Cystic trophoblastic tumour

Chemotherapy for non-seminomatous germ cell tumours of the testis may leave residual masses. On excision, these may consist of teratoma, necrosis and fibrosis, which require no further therapy and have an excellent prognosis. Residual seminoma, embryonal carcinoma, yolk sac tumour or choriocarcinoma has a worse prognosis and requires further chemotherapy. Cystic trophoblastic tumour is a form of residual trophoblastic tumour, but with a good prognosis.

Macroscopic appearances

The residual lesions are composed of multiple small with circumscribed borders. Most cases are multifocal.

Histopathology

The cysts are lined by trophoblastic cells, varying from one to several cells in thickness. The mitotic rate is low. These foci are set within a fibrotic background and are associated with mature teratoma. Haemorrhage is absent.

Immunohistochemistry

Rare cells were positive for hCG in 10 of 12 cases1.

Differential diagnosis

Choriocarcinoma forms larger masses (> 1 cm), which are nodular, with an infiltrating growth pattern. There is a biphasic pattern and mitoses are frequent. Haemorrhage and necrosis are usually present. hCG immunoreactivity is diffuse.
Teratoma shows differentiated somatic-type epithelium (squamous, goblet cell, ciliated or other specialized types). hCG is negative. The distinction of cystic trophoblastic tumour from mature teratoma does not seem to be clinically important.

Management

Further chemotherapy is not indicated.

Prognosis

Excellent.

References

1Ulbright, T. M., J. D. Henley, et al. (2004). "Cystic trophoblastic tumor: a nonaggressive lesion in postchemotherapy resections of patients with testicular germ cell tumors." Am J Surg Pathol 28(9): 1212-6.

This page last revised 31.10.2004.