GCTs may occur in gonadal or extragonadal sites. In children younger than 15 years, the most common primary sites of GCT are the ovary (26%), coccyx (24%), testis (18%) and brain (18%).[5
] Extragonadal teratoma is the most common congenital tumor[6
] and, in infancy, sacrococcygeal tumors predominate, other extragonadal sites being mediastinum (4%), retroperitoneum (4%) and vagina (2%).[6
] Extragonadal GCTs are rare and constitute only 1–5% of all GCTs.[3
] Mediastinal GCTs presenting during childhood are extremely rare[7
] and immature teratomas are the rarest, accounting for only about 1% of mediastinal teratomas.[8
] Anterior mediastinum is the more common site and posterior mediastinal teratomas are occasional, with 18 cases reported till 2000.[9
Extragonadal GCTs usually arise as a result of aberrant migration of the progenitor germ cell.[10
] In spite of a common origin, these tumors demonstrate diverse clinical, radiological, morphological and histological variations. Of the 15 cases included in this review, six have presented with features not commonly associated with GCTs, some not reported in the published English literature.
Neuropsychiatric paraneoplastic syndromes have been described with virtually all tumors, but most commonly with small cell lung cancers.[11
] Such syndromes are usually due to immune-mediated encephalitis[11
] and are occasionally seen with gonadal GCTs, but are unusual in extragonadal GCTs. The details regarding the initial presentation of Case no. 1 have been previously reported elsewhere.[14
] Most of the patients who have developed immune-mediated encephalitis in conjunction with GCTs have demonstrated resolution of neurological symptoms either with tumor extirpation or with immunosuppressive therapy.[11
] It is interesting that these symptoms did not reappear with the histologically similar recurrence years thereafter.
The most common extragonadal GCT in young children is a sacrococcygeal tumor. These tumors are seen in conjunction with low-anorectal malformations as part of the Currarino triad, which always comprises a certain degree of sacral hypoplasia.[15
] One study has included a few children in this syndrome despite the presence of a normal sacrum because they had a HLXB9 mutation characteristic of Currarino's syndrome. A high-anorectal malformation is unusual in children with sacrococcygeal teratoma (Case 13) with or without Currarino's syndrome.[16
The radiological characteristics of GCT are generally predictable; these tumors appear as complex masses with solid and cystic areas with variable amounts of fat, fluid and calcification. The presence of fat–fluid levels has been said to be highly specific for teratomas.[20
] The presentation as a predominantly thin-walled large cyst with nonenhancing walls, few incomplete thin septae and containing clear fluid (Case 7) is unusual. This tumor had a very small solid component with minimal calcification that was overlooked and a strong possibility of a retroperitoneal lymphatic cyst was entertained preoperatively. Intraoperative aspiration of the cyst yielded a clear watery fluid that further strengthened the possibility of lymphatic cyst.
Tumoral calcification in GCT may resemble bone formation, more commonly in benign (up to 76%) than in malignant teratomas (up to 25%).[22
] Toothlike calcification or rim calcification is seen in approximately 56% of GCT.[23
] Recognisable teeth may be present in up to 29% of benign ovarian teratomas.[24
] Although tooth-like differentiation is common, osseous organoid differentiation as in Case 2 is only sporadically reported.[25
Teratomas are tumors composed of a variety of cell types derived from more than one germ layer; they can occur in any region of the body, commonly in the paraxial and midline location.[26
] They are thought to arise from totipotent cells that differentiate along various tissue lines such as skin, muscle, fat, cartilage, etc. These structures are usually admixed haphazardly and rarely form well-defined gross anatomical structures such as the colonic wall seen in one of our cases (Case 8). Mature teratomas behave in a benign fashion in contrast to immature teratomas, which may be clinically malignant in behavior. Histologically, the latter contain “immature” elements, such as immature neuroepithelium or immature mesenchymal tissue. Rarely, immature metanephric elements such as glomeruli-like structures[27
] may also be seen as in two cases in this series (Cases 8 and 10). The risk of recurrence can be estimated from parameters such as primary site of tumor, histological grade of immaturity and completeness of tumor excision. Malignant GCT s (teratomas, yolk sac tumors, embryonal carcinomas and dysgerminomas) are characterized by an infiltrative growth pattern and lymphogenous/hematogenous spread.[5
] They account for 2.9% of all malignant tumors of children younger than 15 years of age, and more than half occur at extragonadal sites.[5
] Two of our cases (Cases 2 and 11) showed yolk sac tumors, one of these (Case 2) in association with teratomatous elements (malignant mixed germ cell tumor).
El Kalla et al
., reported a case of benign posterior mediastinal teratoma infiltrating the lower third of the esophagus. This was a dumbbell like extension of a posterior mediastinal teratoma protruding through the esophageal hiatus.[28
] In Case 5, the infiltration of the immature teratoma was limited to the serosa microscopically. However, on gross examination, the gastroesophageal junction was encased by the tumor and the surgeons felt it necessary to resect it with the tumour to achieve complete excision.
Mature teratomas have been reported to demonstrate a high degree of differentiation often resembling tissues of normal organs. Instances of a mature cystic teratoma of the ovary associated with a complete colonic wall[29
] and colonic type adenocarcinoma arising in a primary retroperitoneal mature cystic teratoma[30
] have been reported in adults. Well differentiated colonic mucosa has been observed in an infant with sacrococcygeal teratoma and associated anorectal malformation;[16
] another sporadic report details the presence of colonic loops in a mature teratoma.[31
] Yet, it is not very common for these tumours to demonstrate organoid development; in Case 8, the immature retroperitoneal teratoma harbored a colonic wall in entirety. The mucosa, muscularis mucosa, submucosa, both layers of muscularis propria and both submucosal and myenteric plexii with clusters of ganglion cells were clearly identifiable.
Complete surgical excision is effective for children with immature teratomas with/without malignant elements (POG/CCG intergroup study),[26
] and salvage chemotherapy has been successful in those with recurrent disease. Except one (Case 1), all cases of immature teratomas in this series have undergone only complete surgical excision and have not recurred. Case 1 was an immature teratoma (Norris Gr 2) who presented with a recurrence 7.5 years after initial surgical excision; the recurrence was histologically similar to the primary tumor. It is unclear why this tumor behaved differently from other immature teratomas. Considering the aggressive tumor behavior, he received platinum-based chemotherapy after the excision of the recurrence.