Prostatic duct adenocarcinoma with pagetoid spread on the glans penis: a case report

75歳男。71歳時に多発性膀胱癌にて根治的膀胱全摘除術を施行され、この際前立腺から偶発癌を認めた。LH-RHアナログを術後10ヵ月目まで使用し、以後は再発、転移なく経過していたが、今回、亀頭に自覚症状を伴わない紅斑局面が出現した。病理組織所見で表皮内にPaget細胞を認め、乳房外Paget病と診断された。陰茎全摘除術を施行し、摘除標本の病理組織所見でPaget細胞は亀頭から尿道内へも連続し、尿道舟状窩まで存在し、更に尿道粘膜下の導管内に乳頭状に増殖する腫瘍細胞を認めた。この腫瘍細胞は尿道切除断端まで連続して存在し、以前の前立腺摘出標本にも切除断端遠位端の尿道周囲導管内に辺縁域の腺房型腺癌とは異なり乳頭状に増殖する腫瘍細胞を認めた。免疫組織化学染色ではPaget細胞がcytokeratin 20に陽性を示したためPaget現象と診断した。Androgen receptor染色は前立腺導管内の腫瘍細胞、尿道粘膜下導管内の腫瘍細胞共に陽性、PSA染色は前立腺導管内の腫瘍細胞は陽性、尿道粘膜下導管内の腫瘍細胞は陰性を示した。PSAの染色性は異なるが、Androgen receptorの染色性と組織像の類似性、連続性から、前立腺導管癌が尿道粘膜下を進展し亀頭にPaget現象を呈したものと診断された。術後9ヵ月経過現在、再発転移は認めない。
A 75-year-old male visited our division with asymptomatic erythema on the glans penis which he first noticed six months earlier. The patient underwent total cystoprostatectomy under the diagnosis of urothelial carcinoma of the urinary bladder four years earlier. At the time, the prostatectomy specimen incidentally revealed a prostatic acinar adenocarcinoma at the bilateral peripheral zone. A skin biopsy of the erythema revealed intraepithelial Paget's cells, and the patient underwent total penectomy under the diagnosis of extramammary Paget's disease. Histopathological examination revealed continuous intraepithelial Paget's cells from the glans penis to the urethral navicular fossa, and a ductal carcinoma was detected beneath the urethral mucosa to the excisional margin. Because the Paget's cells expressed cytokeratin 20, the tumor was diagnosed as Pagetoid spread rather than Paget's disease. Re-examination of the previous prostatectomy specimen revealed prostatic duct adenocarcinoma with prostatic acinar adenocarcinoma. Therefore, the final diagnosis was prostatic duct adenocarcinoma with Pagetoid spread to the glans penis. Follow up at nine months revealed neither local recurrence, nor distant metastases, although no adjuvant therapy has been given.