Session: MON 306-326-Neoplasia of Endocrine Tissues: Case Reports
Poster Board MON-314
Thymic Carcinoid (TC) tumor presenting as ectopic ACTH syndrome carries poor prognosis. Limited data is available making the treatment approach very challenging.
46 year Caucasian male presented with typical signs and symptoms of Cushing's syndrome(CS).Initial tests were consistent with ACTH-dependent CS: elevated 24hr urine cortisol secretion(1269mcg/d,n<60mcg/d), abnormal 1 mg dexamethasone overnight test(23.5mcg/dl,n<1.8mcg/dl), ACTH 44 pg/ml(n 0-46pg/ml). Pituitary MRI was normal. Inferior petrosal sinus sampling showed no gradient between central and peripheral ACTH levels suggesting ectopic ACTH syndrome.
CT Chest Abdomen showed a large anterior mediastinal mass and multiple osseous metastases to the spine. Octreoscan was negative.He underwent robotic resection of anterior mediastinal mass. Pathology revealed 5.9 cm atypical carcinoid tumor (well-differentiated neuroendocrine carcinoma), with angiolymphatic invasion and positive margins. Ki67 was positive in 10-14% of cells.
He received radiation therapy to the spine and zoledronic acid. Chemotherapy was not given due to apparent absence of signigicant disease progression. Despite therapy with ketoconazole and mitotane 24hr urine cortisol continued to remain elevated. Now bilateral adrenalectomy is being planned.
We present a case of ectopic ACTH syndrome from atypical TC tumor. TCs are the least common tumors accounting for 2-5% of relatively rare primary thymic neoplasms(0.2-1.5% of all malignancies) with neuroendocrine differentiation which typically present in the anterior mediastinum. The diagnosis of a carcinoid–related CS may be difficult because ACTH production can be suppressed by dexamethasone unlike other tumors that produce ectopic ACTH. TCs exhibit relatively aggressive clinical behavior and high propensity for locoregional invasion, local recurrence and distant metastases by hematogenous and lymphatic routes. 20-40% have distant metastases at presentation. Since most TCs are atypical or high grade tumors, their prognosis is generally inferior to other neuroendocrine tumors of similar stage and grade arising elsewhere in the body, particularly in the lung.
Given the rarity of these tumors, data to guide optimal treatment are limited by the small size of case reports and the lack of randomized prospective trials. There are no widely accepted guidelines for pretreatment evaluation and no evidence-based guidelines for post treatment surveillance. Further studies and case reports are needed to establish the same.
Nothing to Disclose: RKA, RK
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