Primary Borderline Mucinous Testicular Tumor: A Case Report and Literature Review

Abstract

Primary mucinous tumors of the testis and paratestis are very rare, with only 29 reported cases detected in a PubMed search. The histopathological characteristics of primary testicular mucinous tumors are similar to their ovarian counterparts, and the diagnosis and naming criteria refer to the criteria for female ovarian mucinous tumors. However, the clinical and imaging features of primary testicular mucinous tumors are poorly understood, and they are thus frequently undiagnosed or misdiagnosed. We present the case of a patient with a primary testicular mucinous tumor. A 52-year-old man presented with a 1-year history of painless enlargement of the left scrotum. Ultrasound examination revealed a cystic mass in the left testis, with viscous fluid areas and calcified spots, irregular solid bulges on the cyst wall, and a small blood supply. Serum alpha-fetoprotein, β-human chorionic gonadotropin, lactate dehydrogenase, renal function, inflammatory markers, and routine urine and blood examinations were all normal. The patient underwent radical resection of the left testis. Postoperative pathology showed a multilocular cystic mass, with the inner wall of the sac lined with mucous columnar epithelial cells, some with mild nuclear atypia, and no interstitial infiltration. The pathological diagnosis was testicular mucinous tumor. Postoperative abdominal and pelvic computed tomography, colonoscopy, and gastroscopy showed no suspicious lesions. The final diagnosis was primary testicular borderline mucinous tumor. The patient underwent postoperative follow-up examinations once a year for 4 years. Serum tumor markers, scrotal ultrasound, abdominal and pelvic computed tomography scans, and colonoscopy and gastroscopy revealed no evidence of metastases or other primary adenocarcinoma. This case highlights the clinical and imaging characteristics of primary testicular mucinous tumors, which might aid their differential diagnosis.

Keywords: clinical characteristic; differential diagnosis; imaging characteristic; mucinous tumor; testis.

Figure 1

(A) Ultrasound examination of the scrotum revealed a mainly cystic, heterogeneous echogenic mass occupying most of the left testicle. The tumor had a clear boundary, regular morphology, and disordered internal echo. (B, C) Viscous fluid was seen in the cystic part, and large calcified spots were detected in some areas. (D) A few irregular solid protrusions were visible on the cyst wall with a small blood supply.

Figure 2

(A) Gross pathology showed that the multilocular cystic mass in the left testis occupied almost the entire testicular parenchyma (volume about 4.5×3.5×2.5 cm) with irregular thickening of the cyst wall and filled with gray-yellow jelly. (B) Microscopic pathology (hematoxylin and eosin staining ×200) showed that the inner wall of the capsule was lined with a single layer of pseudo-stratified mucus columnar epithelial cells, some showing mild nuclear atypia, but with no interstitial infiltration. (C) Microscopic pathology (hematoxylin and eosin staining ×20) also showed fibrous tissue proliferation of the cyst wall and mucus overflow into the cyst wall in some areas.

Figure 3

The ages of the 29 previously reported patients ranged from 11–78 years. They included 10 cases of borderline mucinous tumors and eight of mucinous cystadenocarcinoma, all in patients above 40 years old. Mucinous cystadenoma occurred in seven patients older than 40 years old and in five younger than 40 years old. Primary mucinous testicular tumors accounted for 83% (24/29) of patients above 40 years old, compared with 33% (8/24) of patients with mucinous cystadenocarcinoma. mucinous cystadenoma, borderline mucinous tumor, and mucinous cystadenocarcinoma.