Metastatic germ cell tumors in serous cavities and cerebrospinal fluid: A single-center experience.

Background: Metastatic germ cell tumors (GCTs) involving body cavity effusions and cerebrospinal fluid (CSF) are rare. Diagnosis is challenging because of limited morphological and clinicopathological information in the literature.

Methods: A database search of our institution from 1990 to 2024 identified 27 cases of metastatic GCTs, comprising five pediatric and 22 adolescent and adult patients, in serous cavities or the CSF, including peritoneal (15), pleural (nine), CSF (two), and pericardial (one) fluid.

Results: The most common primary site was the testis (n = 10), followed by the ovaries (n = 7), mediastinum (n = 4), retroperitoneum (n = 3), pineal gland (n = 2), and sacrum/coccyx (n = 1). The primary tumors in 14 patients were mixed GCTs (six with a seminoma component), followed by immature teratomas (six), yolk sac tumors (three), embryonal carcinomas (two), pure seminomas (one), and postpubertal teratomas (one). The median interval between primary tumor diagnosis and diagnosis of fluid positivity was 7 months (range: 0-134 months). In nine cases, the malignant fluid was diagnosed simultaneously with or within 1 month of the primary tumor. GCT subtyping was performed on 23 of the 27 cytological specimens. Twenty-four patients (89%) also had metastases to other sites. Thirteen patients died of the disease (48%), with a median survival time of 4 months.

Conclusions: Metastatic GCTs in serous effusions and CSF are often associated with disseminated disease and poor prognosis. Subtyping can be performed by cytomorphology combined with immunohistochemistry.