Malignant phyllodes tumor of the prostate

Prostatic stromal proliferations: a review

Prostatic stromal proliferations account for the majority of benign tumour-like lesions in the prostate. The most common is nodular hyperplasia, seen in a majority of elderly men. Diagnostic difficulty is encountered with some variants, including stromal hyperplasia with atypia, characterised by degenerative changes of myofibroblasts. In contrast with benign stromal tumours, malignant stromal tumours of the prostate are rare, accounting for less than 0.1% of all prostatic malignancies. The most common are rhabdomyosarcoma (paediatric) and leiomyosarcoma (adults); others include phyllodes tumour and stromal sarcoma. Some authors lump malignant tumours with poor outcome (e.g., phyllodes tumour and stromal sarcoma) with benign stromal tumours (e.g., stromal hyperplasia with atypia, leiomyoma), considering them collectively to be of uncertain malignant potential, but this approach is discouraged. This review presents a contemporary approach to classification and diagnosis of prostatic stromal tumours.

Mesenchymal tumours of the bladder and prostate: an update

Mesenchymal tumours of the urinary bladder and prostate are infrequent neoplasms. The body of literature is growing with isolated case reports and short series, and the majority of cases are benign neoplasms. Other than stromal tumour of uncertain malignant potential and prostatic stromal sarcoma, both neoplasms derived from the specific prostatic stroma, the mesenchymal neoplasms in these locations are identical to their counterparts seen in other organs. However, the limited amount of tissue generated by biopsy and rarity of mesenchymal lesions in these sites create unique diagnostic difficulties, while correct classification of the neoplasm often bears significant impact on prognosis and therapeutic strategy. In this review we summarise the diagnostic features, focus on the differential diagnosis, and highlight the potential diagnostic pitfalls of mesenchymal tumours of the bladder and prostate.

Non-epithelial neoplasms of the prostate

Non-epithelial prostatic neoplasms are infrequent and cover a broad array of entities that include both benign and highly aggressive tumours. Because they are very infrequent, there is often limited understanding of them, and the recognition of these entities, when encountered, may pose a diagnostic challenge, owing to histological overlap between them or their rarity. Most lesions in this category are mesenchymal in origin, such as prostatic stromal tumours arising from specialized prostatic stroma, smooth muscle tumours, both benign and malignant, and solitary fibrous tumours. Less commonly occurring tumours include neural, germ cell and melanocytic tumours that may be derived from cells not normally present in the prostate. Some tumours have well-established extraprostatic counterparts and, when encountered, are more commonly extraprostatic/secondary in origin; these include gastrointestinal stromal tumours and most haematopoietic tumours. The majority of tumours are characterized by a spindle cell pattern with significant overlap in morphological features. In this setting, appropriate use of immunohistochemistry and molecular studies are often necessary for accurate diagnosis, prognosis, or prediction for therapy. This review addresses and updates the clinicopathological features of the entire spectrum of non-epithelial tumours with an approach to the histological diagnosis.

A large cystic phyllodes tumor of the prostate

We report a 65 year-old man with a large cystic phyllodes tumor of the prostate. The patient complained of abdominal discomfort and had a soft palpable mass. Computer tomography showed a solid and cystic mass in the pelvic fossa; the mass was adjacent only to the prostate. We excised the mass. Microscopic findings of the mass showed hyperplastic epithelium lined cysts with leaf-like intraluminal epithelia lined stromal projections, less than 2 mitotic counts/10 HPF, low-to-moderated cellularity, and mild-to-moderate cytoplasm atypia. The pathological findings were consistent with a phyllodes tumor of the prostate, a low-grade tumor. Twenty-eight months after the operation, the patient was well with no recurrence or metastases.

Nonepithelial Tumors and Tumor-Like Lesions of the Prostate Gland

Many significant benign and malignant nonepithelial tumors and stromal tumor-like lesions arise in the prostate gland. Although such lesions are rare, their recognition by the pathologist is essential because their treatment and prognosis are quite variable. In this review, lesions of the specialized prostatic stroma, that is, lesions that can be seen in the stroma of the prostate but not in that of other organs, except for the phyllodes type of lesions, are discussed. Benign and malignant lesions of the soft tissues that occur in the stroma of other organs and are seen with some frequency in the prostate are also discussed. Few of the rarer soft tissue lesions are mentioned. Lesions and tumors with melanocytic differentiation, hematopoietic derivation, and germ cell tumors are described. It is hoped that this review will serve as a useful reference when encountering some of these lesions, all of which are referenced to their original and subsequent reports. Some non-English language references are also cited to reflect the international recognition of these lesions or to give credit to the author who first described the entity.

