Somatostatin-receptor-negative carcinoid tumour responsible for Cushing's syndrome

Cushing's syndrome due to adrenocorticotropic hormone-secreting metastatic neuroendocrine tumor of unknown primary origin: a case report and literature review

BACKGROUND

In this article, we present a case of neuroendocrine neoplasm of unknown primary origin (UPO NEN), which is a rare cause of ectopic Cushing's syndrome (ECS) presenting numerous challenges, together with a literature review.

CASE REPORT

A 43-year-old male patient presented with clinical features consistent with Cushing's syndrome (CS) and adrenocorticotropic hormone (ACTH)-dependent hypercortisolemia. Despite a suspicious lesion on pituitary MRI, the high-dose dexamethasone suppression test and bilateral inferior petrosal sinus sampling results were not compatible with Cushing's disease. Bilateral non-homogeneous opacities were observed in the thorax CT of the patient, who also had a history of COVID-19 infection, but no tumoral lesion was detected. When ⁶⁸Ga-SSTR PET/CT and ¹⁸FDG-PET/CT were performed, multiple metastatic foci were detected in mediastinal and hilar lymph nodes and the axial skeleton. Paratracheal-subcarinal lymph nodes were excised mediastinoscopically, and the diagnosis of NEN was made. Histopathological findings indicated that the possible origin was an atypical pulmonary carcinoid with a low Ki-67 labeling index. After controlling hypercortisolemia, a regimen of somatostatin analogs and capecitabine plus temozolomide was decided upon as treatment by a multidisciplinary council.

CONCLUSION

This is a challenging case of UPO NEN presenting with ECS and confounding factors, such as previous infection and incidental lesions, during the diagnosis process. The case in question highlighted the fact that atypical pulmonary carcinoid with a low proliferation index may cause visible metastases even when radiologically undetectable.

Location of ectopic adrenocortical hormone-secreting tumors causing Cushing's syndrome in the paranasal sinuses

BACKGROUND

The majority of ectopic adrenocorticotropic hormone (ACTH)-secreting tumors are localized in the chest or abdomen. Occasionally, these tumors are found in the paranasal sinuses.

METHODS

We present 2 unusual cases of ectopic ACTH syndrome whose ACTH-secreting tumors were localized in the paranasal sinuses and describe their biochemical and radiological presentation.

RESULTS

The first patient had an ACTH-secreting olphactory neuroblastoma originating in the ethmoid sinuses. The second patient had a clinical course and biochemical findings indistinguishable from pituitary ACTH-dependent Cushing's syndrome, except for negative petrosal sinus sampling. Head imaging showed a "polyp" in the left maxillary sinus-secreting ACTH. Both patients went into remission following surgical resection and recovered normal pituitary-adrenal axis function.

CONCLUSION

Ectopic ACTH secretion may originate from lesions in the paranasal sinuses. This accessible location allows for direct immunohistochemical diagnosis with ACTH staining. Surgical resection/radiation therapy can result in complete remission of the disease and restoration of normal pituitary-adrenal function.