Case of the Month

Discussion

Most cystic teratomas of the mediastinum represent true neoplasms as opposed to developmental malformations.  Teratomas are classically defined as neoplasms that contain at least two tissue derivatives from the three developmental germ layers (ectoderm, mesoderm, and endoderm).

Teratomas constitute anywhere from 10-20% mediastinal neoplasms (LeRoux et al, 1984; Mullen and Richardson, 1985), and the majority are confined to the anterior compartment of the mediastinum. Cystic teratomas of the mediastinum are largely tumors of children and young adults with an average age of 20 years at presentation (Karl and Dunn, 1985). Approximately half of affected patients display no symptoms with the other half displaying vague chest symptoms such as increased coughing or chest pain (Dehner 1990). A minority of teratomas of the mediastinum are associated with Klinefelter’s syndrome, but the incidence between sexes remains roughly equal (Nicholas et al, 1987).

Several radiological and gross factors are associated with the clinical behavior of mediastinal teratomas. Internal septations and calcifications are indicators of a more benign clinical course (Wu et al, 2002). Grossly, tumors that are adherent to the lungs, pericardium, or blood vessels almost invariably behave in a malignant fashion (Dehner 1990). Mucoid cysts, keratinaceous debris, and apparent osteocartilagenous foci are conversely associated with a benign clinical course.

The varying tissue types in teratomas is quite diverse and can also include choroid plexus, hepatocytic islands, pancreas, and pigmented neuroepithelium resembling retina (observed in this case, Figure 4), have all been reported in teratomas.

Grading of teratomas relies solely on the presence of immature neural tissue. Although immature tissue from mesodermal or endodermal tissues may be present, only the presence of immature neural elements correlates with a worse clinical course. “Mature” teratomas contain no foci of immature neural tissue at low power magnification. Grade 2 “immature” teratomas contain less than four foci of immature neural tissue at low power magnification (observed in this case). Grade 3 “immature” teratomas contain four or greater foci of immature neural tissue at lower power magnification.

Sources Cited

Dehner LP. Germ cell tumors of the mediastinum. Semin Diagn Pathol1990;7:266–284.

Karl SR, Dunn J. Posterior mediastinal teratomas. J Pediatr Surg 1985;20:508–510.

LeRoux BT, Kallichurum S, Shama DM. Mediastinal cysts and tumors. Curr Probl Surg 1984;21:1–77.

Mullen B, Richardson JD. Primary anterior mediastinal tumors in children and adults. Ann Thorac Surg 1986;42:338–345.

Nichols CR, Heerema NA, Palmer C, et al. Klinefelter’s syndrome associated with mediastinal germ cell neoplasms. J Clin Oncol 1987;5:266–284.

Wu TT, Wang HC, Chang YC, et al. Mature mediastinal teratoma: sonographic imaging patterns and pathologic correlation. J Ultrasound Med 2002;21:759–765.