[Clinicopathological features of adenocarcinoma of the rete testis]

Objective: To investigate the clinicopathological features, immunophenotype, and differential diagnosis of adenocarcinoma of the rete testis. Methods: Four adenocarcinoma cases of the rete testis diagnosed at West China Hospital, Chengdu, China (3 cases, including 2 consultation cases) and the First Affiliated Hospital of Fujian Medical University, Fuzhou, China (1 case) between January 2009 and December 2017 were included. Their clinical, morphologic and immunohistochemical features were analyzed using histological analysis and immunohistochemical staining. Related literature was reviewed to reveal the characteristics of this tumor. Results: The 4 patients' age range was 26-64 years. The maximum diameters of the tumors were 3.0 and 4.5 cm in 2 cases, respectively. On gross examination, adenocarcinomas of the rete testis appeared as a solid, white to gray or tan to yellow mass that raised at the hilum of the testis. Microscopically, all tumors showed multiple histologic patterns, including corded/trabecular (4/4), glandular, nested, sarcomatoid (3/4), solid (2/4), papillary, cribriform, and slit-like (1/4). Three types of adenocarcinoma cells included cuboidal to columnar (4/4), polygonal (4/4) and spindle-shaped (2/4) with pale eosinophilic and clear cytoplasm. The tumor cell nuclei appeared moderately to markedly atypical and pleomorphic, with a various number of mitoses. Transition from benign to malignant rete epithelium was seen in all cases. Eosinophilic hyaloid globules were found in 1 case. On immunohistochemical study, the tumor cells were diffusely, strongly positive for CKpan (4/4), EMA (4/4), Ber-EP4 (3/3) and CAⅨ(2/2), and focally positive for CK7 (4/4), vimentin (4/4), CD10 (4/4), PAX8 (3/3), PAX2 (3/3). The Ki-67 proliferative index was all>50% (4/4). The prognosis was poor. Two of the 3 patients died within 1 year after the surgical resection. Conclusions: Adenocarcinoma of the rete testis is a rare malignant tumor with several histologic patterns. Transition from benign to malignant rete epithelium is an important diagnostic clue. Detailed clinical history, tumor growth site and immunohistochemistry are helpful for its diagnosis and differential diagnosis.