Session: MON 167-198-Hypothalamus-Pituitary Development & Biology
Poster Board MON-170
Irida Balili, Paul Mckeever, Ariel Barkan
Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan 48109, USA
Background. Pituitary carcinoma is characterized by the presence of a metastatic lesion(s) in a location non-contiguous with the original pituitary tumor. The mechanism(s) of malignant transformation are not known.
Clinical case: A 15 year-old man was diagnosed in 1982 with a pituitary macroadenoma and acromegaly (random GH 67 ng/ml and no suppression by oral glucose). His prolactin was normal between 18-23 ng/ml.
Transcranial resection in July 1983 was followed by radiation therapy. Histological examination showed a mosaic of cells positive predominantly for GH and prolactin. The proliferation MIB-1 index was 0-1%. With aqueous Octreotide 100 mcg 4x daily his mean GH declined from 19.1 ng/ml to 2.4 ng/ml (by RIA) and IGF-1 normalized from 510 to 112 ng/ml ( nl< 284). The patient was lost to follow-up and was treated by his local physician.
In 2001, he came back to our clinic: his IGF-1 levels increased up to 1271 ng/ml, and his random GH was 1.8 -2.4 ng/ml by ILMA despite progressive increase in the dose of Sandostatin LAR to 140 mg/month in divided doses. Prolactin remained normal between 15-25 ng/ml.
In 2009 he developed left hearing loss and disequilibrium and was diagnosed with the tumor in the location of left endolymphatic sac. Histological examination of the excised tumor showed low grade epithelioid neoplasm without the histologic features of endolymphatic sac tumor. Immunohistochemical stains were strongly positive for prolactin but negative for GH. MIB-1 antibody labeled 0-5% cells. Given the history of pituitary neoplasm and the location of this lesion, a diagnosis of well-differentiated lactotroph pituitary carcinoma was made.
In 2012, due to failure of pharmacological therapy, endoscopic resection of the pituitary tumor remnant was attempted. Immunohistochemical stains were strongly positive for both prolactin and GH, similar to his original pituitary tumor. The MIB-1 proliferation index was low from 0-1%.
Conclusion: To our knowledge this is the first case of pituitary carcinoma in the endolymphatic sac region. The dichotomy between the cell population of the pituitary lesion (GH/prolactin producing) and the metastasis (purely prolactin-producing) is intriguing. It may suggest that the metastatic pituitary lesions may derive from a clone distinct from the original one. The development of somatostatin unresponsiveness and metastatic potential may implicate radiotherapy as a causative factor of malignant transformation.
Nothing to Disclose: IB, PM, ALB
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