Congenital orbital teratoma up to posterior fossa.

Congenital orbital teratoma is a rare condition which presents as marked proptosis of eyeball in a newborn. It is rapidly progressive with secondary damage to eyeball due to pressure effect. This case presented by us is of interest due to radiological features and rarity of this tumor extending into posterior fossa.

Introduction

Congenital orbital teratoma is a rare condition which presents as marked proptosis of eyeball in a newborn. It is rapidly progressive with secondary damage to eyeball due to pressure effect. The tumor consists of encapsulated cyst with fluid and varied amount of solid tissue. Microscopically these tumors consist of well-differentiated tissues representing two or three germinal layers.[1]

Case Report

A 12-months-old child was brought to us with gradually progressive protruding mass in right orbital region since 8 months. Parents had noticed protrusion in right eye at the age of 4 months. Child was full-term normal home delivery. Child was born of a non-consanguineous marriage and there was no history of similar complaint in other sibling. On examination there was gross proptosis of right eyeball with everted palpebral conjunctiva and widened palpebral fissure. There was punctate bleeding from the exposed mucosa. There was no vision in right eye with exposure keratopathy.

X-ray skull, CT Brain with contrast, and MRI Brain with orbit was suggestive of enlargement of superior orbital fissure with erosion of superior orbital margin. MRI was suggestive of large heterogeneous mass containing both solid and cystic components extending through the enlarged superior orbital fissure along the lateral wall of cavernous sinus into middle cranial fossa and then into posterior fossa and compressing the brainstem [Figures 1 and 2]. It was pushing the eyeball downwards and outwards, with compression of the temporal lobe.

Figure 1

(a-c) MRI brain with orbit (with contrast) showing the lesion with extension up to posterior fossa. Tumor is extradural in location and compressing the brain stem

Figure 2

(a and b) Post operative CT scan brain with orbit (with contrast) residual part which was adherent to the brain stem

Patient was operated; initially exentration of eyeball by ophthalmologist followed with right pterional craniotomy and complete extradural approach, tracing the tumor from superior orbital fissure to posterior fossa along the lateral wall of cavernous sinus. Tumor consisted of multiple cystic spaces with few solid areas, cartilage, and muscle tissue [Figure 3]. Tumor was vascular. Part of tumor which was adherent to brain stem was left behind. Patient recovered well and was discharged. Patient is regularly following up with us.

Figure 3

(a-c) Histopathological slides showing all three germinal layers - endoderm (mucus glands), mesoderm (cartilage), and ectoderm (squamous epithelium)

Microscopically tumor showed components of all three germ layers. Numerous mucus glands were seen which is a endodermal component, catilagenous tissue was seen representing the mesodermal part and lining of squamous epithelium representing ectoderm. There was no evidence of malignant change on histology.

Discussion

The organiser theory (Spermann and Budde) modified by Krafka provides a more tenable explanation. This theory discusses interference with normal development of the growth center of the embryo allowing the development of secondary growth center. Migration of this center to different portions of the embryo leads to the occurrence of teratoma. The rare occurrence of orbital teratomas may be the result of the greater distance between the primordia of orbit and eye and primitive streak. Duke -Elder has classified teratomas of orbit as follows- 1. A complete fetus implanted in orbit (orbitopagus parasiticus), 2. A portion of second fetus in orbit, 3. a tumor consisting of all three germinal layers, 4. Tumors containing representative of two germinal layers only, 5. tumors containing representative of only one layer.[1]

In most teratomas, the ectodermal and mesodermal components predominate. Endodermal elements are frequently absent or difficult to detect. Jensen proposed that tumor containing all three germ layers should be called teratoma, with two germ layers should be called teratoid, and with single layer in orbit i.e. dermoid cyst are choriostomas. A review of literature showed, female preponderance, (2:1) and slight preponderance to left side. Only two cases were bilateral. Only two instance of malignant teratoma have been reported. Teratoma is considered malignant when the tissue is embryonic or immature in nature. Clinically, it is difficult to distinguish teratomas from other benign/malignant tumors. Differential diagnosis includes, dermoid cyst, micro-opthalamus with cyst, encephalocele, meningocele, neuroblastomas, neurofibroma, hemangioma, and lymphangiomas.[1]

The surgical treatment of these lesions almost always has been effective. These are direct orbital approach through the conjunctiva, intracranial approach, Kronlein operation, and exentration. Surgeons now recommend early surgery. Recurrence of continued growth of completely removed teratoma has been reported. Rapid enlargement of teratoma after birth is characteristic. The solid portions increase in size, and the amount of fluid increased. With expansion of mass, the eye becomes exposed, compressed, and eventually perforated.[12]

Conclusions

Our case presents a unique challenge as orbital teratoma extending to posterior fossa is extremely rare, not reported to the best of our knowledge. Interestingly a conservative approach in leaving behind part adherent to brainstem has helped in patient recovering well and as it is a benign tumor regrowth is still not seen on follow-up.