Introduction: Black adrenal adenomas are rare and benign. They are named after their black appearance, due to lipofuscin pigment. Most frequently black adenomas are associated with ACTH-independent Cushings syndrome. They can also cause primary hyperaldosteronism or be nonfunctioning. Unlike most other adrenal adenomas, black adenomas exhibit high Hounsfield units (>30) on CT, and high standard uptake value on FDG-PET.
Case presentation: A 67-year-old woman was diagnosed with lung cancer (adenocarcinoma). For staging purposes, she underwent thoraco-abdominopelvic CT and FDG-PET/CT scans. The CT scan identified a 14 mm nodule of the left adrenal gland, with spontaneous density of 34 Hounsfield units, and the PET/CT scan showed high uptake on the left adrenal gland (maximum standardized uptake value 5.3), but no significant uptake on the pulmonary nodule. Due to high suspicion for metastasis, she underwent an adrenal biopsy. Histological findings were suggestive of an adrenal oncocytoma (oncocytic cells, intracytoplasmic lipofuscin pigment, nuclear anisocarysosis, binucleation, prominent nucleolus and nuclear pseudoinclusions). She underwent an upper right lobectomy and was restaged to pT1bN0R0. The adrenal nodule was initially on active surveillance, but due to increasing dimensions to 20 mm on a follow-up CT-scan, she underwent a left adrenalectomy. No hormonal study was performed prior to the biopsy or surgeries. Macroscopically, a dark, homogeneous, well delimited lesion of 1.8×1.8×1.5 cm was identified on the surgical specimen. The histological exam was compatible with an adrenal cortex black adenoma, with a conventional Weiss score of 2. Eleven days after the adrenalectomy, the patient presented to the emergency room with fatigue, abdominal pain, hypotension, and hyponatremia. She had rubeosis faciei and abdominal fat deposition, but no other stigmata of Cushings syndrome. Occasional serum cortisol was 1.8 µg/dl and 1.5 µg/dl, at 5 A.M. and 7 A.M. respectively. A diagnosis of acute adrenal insufficiency was made, and the patient received intravenous hydrocortisone, which was weaned to a physiologic oral dose during one week of hospitalization. The onset of adrenal failure after unilateral adrenalectomy with an intact contralateral adrenal gland, led the medical team to presume a previously undiagnosed endogenous hypercortisolism in relation to the adrenal black adenoma. Recovery of the axis has not been assessed yet.
Conclusion: Black adenomas are benign but present with features suggestive of malignancy on both PET and CT scans. They can be associated with hypercortisolism and hyperaldosteronism. This case highlights the importance of performing hormonal studies despite high suspicion for primary or secondary malignancy.
13 May 2023 - 16 May 2023