Abstract
We report a case of a 66-year-old woman with a malignant transformation of a growth
hormone (GH)-producing pituitary adenoma that was mainly located in the clivus. The
patient originally presented with left oculomotor and abducens nerve palsies. Magnetic
resonance imaging revealed a clival tumor separated from the normal pituitary gland,
and the patient subsequently underwent transsphenoidal surgery. Analysis of the resected
clival tissue revealed proliferation of tumor cells with slightly irregular nuclei
but no mitosis. Although the Ki-67 labeling index was as high as 8.7%, p53 was negative.
Histologic analysis confirmed the diagnosis of a GH-producing pituitary adenoma. Two
months after the first operation, the tumor acutely enlarged and caused a subarachnoid
hemorrhage. Pathologic findings of the second surgical specimen showed significant
nuclear atypia. The Ki-67 labeling index increased to 27.7% and the p53 was positive;
there was no GH immunoreactivity. Following the second surgical intervention, the
patient was diagnosed with an atypical pituitary adenoma and underwent postoperative
local radiotherapy (50 Gy in 25 fractions). Twenty months after the first surgery,
multiple bone metastases were detected that led to the diagnosis of pituitary carcinoma.
This is the first report of a clival pituitary adenoma undergoing malignant transformation.
Because neuroimaging may underestimate local invasiveness in ectopic pituitary tumors,
it is essential to conduct a histologic examination to evaluate it. Further analysis
of similar cases is necessary to improve clinical management for this confused diagnostic
criterion.
Keywords
ectopic pituitary adenoma - clivus - malignant transformation - pituitary carcinoma
