FINAL DIAGNOSIS: YOLK SAC CARCINOMA ARISING IN A MATURE TERATOMA OF THE LIVER.
The term teratoma is derived from the Greek root "teratos" which means monster. This name is applied to neoplasms which are characterized by abnormal growth of a combination of tissues derived from ectodermal, mesodermal, and endodermal germ layers. This combination of tissues is unrelated to the organ in which the tumor is arising. Teratomas have been described in numerous anatomic sites. 1 Most commonly these tumors arise in the ovaries or in the sacrococcygeal region in children.1 Other less common anatomic locations include the testes, mediastinum, and central nervous system. Rare teratomas arising in the gastrointestinal tract, liver, nasal sinuses, uterus, cervix, and thyroid2 have been reported. The biologic behavior of these neoplasms is also highly variable, some being entirely benign and others undergoing aggressive malignant transformation. Several hypotheses concerning the pathogenesis of these lesions have been suggested. The most commonly espoused hypothesis is that these tumors arise from primordial germ cells and primitive somatic cells which proliferate in an abnormal fashion due to absence of the regulatory influence of unidentified organizers and inducers.1 The definitive pathogenesis of these neoplasms has yet to be elucidated.
Teratomas of the liver are rare neoplasms accounting for less than 1% of all teratomas. The tumors more commonly occur in pediatric patients but still only account for less than 1% of all liver neoplasms in pediatric patients.3 Of the 25 hepatic teratomas described in the literature, 4 only five occurred in adult patients. The majority of described cases were in female children under three years of age, most arising in the right lobe of the liver. Of these cases, only 4 cases had documented malignant degeneration. The reported malignancies arising in hepatic teratomas include squamous cell carcinoma,5 "malignancies of hepatic and mesodermal components",6 and malignant neural elements.7 The most common germ cell malignancy arising in teratomas overall is the endodermal sinus tumor or yolk sac tumor.8 The most common malignancies arising in mature teratomas of any site are squamous cell carcinoma and sarcoma. Rare cases of primary yolk sac tumor of the liver have been reported.9
The patient described herein represents a unique instance of a hepatic teratoma with a germ cell tumor component, specifically yolk sac carcinoma. On presentation, this patient's serum alpha fetoprotein was markedly elevated and a similar elevation of serum alpha fetoprotein has been described in another case of primary hepatic teratoma.7 Following resection of the tumor and chemotherapy, the serum alpha fetoprotein has decreased to 4 ng/mL (most recently) and is being used as a tumor marker to screen for tumor recurrence in this patient. At present the patient has no evidence of tumor.
Contributed by Christine C. Dorvault, MD and Ronald Jaffe, MD