Supplementary Material for: Ectopic ACTH-dependent Cushing’s syndrome Emerging at a Late Stage of a Mixed Histology Neuroendocrine Neoplasm: a case report

Introduction:
Neuroendocrine neoplasms (NENs) encompass well-differentiated tumors (NETs) and poorly differentiated carcinomas (NECs), which are distinguished by their clinical behavior and molecular characteristics. They can cause paraneoplastic syndromes, such as ectopic adrenocorticotropic hormone (ACTH) dependent Cushing’s syndrome, necessitating prompt recognition and management due to severe hypercortisolism.

Case presentation:
A 66-year-old patient with a 3-year history of metastatic mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) with a neuroendocrine carcinoma (NEC) and adenocarcinoma component originating from the vulva presented to the emergency department with dyspnea and fatigue. Upon clinical examination, we found widespread hyperpigmentation, a moon-face appearance, hirsutism, buffalo hump, and muscle atrophy.

Laboratory investigations revealed severe hypokalemia (2.3 mmol/L), elevated serum cortisol (1726 nmol/L) and ACTH (194 ng/L) levels. Urinary free cortisol (UFC) measurement was 21-fold the upper limit of the reference range (3614.0 nmol/24h), and cortisol concentration did not decreases after 1mg-dexamethasone suppression test (1812 nmol/L for an expected value < 50 nmol/L), confirming the ACTH-dependent Cushing's syndrome (CS).

Thoracoabdominal computed tomography (CT) scan demonstrated progressive neoplastic disease in the liver, kidney, lymph nodes, peritoneum and lungs. Brain magnetic resonance imaging (MRI) indicated multifocal metastatic infiltration, but no evidence of pituitary adenoma. (Figure 1.)

Interestingly, despite a previously negative 68Ga-DOTATATE Positron Emission Tomography (PET)/CT performed one year prior, there was moderate somatostatin receptor (SSTR) expression in lymphatic, pulmonary, peritoneal and bone tissues, suggesting the presence of a component with redifferentiation and re-expression of the SSTR. (Figure 2.)

After the work-up, the patient was admitted to a supportive care facility. Hypercortisolism symptoms were effectively managed with an adrenal enzyme inhibitor (ketoconazole) in combination with somatostatin (SST) analogs. Unfortunately, the patient was too frail to benefit from Peptide Receptor Radionuclide Therapy (PRRT).

Conclusion:
This redifferentiation phenomenon in neuroendocrine tumors should be further investigated, as patients might be, under certain conditions, eligible for PRRT. Therefore, we suggest that newly occurring paraneoplastic syndromes in patients with NEC should always be evaluated using 68Ga-DOTATATE PET/CT.

引言：
神经内分泌肿瘤（Neuroendocrine neoplasms, NENs）涵盖高分化肿瘤（神经内分泌瘤，Neuroendocrine tumors, NETs）与低分化癌（神经内分泌癌，Neuroendocrine carcinomas, NECs），二者可通过临床行为及分子特征加以区分。此类肿瘤可引发副肿瘤综合征，例如异位促肾上腺皮质激素（adrenocorticotropic hormone, ACTH）依赖性库欣综合征，由于会导致严重的皮质醇增多症（hypercortisolism），因此需及时识别并予以处理。

病例报告：
一名66岁患者，有3年转移性混合性神经内分泌-非神经内分泌肿瘤（mixed neuroendocrine-non-neuroendocrine neoplasm, MiNEN）病史，该肿瘤起源于外阴，包含神经内分泌癌（NEC）与腺癌两种组分，因呼吸困难及乏力前往急诊就诊。临床检查可见全身广泛色素沉着、满月脸、多毛症、水牛背及肌肉萎缩。

实验室检查结果显示严重低钾血症（血钾2.3 mmol/L），血清皮质醇（1726 nmol/L）与ACTH（194 ng/L）水平升高。尿游离皮质醇（urinary free cortisol, UFC）检测值为参考范围上限的21倍（3614.0 nmol/24h）；1mg地塞米松抑制试验后，皮质醇浓度未出现下降（预期值<50 nmol/L，实测值为1812 nmol/L），证实为ACTH依赖性库欣综合征（Cushing's syndrome, CS）。

胸腹计算机断层扫描（computed tomography, CT）显示肝、肾、淋巴结、腹膜及肺部存在进展性肿瘤病变。脑部磁共振成像（magnetic resonance imaging, MRI）提示多灶性转移浸润，但未发现垂体腺瘤证据（图1）。

值得注意的是，尽管患者1年前行68Ga-DOTATATE正电子发射断层扫描（positron emission tomography, PET）/CT检查结果为阴性，但淋巴、肺、腹膜及骨组织中可见中等程度的生长抑素受体（somatostatin receptor, SSTR）表达，提示存在肿瘤再分化并重新表达SSTR的组分（图2）。

完成相关检查后，患者转入支持治疗机构。高皮质醇血症症状通过肾上腺酶抑制剂（酮康唑）联合生长抑素（somatostatin, SST）类似物得到有效控制。遗憾的是，患者身体状况过于虚弱，无法从肽受体放射性核素治疗（peptide receptor radionuclide therapy, PRRT）中获益。

结论：
该神经内分泌肿瘤的再分化现象有待进一步研究，因为在特定条件下患者可能符合PRRT治疗指征。因此，我们建议对于神经内分泌癌患者新发的副肿瘤综合征，均应采用68Ga-DOTATATE PET/CT进行评估。