antibody-mediated rejection. There is no evidence of cancer recurrence. <h3>Summary</h3> This is a rare case of high-grade neuroendocrine carcinoma in a lung explant after LT. Recommended etoposide/platinum-based chemotherapy may be limited by adverse effects. Prognosis and feasibility of adjuvant chemotherapy after LT is insufficiently understood.