Purpose or Case Report: Germ cell tumors of childhood are most often gonadal in origin. Extragonadal germ cell tumors are located characteristically in the midline arising intracranially, in the mediastinum, pelvis or retroperitoneum. These tumors are generally easily diagnosed due to typical sites of origin and characteristic imaging findings.

However, germ cell tumors can be associated with unusual clinical syndromes or imaging features that can perplex the clinician/radiologist.

We will review and illustrate atypical imaging/clinical manifestations and complications of germ cell tumors in childhood, based on our experience at two large children’s hospitals.

These atypical findings include:
Atypical metastatic disease: a) Burned out tumor – Testicular primary not typically evident with viable metastatic disease in retroperitoneal lymph nodes distant viscera, b) Growing teratoma syndrome (increasing size of tumor/pseudoprogression despite appropriate therapy), c) gliomatosis peritonei (maturation into glial tissue during therapy with pseudoprogression on FDG-PET), d) ossified pulmonary metastasis mimicking granulomas

Antibody mediated paraneoplastic syndromes: a) anti–N-methyl-D-aspartate (NMDA)– receptor antibody–mediated encephalitis associated with ovarian teratomas, b) anti-Ma2 antibody-mediated encephalitis associated with testicular germ cell tumors
Endocrine manifestations: a) Precocious puberty/gynecomastia due to hormonal (hCG) production, b) hyperthyroidism (TSH stimulation and struma ovarii)

Local complications: a) ovarian torsion (common), b) ruptured teratoma or dermoid cyst (uncommon)

Unusual primary tumors: a) Multifocal primary (e.g. pineal and suprasellar germinoma), b) Currarino triad, c) fetus-in-fetu, d) malignant transformation
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