Dr. Sachin Almel discusses the case report, histologic presentation, and treatment approach for yolk sac tumour, a rare occurrence in adults beyond 30 years of age.

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Yolk sac tumour is a subtype of germ cell tumour that is highly malignant. In addition to presenting in ovaries and testes, the tumour has been detected at several extra-gonadal sites such as the retroperitoneum, sacro-coccygeal region, pineal gland, and the anterior mediastinum.

Case report

A 41-year-old male had complaints of dry cough for 3 months 2 years back, investigated at local area was found to have a 6.7*6.8*8.8 cm cyst in anterior mediastinum. He resorted to ayurvedic treatment for around a year. He presented to our institution with complaints of increasing severity in cough and weight loss of 5 kg in 3 months.

On examination, he was found to have reduced air entry in the whole left lung field. CT thorax was done which was suggestive of 12.7*14.8*15.6 cm anterior mediastinal mass partially encasing main pulmonary artery, indenting pericardium with pericardial effusion and multiple bilateral lung deposits with left sided pleural effusion. AFP was elevated to a value of >300000 IU/ml with normal beta-HCG. Biopsy of lesion was suggestive of yolk sac tumour.

Discussion

Extra gonadal germ cell tumours have been speculated to develop from primordial germ cell remnants that fail to migrate to gonadal ridge during embryogenesis. Hence, the locations of development of EGGCT fall along the migration pathway of the primordial germ cells to gonadal ridge. The mediastinum is the most common site of EGGCTs. Malignant GCT in the mediastinum accounts for 1–6% of all mediastinal tumours. Primary extra-gonadal GCTs, especially primary mediastinal tumours, are considered to have poor prognosis. GCTs are histologically categorised into teratomas, teratocarcinomas, seminomas, and nonseminomatous carcinoma, including choriocarcinoma, embryonal carcinoma, yolk sac carcinoma, and mixed type carcinoma. Greater than 90% of malignant extragonadal tumours of the mediastinum occur in men.

Yolk sac tumours (YSTs) can occur in both men and women, usually arising from germ cells in testes and ovaries, respectively. Pure YST tumours are usually found in young children and mixed germ cell tumours with YST are found in adults. Yolk sac tumours, similar to other nonseminomatous germ tumours, can be associated with haematologic Klinefelter’s syndrome (upto20%) and other haematological malignancies such as acute leukaemia and myelodysplastic syndrome.

Histologic presentation

Microcystic/reticular pattern is the most common histological presentation. Schiller-Duval bodies are pathognomonic and are helpful for identification. Yolk sac tumours immunohistochemical testing is positive for AFP,glypican-3,SALL4,and placental alkaline phosphatase.

Treatment

The treatment regimens of extragonadal and gonadal YSTs are similar since they share histological patterns. Extragonadal nonseminomatous germ cell tumours have considerably poorer prognosis.

1. Cisplatin based chemotherapeutic regimens have shown significant results with up to 50% of patients achieving long-term survival. Bleomycin, Etoposide, Cisplatin (BEP) therapy at least 4 cycles is a widely accepted chemotherapy regimen.
2. Surgical resection as the primary treatment modality is not recommended in mediastinal GCTs because of the likelihood of early metastasis. However, there is a definite role for post-chemotherapy adjuvant surgery to remove residual lesions and a rising serum tumour marker after completion of chemotherapy is not considered as a contraindication for surgery. Complete resolution of serum AFP marker occurs in less than 5% of patients. Survival rates have increased in patients who have decrease in serum of AFP after chemotherapy and in cases with residual tumour surgical excision.

Extragonadal and mediastinal GCTs are diseases of childhood or early adulthood. It rarely appears after the age of 30 years. Primary mediastinal yolk sac neoplasm is a rare tumour. High index of suspicion is needed to diagnose extragonadal GCTs in adult patients. Diagnosis can be made with elevated AFP in conjunction with a supporting histopathology.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

The author, Dr. Sachin Almel is a Consultant Medical Oncologist from Mumbai.