A large soft tissue mass with multiple cysts—Primary leiomyosarcoma of the seminal vesicle

Abstract

To our knowledge, less than 20 cases are reported in the literature. Since many of these sarcomas are large and extensively infiltrative, definitive evidence of the seminal vesicle as the tissue of origin is often lacking. The preoperative assessment showed that the patient was in good general condition without obvious signs of metastasis, and the patient underwent total tumor resection, cystoprostatectomy and pelvic lymph node dissection. Primary leiomyosarcoma of the seminal vesicle is reported to have a poor prognosis. Because the seminal vesicle is closely related to the prostate and bladder, it is difficult to avoid local invasion of malignant tumors such as sarcoma, so an enlarged surgery is necessary.

Dear Editor,

Primary leiomyosarcoma of the seminal vesicle is exceedingly rare. To our knowledge, less than 20 cases are reported in the literature. Since many of these sarcomas are large and extensively infiltrative, definitive evidence of the seminal vesicle as the tissue of origin is often lacking. In recent years, the accuracy of preoperative diagnosis has been greatly improved with the wide application of magnetic resonance (MR), especially the MR multidirectional imaging.

A 79‐year‐old man with a history of suprapubic discomfort and dysuria with occasional pain during defecation for 3 months was admitted to urinary clinic. On routine rectal examination, a huge prerectal mass was palpated in the middle of the pelvis. Physical examination revealed no other additional symptoms.

Abdominal computed tomography demonstrated a polycystic, large and irregular mass in the pelvic cavity and focal high density (Figure A, white arrows) could be found inside the lesion, indicating hemorrhage. The following abdominal MR scanning showed that the cystic‐solid mass was located between bladder and rectum (Figure B) and there was no apparent boundary to the prostate and bladder. Patchy hypointensity on T2‐weighted images (Figure B) and hyperintensity T1‐weighted images (Figure C, white arrowheads) was found in the mass, which indicates hemorrhage. Coronal T1 late postcontrast phase showed obvious and progressive enhancement of the internal septa in the mass (Figure D, arrows). In our opinion, this mass might originate from seminal vesicle. Multiple cystic changes within the lesion were considered to be seminal vesicle dilations caused by tumor invasion, and a part of the cysts showed hyperintensity on T1‐weighted images, which suggested possible hemorrhage. Microscopic evaluation of the tumor revealed leiomyosarcoma (Figure E). The preoperative assessment showed that the patient was in good general condition without obvious signs of metastasis, and the patient underwent total tumor resection, cystoprostatectomy and pelvic lymph node dissection. Immunohistochemistry stains revealed CD117 negativity and smooth muscle actin positivity confirming leiomyosarcoma (Figure F).

A, Computed tomography of the pelvis showed a huge soft tissue mass with multiple cysts arising from the seminal vesicle and there was some hemorrhage (white arrows) inside the lesion. B, Transverse T2‐weighted magnetic resonance image of pelvis showed a large tumor between bladder and rectum. C and D, Coronal T1 precontrast imaging (C) showed short T1 signal which indicated hemorrhage (white arrowheads). Coronal T1 late postcontrast phase (D) showed obvious and progressive enhancement of the internal septa (white arrows), the margins adherenting to the prostate were indistinct. E, Histopathological findings showed moderate to high atypia in the irregular fascicles of the spindle cells, the tumor cells were arranged in a braid‐shaped pattern with a distinct nucleus (HE staining; ×400 magnification). F, Immunohistochemically, these tumor cells were positive for alpha‐smooth muscle actin (SMA) (×400 magnification)

Primary leiomyosarcoma of the seminal vesicle is extremely rare and highly malignant with an overall misdiagnosis. The incidence of leiomyosarcoma in the seminal vesicles is far lower than in the uterus, although they all originate from ductus mesonephricus, which may be associated with androgens. As the origin of pelvic tumors is difficult to determine, it is often easy to cause the removal of the dispensable organs. Radiological imaging can determine the origin of the tumor by clearly showing the relationship with neighboring structures through multidimensional imaging. In this case, MR helped us to detect that there was no lymphadenopathy and pelvic bone metastasis. The main differential diagnosis of primary leiomyosarcoma of the seminal vesicle was huge neurilemmoma in pelvic cavity. Neurilemmoma also appeared as cystic solid tumors, while they mostly contain punctate calcification and less bleeding, which were the main points of differentiation.

Primary leiomyosarcoma of the seminal vesicle is reported to have a poor prognosis. Because the seminal vesicle is closely related to the prostate and bladder, it is difficult to avoid local invasion of malignant tumors such as sarcoma, so an enlarged surgery is necessary. We believe that the treatment of choice is radical surgical excision of the tumor with complete removal of the lesion and cystoprostatectomy with pelvic lymphadenectomy. It is suggested that adjuvant radiotherapy should be considered when the boundary between the tumor and adjacent structures is not clear, but the effect is uncertain. Postoperative chemotherapy should be valuated case by case, the gemcitabine‐docetaxel combination is likely efficient.

CONFLICTS OF INTEREST

All authors declare no conflicts of interests.

STATEMENT

The study was approved by the ethics committee of WeiHai Central Hospital in 8 July 2018 and written informed consent to publish the material was obtained from the patient.