Extragonadal germ cell tumors (EGCT) account for 10% to 15% of all primary mediastinal tumors. Approximately 12% of mediastinal EGCT are yolk sac tumors (YST). We report a case of mediastinal YST that was initially misdiagnosed as non-small cell lung carcinoma (NSCLC), with detrimental consequences.
45-year-old male smoker was diagnosed, by CT-guided fine needle aspiration (FNA), to have NSCLC invading the mediastinum. He was transferred to our institution for further management two weeks later. Within 24 hours of admission, he developed septic shock requiring mechanical ventilation, vasopressors and broad-spectrum antibiotics. CT scan of chest revealed a mass in the right upper lobe invading the mediastinum and encasing the superior vena cava (SVC). The patient developed SVC syndrome and an SVC stent was placed. Due to the rapid progression of the tumor, a repeat CT-guided FNA was performed on day 9 of admission. Repeat scrotal examination was normal, and alpha-fetoprotein and beta-HCG levels were sent. The patient went into cardiac arrest the next day and ACLS protocols were unsuccessful. The initial pathology report of the repeat FNA was undifferentiated NSCLC. However, additional immunohistochemical stains were performed postmortem when his alpha-fetoprotein level was reported as 24,305ng/ml. The tumor cells were found to express cytokeratin, alpha-fetoprotein and placental alkaline phosphatase, but were negative for CK7, CK20, TTF-1, CD30, EMA and beta-HCG. This immunohistochemical profile is consistent with yolk sac tumor.
Probably, the first report of a mediastinal YST was by Teilmann in 1967. With a few exceptions, mediastinal YST appears to be restricted to males and usually presents in the second or third decades of life. At the time of diagnosis, almost 90% of the patients are symptomatic. The common symptoms include chest pain, shortness of breath, weight loss, chills and fever, and SVC syndrome. Over 85% of patients have extension of the tumor outside the mediastinum at diagnosis. Conditions associated with YST include Klinefelter’s syndrome and hematologic malignancies. The presence of the latter generally indicates a worse prognosis. The diagnosis of EGCT should be considered in young males who present with a mediastinal mass and have elevated levels of alpha-fetoprotein or beta-HCG. The histology of mediastinal YST displays the same wide spectrum of patterns as seen in the gonads, with the reticular pattern being the most common. Immunohistochemical staining helps differentiate YST from other germ cell tumors. YST usually stains positive for cytokeratin and alpha-fetoprotein, negative for Ki-1 and beta-HCG, and may be positive or negative for placental alkaline phosphatase. Mistaking mediastinal EGCT for undifferentiated NSCLC has been reported previously1. In this patient, the initial erroneous diagnosis was, in part, due to the small yield from the initial FNA resulting in inability to run the usual immunohistochemical markers for NSCLC. In the past, long-term survival was rare in patients with nonseminomatous EGCT. Incorporation of cisplatin-based chemotherapy has improved survival in these patients, with reported remission rates of 40% to 50% in most series, usually irrespective of histologic subtypes. Patients with residual mediastinal mass but normal serum tumor markers require complete surgical resection. Recurrent disease does not respond well to salvage chemotherapy.
When faced with a rapidly progressing mediastinal mass, a high degree of suspicion is necessary so as not to miss the diagnosis of EGCT. These tumors carry a better prognosis with chemotherapy than advanced NSCLC, emphasizing the importance of making this distinction. Our case highlights the difficulties that may be encountered in establishing the correct diagnosis.
Salim Harianawala, None.