石灰化を伴ったpleomorphic TSH-producing pituitary adenomaの1例

A Case of Pleomorphic TSH-producing Pituitary Adenoma with Calcification

　Ⅰ．はじめに

TSH産生腺腫は下垂体腫瘍の0.5～2.8％^4,7,12,13)を占める稀なホルモン産生腺腫で，組織学的には多角形や短紡錘形の腫瘍細胞がびまん性に増殖し，腫瘍間質に線維増生をみることがあるが，石灰化を伴った症例は現在までにわずかに6例^{1,3,15,16,21)}の報告があるにすぎない．

　最近，著しいpleomorphismを呈した石灰化TSH産生下垂体腺腫の1例を経験したので，病理所見を中心に文献的考察を加えて報告する．

　We reported a rare case of pleomorphic TSH-producing pituitary adenoma with calcification and reviewed the literature.

　A 25-year-old female was admitted to our hospital with a complaint of anterior neck swelling. An endocrinological examination demonstrated elevated serum levels of free triiodothyronine (FT3 : 5.6 pg/ml),free thyroxin (FT4 : 2.2 ng/dl),TSH (5.85 mIU/ml),and TSH a-subunit (5.9 ng/ml),whereas a physical examination revealed no goiter. CT scan showed a suprasellar isodensity mass with dense calcification. Contrast-enhanced T1-weighted images revealed a less enhancing tumor extending from the left upper portion of pituitary fossa into suprasellar cistern. The patient underwent gross total removal of the tumor via the right pterional approach. Microscopically,medium-sized to enlarged tumor cells with marked pleomorphism and prominent calcification were observed.The tumor cells displayed positive reaction for TSH (β-subunit). The MIB-1 index averaged 2.9%. The histological diagnosis was a pleomorphic TSH-producing pituitary adenoma. Postoperatively,the serum levels of FT3,FT4,TSH,and TSH α-subunit decreased to normal range. Follow-up MR images showed no evidence of recurrent tumor 3 years after the resection. All of six patients with densely calcified TSH-producing pituitary adenoma,previously reported in the literature,remained well without tumor recurrence. We suggest that this type of TSH-producing pituitary adenoma may be associated with favorable prognosis despite histologically pleomorphic appearance.