内分泌療法中に小細胞癌に脱分化した前立腺癌の1例

Abstract

76歳男。患者は頻尿および排尿困難を主訴とした。前立腺生検を施行し, 低分化型前立腺癌およびGleason score 4+5の診断を得た。Maximum androgen blockade(MBA)療法を開始したところ, PSAは低下し, CT上でリンパ節腫脹の消失を認めた。しかし, その後, 腰背部痛が出現し, 疼痛による歩行困難, 嘔吐, 食事摂取困難が生じ緊急入院となった。所見ではFDG-PETで骨以外の病変として右肺尖部, S状結腸に集積を認め, 肺小細胞癌に準じた化学療法を考慮したが, 全身状態の不良にて施行できないまま急速に病状が悪化した。そして症状出現から約3ヵ月後に患者は死亡となった。尚, 剖検所見から本症例は低分化型前立腺癌が脱分化を来し, 多臓器に転移したものと考えられた。

A 76-year-old man had been treated with maximum androgen blockade therapy for a poorly-differentiated prostate adenocarcinoma (T3cN1M0, prostate specific antigen (PSA) 65 ng/ml, Gleason Score 4+5=9) since September 2002. By August 2003, his serum PSA levels were undetectable and the lymph node swelling had vanished. However, in December 2004, his serum PSA levels started rising gradually up to 0.66 ng/ml. Radiation therapy on the prostate was then performed (66 Gy). At that time, no metastasis was detected by computed tomography and bone scintigraphy. In August 2005, multiple bone metastases were detected. Immunohistochemical examination of a biopsy specimen from the bone lesion revealed a small cell carcinoma/neuroendocrine cell carcinoma. He died with undetectable PSA levels (less than 0.008 ng/ml) in December 2005. The autopsy showed multiple organ metastases including bone, liver, lungs and others. The immunohistochemical examination revealed pure small cell carcinoma in all metastatic lesions. A precise histological examination of the lungs using a 1 cm serial section could not reveal any tumors compatible with primary lung cancer. We concluded from the clinical history and autopsy findings that his initial poorly-differentiated adenocarcinoma of the prostate dedifferentiated into a pure small cell carcinoma with neuroendocrine differentiation.