Teratoma of the neck is uncommon location. Most of them present as midline involvement and they have relationship with thyroid gland[4]. Many congenital cervical teratoma can be mistaken as cystic hygroma[4]. We report a rare case of huge congenital mature cystic teratoma in an 8-month-old baby boy; it was located at the lateral neck and mimicked congenital cystic hygroma. Due to some uncommon histological findings, we reviewed the literature to classify and grade the tumour.
Figure 1: T2-weighted MRI demonstrating a mixed-intensity lesion with mainly fluid component.
On gross pathological examination, it was a cystic mass measuring 15x12x6 cm in diameter and 5-8 mm in wall thickness. It contained yellowish gelatinous material. Serial cut sections showed partly solid and partly cystic with variegated appearance. Solid areas measured about 3x4x3 cm in diameter (Figure 2).
Histopathologically, the cyst wall was partly lined by stratified squamous epithelium and partly by respiratory typed pseudostratified ciliated columner epithelium (Figure 3A). Subepithelial tissue showed many large foci of mature neuroglial tissue (Figure 3B). Other mature tissue components such as choroid plexus epithelium (Figure 3C), mucus secreting glands, pancreatic acini, salivary glands, adipose tissue, skeletal muscle, bony trabeculae and cartilages were seen in the cyst wall. Most of the solid area was composed of mature neuroglial tissue with astrocytes, oligodendrocytes and numerous psammomatous calcifications (Figure 4A). Foci of mature ependymal cells forming tubules and rosettes were also seen (Figure 4B). Some of the foci of cartilages showed immature cartilage without a clear cut margin which accounted for less than 10% of sample tissue (Figure 4C). However, immature neuroglial tissue components were not seen. Sections from one enlarged cervical lymph node showed foci of mature neroglial tissue within a lymphoid architecture. Based on the above histopathological features, the cystic mass was diagnosed as mature teratoma (Grade 1) and the cervical lymph node was diagnosed as nodal gliomatosis.
Approximately one third of the reported cervical teratomas complicate maternal hydramnios[12]. However, there was no maternal hydramnios in this case although the mother had history of gestational diabetes.
Pathologically, teratomas have heterogeneous histological characteristics. Mature teratomas may contain all manners of adult tissues with varying degrees of organoid development, whereas immature lesions may produce embryonic or extra embryonic fetal tissue[4]. Up to 90% of childhood teratomas contain derivatives from all three embryonic germ layers. 20–40% contain some immature tissues. In childhood, 75–85% of teratomas of the head and neck region usually contain neuroectodermal elements (both mature and immature)[6]. Mature neuroectodermal tissue such as cerebellum, ependymal tubules, pituitary and retina can be seen in mature teratoma and it does not result misclassification as an immature teratoma[13]. Ependymal rosettes should not be mistaken for the primitive rosettes seen in an immature teratoma. The cells lining ependymal rosettes have ample cytoplasm, the nuclei form only one or two layers, and mitotic figures are not present[14]. In this case, foci of ependymal cells forming tubules and vague rosettes were also seen.
Grading and classification of both gonadal and extragonadal teratomas are important for the management and sometimes challenging for the anatomic pathologist. Teratomas are generally classified into four grades according to the Gonzalez-Crussi grading system[4]. Grade (0): all component tissues appear well differentiated, grade (1): occasional microscopic foci contain incompletely differentiated tissues but not exceeding 10% of the sampled tissue, grade (2): Immature tissue composed of 10-50% of sampled tissue, and grade (3): more than 50% of sampled tissue are composed of undifferentiated tissue. Both grade (0) and (1) are considered as mature teratoma and both grade (2) and (3) are considered immature teratoma (4). Our case contained foci of incompletely differentiated immature cartilage which accounted less than 10% of all sampled tissue; we therefore decided the case was mature teratoma, grade (1). All teratomas that contain areas of germ cell tumour, non-germ cell malignant tumour and immature teratoma with metastasis are considered malignant teratoma (4). Most of the gynaecological literatures for ovarian teratoma put grade (1) teratoma under immature teratoma[15].
In this case, the striking feature was presence of large multiple foci of mature neuroglial tissue consisting of astrocytes, oligodendrocytes, neuron, microglia, ependymal cells and even multiple foci of psammomatous calcification. Most of the foci of glial tissue were hypercellular like a glial tumour. However, they did not exhibit any pleomorphism or mitosis. Foci of mature neuroglial tissue were also seen in section of cervical lymph node adjacent to the tumour that was diagnosed as nodal gliomatosis. Nodal gliomatosis is not indicative of malignant biological behavior and appears to have the same prognostic significance as gliomatosis peritonei in mature ovarian teratoma[16]. In this case, it is possible that previous sclerotherapy caused extraction of neuroglial tissue from cystic teratoma and implantation in the nearby cervical lymph node resulting in nodal gliomatosis.
In conclusion, most of the congenital head and neck teratomas are benign and mature in nature with a good prognosis. Teratoma should be in the list of differential diagnosis for congenital lesions presenting as a neck mass. An ample amount of neuroectodermal tissue including ependymal rosettes should not be mistaken as immature elements.
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