Reported herein is an unusual case of prostatic
phyllodes tumor with exuberant glandular
hyperplasia that led to misdiagnosis of
adenocarcinoma. The
tumor was detected in a 52-year-old man who had a 1 year history of
dysuria.
Adenocarcinoma of the prostate was diagnosed from a needle biopsy specimen. The patient received hormonal
therapy for 6 months and underwent radical
prostatectomy. Histologically, the
tumor had an atypical stromal cell proliferation and elongated slit-like glands characteristic of a
phyllodes tumor. The
tumor was also accompanied by a florid proliferation of small acini, most of which lacked basal cells, a common manifestation of
adenocarcinoma in the overall
tumor area. The following features of the resected
tumor were helpful for concluding that these acini were benign: lack of cytological
anaplasia in spite of structural atypia, presence of scattered basal cells confirmed by immunohistochemistry (high-molecular-weight
cytokeratin), and histological transition from these acini to apparently benign slit-like glands. The final diagnosis was then made as '
phyllodes tumor of the prostate with exuberant glandular
hyperplasia'. Atypical stromal cells might provide a clue for the recognition of this rare
tumor at initial diagnosis by needle biopsy.