prostatic sarcomatoid carcinoma

Sarcomatoid carcinoma is a rare biphasic malignancy in the prostate. Only approximately 100 cases have been reported in the literature.

The two elements of sarcomatoid carcinoma are a malignant epithelial (carcinomatous) component and a malignant mesenchymal or mesenchymal-like (sarcomatous) component.

Sarcomatoid carcinoma may be either homologous, where the mesenchymal-like areas have the appearance of an undifferentiated sarcoma, or heterologous, where the sarcoma exhibits differentiation along the lines of specific mesenchymal cells, such as bone and cartilage.

Carcinosarcoma is a term that is synonymous with heterologous sarcomatoid carcinoma.

Other terms that are equivalent to sarcomatoid carcinoma include metaplastic carcinoma, spindle cell carcinoma, and malignant mixed mesodermal tumour.

Clinically, most patients are approximately 70 years of age (range 47–91 years), and present with urinary tract obstruction and symptoms of frequency, urgency, and nocturia. On digital rectal examination, the palpable prostate is often enlarged, nodular, and hard. An equal number of men have normal and elevated serum PSA levels.

It is of note that, in about half of all cases, the initial diagnosis was a usual acinar adenocarcinoma, followed by hormonal and/or radiation therapy, with a subsequent diagnosis of sarcomatoid carcinoma.

The time between the initial diagnosis of acinar adenocarcinoma and the diagnosis of sarcomatoid carcinoma varied from 0.5 to 16 years, with a mean of 7 years.50

Grossly, prostatic sarcomatoid carcinomas at pelvic exenteration, prostatectomy and autopsy are large (55–180 mm), grey–white to pink masses with haemorrhage, necrosis, and local extension into surrounding structures such as seminal vesicles and the rectal wall.

Microscopically, the carcinomatous and sarcomatous components are admixed, with blending of the two in some areas. The carcinomatous element is almost always glandular and acinar.

Six cases were ductal adenocarcinoma, 11 cases demonstrated squamous differentiation or adenosquamous carcinoma, three cases had small-cell carcinoma, and one case had urothelial and squamous components.

The adenocarcinoma is typically high-grade, with a mean Gleason score of 9, and a range of 7–10. In most cases, the adenocarcinoma component is a minor component, but it is dominant in one-third of cases.

The sarcomatoid component often exhibits large areas of undifferentiated spindled and pleomorphic cells arranged in sheets, pinwheels, or fascicles.

Osteosarcoma and chondrosarcoma are by far the most frequently identified heterologous elements. Areas of fibrosarcoma, leiomyosarcoma, angiosarcoma and rhabdomyosarcoma are rarely found.

Different types of sarcomatous tumour can be found together in the same case.

Cytologically, nuclear pleomorphism is moderate to marked, with numerous mitotic figures, including atypical ones, which are readily identified. Tumour giant cells, including osteoclast-like giant cells, can be seen.

Immunohistochemical stains and electron microscopy have demonstrated mesenchymal or epithelial differentiation in the sarcomatoid component.

Epithelial markers (CK, PSA, and PSAP) and muscle markers can be detected by immunohistochemistry in the malignant spindle cells.

Vimentin immunostains are uniformly positive, and S100 protein is consistently found in chondrosarcomatous regions. In one case, skeletal muscle and vascular differentiation was substantiated by positivity for myoglobin and Ulex europaeus I agglutinin, respectively.

The outcome of patients with prostatic sarcomatoid carcinoma is poor, with median survival of 3 years and 7-year survival of 14%.

The disease can be locally aggressive, with local recurrences and the formation of large pelvic masses.

Sites of metastasis include, in order of frequency, the lung, bone, lymph nodes, and brain, with rare cases of metastatic spread to the skin, liver, peritoneum, adrenal, pleura, and kidney.

Epithelial and/or mesenchymal components can be seen in metastatic deposits. Treatment has varied; non-surgical therapy is ineffective.

The histological pattern does not predict progression and survival.

References

 Histological variants of prostatic carcinoma and their significance. Humphrey PA. Histopathology. 2012 Jan;60(1):59-74. PMID: 22212078