Malignant phyllodes tumor of the prostate

We report the case of a 47-year-old male patient who suffered from a malignant phyllodes tumor of the prostate with invasion to the rectum and urinary bladder. The local recurrence at the left scrotum was identified 6 years after radical cystoprostatectomy. Another 2 years after radical orchiectomy showed no evidence of secondary local recurrence or distant metastasis. Histopathologically, both primary and recurrent tumors showed an admixture of stromal and glandular components. However, while extensive squamous metaplasia was identified in the primary tumor, the recurrent tumor had only focal and mild squamous metaplasia. No dependable prognostic factor has been found to date. Here, we describe the morphological features and immunohistochemical presentations of malignant phyllodes tumor of the prostate and review the literature.

Phyllodes tumor of the prostate: long-term followup study of 23 cases

PURPOSE

Phyllodes tumor of the prostate is a rare neoplasm of uncertain malignant potential. We studied a large series of phyllodes tumors to define the combination of histological features that are most useful for predicting patient outcome.

MATERIALS AND METHODS

A total of 23 cases were obtained from our collective files from 1973 to 2002, and numerous clinical and pathological features were evaluated. A review of the reported cases of phyllodes tumor of the prostate was done.

RESULTS

Patient age was 25 to 86 years (mean 55) and they usually presented with urinary obstructive symptoms and hematuria. The diagnosis was made in 18 tumors by transurethral resection, in 2 by enucleation, in 1 by tumor resection and in 2 by prostatectomy. We analyzed 5 histological features, including cellularity (scale of 1 to 3), cytologic atypia (scale of 1 to 3), the number of mitotic figures per 10 high power fields, the stroma-to-epithelium ratio (low or high) and necrosis (present or absent). This combination of features revealed that 14 cases were low grade phyllodes tumor, 7 were intermediate grade and 2 were high grade with the high grade cases characterized by increased cellularity, severe cytological atypia, more than 5 mitotic figures per 10 high power fields and a high stroma-to-epithelium ratio, indicating stromal overgrowth. Immunohistochemical studies of 8 tumors revealed consistent, intense cytoplasmic immunoreactivity in stromal cells for vimentin and actin, in luminal epithelial cells for prostate specific antigen, prostatic acid phosphatase and broad-spectrum keratin AE1/AE3, and in basal cells for high molecular weight keratin 34beta-E12. Recurrence was seen in 7 of 14 low grade tumors (50%) and in 1 patient low grade sarcoma emerged with subsequent distant metastases 14 years after initial diagnosis following 5 recurrences. Recurrence was seen in 6 of 7 intermediate grade tumors and low grade sarcoma emerged with subsequent abdominal wall metastases in 1 patient 11 years after initial diagnosis following 3 recurrences. The phyllodes tumor recurred in each patient with high grade tumors with a time to first recurrence of 6 and 0.2 years, respectively. Distant metastases developed in these 2 patients.

CONCLUSIONS

Histological grading of prostatic phyllodes tumors is predictive of short-term outcome based on the combination of stromal cellularity, cytological atypia, number of mitotic figures and the stroma-to-epithelium ratio. However, these tumors usually recur after transurethral prostatic resection and they are often locally aggressive with time. The emergence of overt sarcoma and metastatic disease is more frequent than previously recognized. Complete resection at initial diagnosis appears to be indicated.

Phyllodes tumor of the prostate: Recurrent obstructive symptom and stromal proliferative activity

We report the case of a 59-year-old man with a metachronous development of phyllodes tumor and adenocarcinoma of the prostate. He complained of urinary obstruction and transurethral resections of the prostate (TUR-P) had been performed six times in 10 years. Microscopic examination showed cystically dilated glands consisting of bizarre cells with pleomorphic, hyperchromatic nuclei in the stroma at the sixth TUR-P. Radical prostatectomy was performed against recurrences and adenocarcinoma was incidentally detected. Apparent up-regulation of proliferative nuclear antigens (PCNA), but not p53, was observed in the prostatectomy specimen by Western blotting. Active proliferation of stromal cells is considered to have caused the recurrent obstructive symptom.

Malignant phyllodes tumor of the prostate: retrospective review of specimens obtained by sequential transurethral resection

A case of malignant phyllodes tumor of the prostate in a 67-year-old man is reported. The patient was referred to a hospital for urinary retention. From material taken at three transurethral resections of the prostate (TURP), a histological diagnosis of benign prostatic hyperplasia was made. However, at the fourth TURP, phyllodes tumor was diagnosed due to the presence of elongated epithelial ducts and proliferating cellular stroma with mitosis and nuclear atypia. Two months later, total cystoprostatectomy was performed. Histologically, the tumor was composed of dysplastic stromal cells and irregularly elongated epithelial ducts. Five months later the patient developed multiple lung and pelvic lymph node metastases and died. This report documents progression to a higher histological grade of prostatic phyllodes tumor documented with sequential pathological findings obtained from four TURP and surgical specimens over about 3 years.