A case of stromal sarcoma of the prostate with the incidental detection of prostate adenocarcinoma

Abstract

Prostate stromal sarcoma is very rare among patients with prostate cancer, accounting for <0.1 % of prostate malignancy. Here, we report a case of prostate stromal sarcoma combined with incidental adenocarcinoma with normal serum PSA after radical prostatectomy. This case is unique in that the occurrence of incidental adenocarcinoma might interfere with the postoperative follow-up and treatment. We can only draw from the experiences of case reports and retrospective analysis. This article describes a presentation of a rare tumor case and a review of the literature.

1 Introduction

Prostate sarcoma is an uncommon kind of prostate cancer, with the incidence of primary prostate sarcoma among all prostate cancer diagnoses being less than 0.1 %. Prostate sarcoma can manifest as different pathological types since it originates from nonepithelial mesenchymal tissues such as smooth muscle, blood vessels, and nerves. Prostate stromal tumors, which originate from the mesenchymal components of the prostate, were first classified by Gaudin in 1998. Prostate stromal sarcoma, which originates from mesenchymal components of the prostate, is extremely rare among prostate sarcomas, accounting for only 5.2 % in patients over 25 years of age. Fewer than 100 cases of primary prostate stromal sarcoma have been documented in the literature to date. Here, we report a case of primary prostate stromal sarcoma with primary prostate adenocarcinoma in a 50-year-old man presenting with normal PSA and a large prostate mass.

2 Case report

A 50-year-old asymptomatic man presented to the Affiliated Hospital of Qingdao University in October 2021 with a prostate mass detected at a health checkup. The preoperative serum tPSA was 2.32 ng/ml; f/t was 0.10. A rectal examination revealed a large, benign-feeling prostate mass. The MRI signal showed a long T1, a mixed T2, and hyperintensity on DWI ( Fig. 1 ). PET/CT did not detect any suspicious metastasis. After clinical confirmation of the sarcoma by prostate needle biopsy, the patient underwent laparoscopic radical prostatectomy. The size of the surgical specimen was 9.0∗8.0∗8.0 cm, and the size of the center mass was 9.0∗6.0∗6.0 cm with a large necrotic area ( Fig. 2 ). However, the patient did not consent to neoadjuvant or adjunctive treatment due to a fear of chemotherapy. PET/CT has advantages in differentiating the presence of distant metastases, but it is difficult to detect local recurrence due to the excretion of radiotracer in the urine. One year after the operation, we first conducted a chest and whole – abdomen CT examination, and the results showed no signs of recurrence. However, during the review at the 19th month after the operation, a pelvic mass with a diameter of about 9 cm was detected. Subsequently, the patient underwent a pelvic mass resection, and the post – operative pathology revealed metastatic prostate stromal sarcoma. Despite our recommendation for chemotherapy, the patient still refused to receive it after the operation. Later, widespread intra – abdominal tumor metastasis occurred at the 28th month after the operation, and the patient unfortunately passed away at the 34th month after the operation.

Postoperative pathology revealed that the tumor was a prostate stromal sarcoma. The tumor tissue configuration was monophasic and composed of sarcomatoid spindle cells, which were arranged in interlacing fascicle patterns, similar to fibrosarcoma. Tumor cells showed moderate to severe atypia, and large necrotic areas were present among the tumor tissue. Pathological nuclear division was also observed in the hotspot (>15/10HPF). Giant cell formation and heterologous differentiation were not detected in the tumor tissue. Immunohistochemistry of the prostate stromal sarcoma showed that the expressions of ki67 and cd34 were positive, while those of CK were negative ( Fig. 3 ). Prostate stromal sarcoma genetic testing showed CDK4, MDM2, GLI1, IFITM3, ATRX, FRS2, THAP2, and TMEM4 mutations, low TMB and MSI, and lower expression of PD-L1.

Moreover, a piece of prostate adenocarcinoma with a size of 0.3∗0.2 cm was detected in the normal prostate tissues around the stromal sarcoma by accident in wax from the specimen’s surgical margin. The Gleason score of the prostate adenocarcinoma was 3 + 4 = 7. Immunohistochemistry of the adenocarcinoma showed that the expression of P504S was positive, while those of P63 and HCK were negative.

We also detected the expressions of PSA, androgen receptor (AR), estrogen receptor (ER), and progesterone receptor (PR) in the tumor. The expressions of AR, ER, and PR was positive in the prostate stromal sarcoma, while that of PSA was negative. In addition, the expressions of PSA and AR were positive in the prostate adenocarcinoma, while those of ER and PR were negative ( Fig. 4 ).