neonatal teratoma

Definition: Teratomas are neoplasms comprised of mixed elements derived from the three germ cell layers.

A teratoma is generally defined as a tumor arising from pluripotent cells, and it is precisely the heterogeneity of tissues present in such a tumor that best characterizes it; it is also commonly accepted that a teratoma must contain derivatives of more than one blastodermic layer, according
to traditional concepts of embryonic ontogenesis.

An important characteristic of teratomas of the newborn is their surprising capacity to form structures that "simulate" or reproduce organ development, as observed in the embryo and fetus. In general, this ability correlates with the degree of differentiation of the teratoma, and the resulting tissues are called "organoid" structures.

There is virtually no tissue in the body that cannot find its simile in teratomas: pancreatic acini, myocardium, endocrine tissues, glia, neurones,
skin, bowel, and others have been identified in teratomas at one time or another. Even the ocular lens is a structure reported to occur, though rarely, in teratomas.

The capacity for differentiation of teratoma cells is so great that it is rash to state that one or other type of tissue "is never found" these tumors. Whenever such a statement has been made, subsequent reports have disproved the validity of this generalization.

Teratomas, unlike. most human neoplasms, are classified into benign, malignant, and immature. They are, by definition, composed of a wide variety of tissues haphazardly arranged, usually representing derivatives of the three germ layers (although this is not indispensable for diagnosis), and of a nature that is alien to the site where they originate.

Immature teratomas may be defined as teratomas composed of tissues whose maturity lags behind vvith respect to the tissues of the host.

Thus, restricted foci of neuroblasts are not unusual in the periventricular region of ’the brain in a newborn, and may be expected in a teratoma of a neonate, but would be discrepant in a child several years old.

In general, a large amount of immature tissues bespealcs potential aggressiveness, although this statement must be qualified according to the site of ongin and other clinical characteristics of the neoplasm.

The caveat must be reiterated that in discussing germ cell tuners of infancy it is difficult to generalize; cases must be evaluated individually.

For instance, testicular teratomas in infants and young children may contain abundant immature sornatic tissues, but no case has been known to pursue an aggressive, metastasizing course in the absence of germ cell malignant tumor as part of the teratoma.

Nonetheless, varions histologie grading systems have been developed that use the amount of immature tissues present in a teratoma as a criterion to gauge prognosis; this approach has been validated by experience.

Teratorna was the most frequent tumor at the Children’s Hospital of Los Angeles (UCSF), with 40 examples among 110 neonatal tumors.

Of all teratomas, sacrococcygeal tumors are the most prevalent in newborns. Since the advent of ultrasonography, diagnosis is frequently made prenatally.

With modern imaging techniques, complications such as severe dystocia caused by the teratoma, nonimmunological fetal hydrops, polyhydramnios, or bleeding of the tumor from tears during parturition are preventable.

The affected infant is female in over three-quarters of the cases, and the tumor is, in most cases, unaccompanied by any other life-threatening anomalies.

Surgical correction is therefore the dominating concern, and this should be undertaken as soon as possible.

In the present state of surgical and medical advance, it is often possible and important to excise the tumor completely, even when massive, on the first day of life.

The chances for malignancy to manifest in the tumor are greater the longer it is allowed to remain in the patient.

Up to the fourth month of lift, most teratomas are benign and composed of mature tissues, but the majority of those removed in older children, especially over 2 years of age, are rnalignant.

It is not well understood why this should be the case, since malignancy probably does not develop de novo in a preexistent tumor. It may be that primitive germ cells remain dormant for a time but embark on a differentiation pathway of germ cell malignancy if the tumor remains undisturbed in its host.

In most cases, when the teratoma is malignant it owes its malignant character to tissue having the morphology of a yolk sac carcinoma or endodermal sinus tumor.

Accordingly, the detection of alpha-fetoprotein in the serum of these patients is a useful clinical tool. This type of malignancy is observed generally in teratomas of childhood.

Rarely do the malignant tissues of a teratoma adopt a different form. On occasion, probably no more than in 2% of teratomas, it is the immature neuroectodermal component that behaves aggressively, including the development of metastases.

The rarity with which this occurs justifies a cautiously conservative attitude vis-à-vis the teratomas that contain no germ cell malignancy; however, teratomas that contain a very large amount (half or more of the total bulk of the tumor) of prirnitive neuroectodermal tissue should be viewed as potentially-malignant.

In our experience, widely metastasizing neuroectodermal tissue in teratomas often contains tubular structures reminiscent of the primitive embryonic neural tube. The tubular histological appearance often rnisleads the pathologist into diagnosing "adenocarcinomas" of various histogeneses, an error that may be avoided today by performing immunohistological procedures that reveal the presence of neural antigens.

Localization

Teratomas occur in various sites of the body, generally along the midiine; the biology of this tumor seems to depend to some extent on the anatomical location in which they arise and on the age of the patient.

 Sacrococcygeal teratoma - A sacrococcygeal teratoma appears typically as a mass attahed by a broad pedicle to the sacrococcygeal region of term infants, predominantly of the female sex. It may also be hidden in the hollow of the sacrum, retroperitoneally.

As all teratomas, it may be cystic or solid. The majority are benign, but tend to recur when they are not surgically excised "en bloc" with the coccyx.

Occasionally, a sacrococcygeal teratoma that was diagnosed as benign after thorough sampling of the resected primary may recur as an undifferentiated tumor. Although the reasonable assumption that in such cases a focus of malignancy went undetected, the true explanation is not always clear.

Regardless of the cause, a practical corollary is that oncofetal markets of high sensidvity,such as alpha-fetoprotein, should be investigated in the serum of patients with teratornas, regardless of their histologic appearance.

A persistent rise after surgery is prima facie evidence of recurrence, and a stronger indication of the probable malignancy of the tumor than the histologic assessment of the primary.

Testis - Teratomas of the testis in infants have a good prognosis. We know of no well—authenticated case of a testicular teratoma with metastases at presentation in individuels’ below the age of 4 years.

This is in striking contrast to testicular teratomas of adolescents or yourg adults. Testicular teratomas of young children or infants appear to be composed of somatic tissues of varions degrees of differentiation and maturation, but usually do not contain arecs of germ cell malignancy. Teratomas of the testis in older patients may barber zones of embryonal carcinoma or variants thereof.

Endodermal sinus tumors may be present in the testis of young children, but usually not in the infantile period, and when present they manifest in a "pure" form, that is, without any other histological pattern being present. This is in contrast to adult patients, in whom endodermal sinus tumors rarely occur by themselves, and are usually seen in combination with other histological types of tumor, such as teratomas, embryonal carcinomas, choriocarcinomas, or seminomas.

 Other sites - Other sites at which teratomas may be observed in newborns and young infants include the mediastinum, central nervous system, retroperitoneum, neck, palace and oropharynx, kidney, orbit, and stomach.

The prognosis of teratomas of these anatomical sites is related to the critical regions which they arise. For instance, mediastinal teratomas produce compression of cardiovascular structures, and intracranial teratomas may be fatal by disturbing central nervous system structures. It is rare, however, that teratomas of these locations contain tissues capable of distant spread.

See also

 mature teratoma

• ovarian dermoid cysts
   immature teratoma

According to age

 fetal teratoma
 neonatal teratoma