O-methylguanine-DNA methyltransferase immunoexpression in a double pituitary adenoma: case report.
OBJECTIVE
Double pituitary adenomas in surgical cases are rarely reported. The incidence in published surgical specimens ranges from 0.4% to 1.3%. We present a treatment dilemma of a double adenoma that had differential O-methylguanine-DNA methyltransferase (MGMT) reactivity.


METHODS
A 48-year-old man presented with acromegaly and a recurrent pituitary adenoma. He had elevated growth hormone (GH) and elevated insulin-like growth factor blood levels and hyperprolactinemia.


METHODS
Subtotal transsphenoidal resection was performed. Morphologic examination disclosed 2 histologically distinct tumors, including a GH adenoma and a prolactin adenoma. Immunohistochemistry revealed Ki-67 labeling indices of 1% and 2%, respectively. Of significant note was MGMT immunopositivity in the GH adenoma and lack of staining in the prolactin adenoma.


CONCLUSIONS
This is the first clinical instance in which MGMT was assessed in double adenomas of the pituitary. The 2 tumors showed significant differences in reactivity that could impact chemotherapeutic management. The adenomas underwent recurrence, a feature that reflects their invasive nature and the possibility that chemotherapeutic intervention may be required in the future. Response to temozolomide use is anticipated with respect to the prolactin adenoma but would likely not benefit the GH cell adenoma of our patient.
Mohammed
Safraz
S
Division of Neurosurgery, St. Michael's Hospital, and Department of Surgery, University of Toronto, Toronto, Canada. mohammedsaf@smh.toronto.on.ca
Cusimano
Michael D
MD
Scheithauer
Bernd W
BW
Rotondo
Fabio
F
Horvath
Eva
E
Kovacs
Kalman
K
D000236:Adenoma / Q000097:blood / Q000150:complications / Q000201:enzymology*; D015254:DNA Modification Methylases / Q000378:metabolism*; D045643:DNA Repair Enzymes / Q000378:metabolism*; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D006966:Hyperprolactinemia / Q000209:etiology; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000097:blood / Q000150:complications / Q000201:enzymology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D018969:Insulin-Like Growth Factor Binding Proteins; D019394:Ki-67 Antigen; D025521:Tumor Suppressor Proteins; D013006:Growth Hormone; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D045643:DNA Repair Enzymes