Diagnosis and Treatment > Signs and Symptoms
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Summary
Silent corticotroph adenoma (SCA) is an unusual type of nonfunctioning pituitary adenoma (NFA) that is silent both clinically and biochemically and can only be recognized by positive immunostaining for ACTH. Under rare circumstances, it can transform into hormonally active disease presenting with severe Cushing syndrome. It might often produce diagnostic dilemma with difficult management issue if not thoroughly investigated and subtyped accordingly following surgery. Here, we present a 21-year-old male who initially underwent pituitary adenomectomy for presumed NFA with compressive symptoms. However, he developed recurrent and invasive macroadenoma with severe clinical as well as biochemical hypercortisolism during post-surgical follow-up. Repeat pituitary surgery was carried out urgently as there was significant optic chiasmal compression. Immunohistochemical analysis of the tumor tissue obtained on repeat surgery proved it to be an aggressive corticotroph adenoma. Though not cured, he showed marked clinical and biochemical improvement in the immediate postoperative period. Anticipating recurrence from the residual tumor, we referred him for cyber knife radio surgery.
Learning points:
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Pituitary NFA commonly present with compressive symptoms such as headache and blurred vision.
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Post-surgical development of Cushing syndrome in such a case could be either drug induced or endogenous.
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In the presence of recurrent pituitary tumor, ACTH-dependent Cushing syndrome indicates CD.
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Rarely a SCA presenting initially as NFA can transform into an active corticotroph adenoma.
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Immunohistochemical marker for ACTH in the resected tumor confirms the diagnosis.
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Summary
Ectopic ACTH/CRH co-secreting tumors are a very rare cause of Cushing’s syndrome and only a few cases have been reported in the literature. Differentiating between Cushing’s disease and ectopic Cushing’s syndrome may be particularly difficult if predominant ectopic CRH secretion leads to pituitary corticotroph hyperplasia that may mimic Cushing’s disease during dynamic testing with both dexamethasone and CRH as well as bilateral inferior petrosal sinus sampling (BIPSS). We present the case of a 24-year-old man diagnosed with ACTH-dependent Cushing’s syndrome caused by an ACTH/CRH co-secreting midgut NET. Both high-dose dexamethasone testing and BIPSS suggested Cushing’s disease. However, the clinical presentation with a rather rapid onset of cushingoid features, hyperpigmentation and hypokalemia led to the consideration of ectopic ACTH/CRH-secretion and prompted a further workup. Computed tomography (CT) of the abdomen revealed a cecal mass which was identified as a predominantly CRH-secreting neuroendocrine tumor. To the best of our knowledge, this is the first reported case of an ACTH/CRH co-secreting tumor of the cecum presenting with biochemical features suggestive of Cushing’s disease.
Learning points:
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The discrimination between a Cushing’s disease and ectopic Cushing’s syndrome is challenging and has many caveats.
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Ectopic ACTH/CRH co-secreting tumors are very rare.
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Dynamic tests as well as BIPSS may be compatible with Cushing’s disease in ectopic CRH-secretion.
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High levels of CRH may induce hyperplasia of the corticotroph cells in the pituitary. This could be the cause of a preserved pituitary response to dexamethasone and CRH.
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Clinical features of ACTH-dependent hypercortisolism with rapid development of Cushing’s syndrome, hyperpigmentation, high circulating levels of cortisol with associated hypokalemia, peripheral edema and proximal myopathy should be a warning flag of ectopic Cushing’s syndrome and lead to further investigations.
