6485 Unilateral Adrenal Metastasis From Unknown Primary Carcinoma Mimicking Primary Adrenocortical Carcinoma

Abstract

Abstract Disclosure: S. Watanabe: None. S. Suzuki: None. K. Ishiwata: None. Y. Yamazaki: None. H. Sasano: None. K. Yokote: None. Background: Adrenal metastasis from carcinomas of the lung, breast, and melanoma are observed. However, isolated adrenal metastasis with unknown primary carcinoma origin has been rare, and the diagnosis is challenging. We encountered a case of unilateral adrenal tumor clinically diagnosed as non-functional primary adrenocortical carcinoma, but found to be a metastatic tumor on postoperative pathology. Clinical Case: A 68-year-old man was referred to our hospital for examination of an 8mm right adrenal incidentaloma. He underwent hormone therapy for prostate cancer four years ago, and the condition is in remission with no recurrence signs. Follow-up CT revealed that the adrenal tumor rapidly enlarged from 8 mm to 36 mm within six months, and its mean attenuation value was 38 HU. MRI showed that the adrenal tumor had a low signal intensity on T1 and a high signal on T2. At the same time, there is mediastinal lymphadenopathy and a 9-mm nodule in the lower lobe of the right lung, which was considered benign from the stable condition. FDG-PET/CT showed FDG uptake only in the right adrenal tumor (maximum standardized uptake value of 21.39). [1]23I-MIBG scintigraphy did not show any accumulations. The serum and urinary adrenal hormones were all within normal limits. Notably, tumor markers such as prostate-specific antigen (PSA), carcinoembryonic antigen (CEA), α-fetoprotein (AFP), and cancer antigen 19-9 (CA 19-9) were all within normal ranges. Therefore, we clinically suspected non-functional primary adrenocortical carcinoma, and the laparoscopic right adrenalectomy was performed. The resected right adrenal lesion was encapsulated and measured 79×54×22 mm. On histological analysis, the nodule comprised tumor cells with eosinophilic cytoplasm, and abundant tissue infiltrating lymphocytes. Immunohistochemical studies revealed that the tumor was not of adrenal origin due to negative steroidogenic factor-1 (SF-1) and inhibin alpha staining. From these results, the adrenal tumor was diagnosed as adrenal metastasis from unknown primary carcinoma. The tumor cells were positive for cytokeratin19, CEA, and thyroid transcription factor-1 but negative for PSA, p63, cytokeratin 5/6, insulinoma-associated protein-1, and synaptophysin. Genetically, the adrenal tumor harbored genomic abnormalities in CDKN2A, TP53, NF1, PBRM1, and KEAP1 genes. Conclusion: Isolated adrenal metastasis without a detectable primary tumor is rare but should be considered a differential diagnosis in the case of an enlarged, non-functioning adrenal tumor. Adrenalectomy or tumor biopsy may be actively considered to diagnose and determine the optimal course of treatment. Presentation: 6/3/2024