Endocrine Abstracts

Introduction: Melanoma is predominantly a skin malignancy, originating from melanocytes. We present a rare case of metastatic primary adrenal melanoma (PAM) mimicking adrenal cortical carcinoma (ACC).

Case report: A 36-year-old male presented with right flank pain, vomiting, pyrexia & 15kg weight loss. CT revealed 6cm adrenal mass; initially treated as an abscess. Despite normal adrenal screening biochemistry & prolonged antibiotics, the mass grew to 8cm, prompting suspicion of ACC. 18^F-FDG PET showed high uptake in adrenal mass with multiple lung & peritoneal deposits. Given adrenal biopsy contraindicated, lung biopsy was undertaken; histology indicated ACC: malignant epithelioid cells with pleomorphism & nuclear inclusions. The patient was informed of metastatic ACC diagnosis & Etoposide-Doxorubicin-Cisplatin-Mitotane (EDP-M) chemotherapy was planned.

Progress: Biopsy immunohistochemistry contradicted histology, demonstrating classic features of melanoma (cytoplasmic staining: MelanA, HMB45 & S100) & absence of adrenal markers; molecular test revealed the most common melanoma mutation: BRAF V600. No evidence of melanoma elsewhere noted. Urine steroid profile ruled out ACC. Melanoma MDT confirmed metastatic PAM & combination immunotherapy of Ipilimumab and Nivolumab was initiated. The patient is doing well on immunotherapy and heading towards disease remission.

Discussion: This case highlights diagnostic challenges of a) benign vs malignant adrenal mass, b) primary ACC vs secondary adrenal metastasis & c) malignancy type identification. Adrenal gland is a recognized metastatic site for melanoma ¹ , but primary site for melanoma origin is exceptionally rare; 23 cases reported in literature.

Possible explanation: Adrenal medullary blasts & melanoblasts have a common embryological origin from neural crest.

Learning points: 1. PAM should be considered as differential diagnosis in unilateral adrenal mass mimicking ACC. 2. To await immunohistochemistry & molecular test results before administering cancer-specific treatment. 3. Urine steroid metabolomics is useful in differentiating ACC from other malignancies/pathologies.

References: 1. Dasgupta T, Brasfield R, Paglia M: Primary melanomas in unusual sites. Surg Gynecol Obstet. 1969, 128: 841-848.