Ovarian tumors
GERM CELL TUMORS
Germ cell tumors constitute 15% to 20% of all ovarian tumors.
Most are benign cystic teratomas, but the remainder, which are found principally in children and young adults, have a higher incidence of malignant behavior and pose problems in histologic diagnosis and in therapy.
Teratomas
Teratomas are divided into three categories:
(1) mature (benign).
(2) immature (malignant).
(3) monodermal or highly specialized.
Mature (Benign) Teratomas
Most benign teratomas are cystic and are better known in clinical practice as dermoid cysts.
These neoplasms are derived from the ectodermal differentiation of totipotential cells.
Cystic teratomas are usually found in young women during the active reproductive years.
Morphology:
Benign teratomas are bilateral in 10% to 15% of cases.
Characteristically, they are unilocular cysts containing hair and cheesy sebaceous material.
On section, they reveal a thin wall lined by an opaque, gray-white, wrinkled, apparent epidermis.
This epidermis, hair shafts frequently protrude.
Within the wall, it is common to find tooth structures and areas of calcification.
About 1% of the dermoids undergo malignant transformation of any one of the component elements (e.g., thyroid carcinoma, melanoma, but most commonly, squamous cell carcinoma).
In rare instances, a teratoma is solid but is composed entirely of benign-looking heterogeneous collections of tissues and organized structures derived from all three germ layers.
These tumors have the same histogenetic origin as dermoid cysts but lack preponderant differentiation into ectodermal derivatives.
These neoplasms may be initially difficult to differentiate from the malignant, immature teratomas, which almost always are largely solid.
Pathogenesis of teratoma:
The karyotype of all benign ovarian teratomas is 46,XX. From the results of chromosome banding techniques and the distribution of electrophoretic variants of enzymes in the normal and teratoma cells, suggestive theory that these tumors arise from an ovum after the first meiotic division.
The ovarian carcinoid:
It presumably arises from intestinal epithelium in a teratoma, might in fact be functioning, particularly in large (greater than 7 cm) tumors, producing 5-hydroxytryptamine and the carcinoid syndrome.
Primary ovarian carcinoid can be distinguished from metastatic intestinal carcinoid, the latter virtually always bilateral.
Even more rare is the strumal carcinoid, a combination of struma ovarii and carcinoid in the same ovary.
Primary carcinoids are uncommonly (less than 2%) malignant.
Immature Malignant Teratomas.
These are rare tumors that differ from benign teratomas in that the component tissue resembles that observed in the fetus or embryo rather than in the adult. The tumor is found chiefly in prepubertal adolescents and young women, the mean age being 18 years.
Morphology
The tumors are bulky and have a smooth external surface. On section, they have a solid (or predominantly solid) structure. There are areas of necrosis and hemorrhage. Hair, grumous material, cartilage, bone, and calcification may be present.
Microscopic examination:
Tthere are varying amounts of immature tissue differentiating toward cartilage, glands, bone, muscle, nerve, and others.
An important risk for subsequent extraovarian spread is the histologic grade of tumor (I through III), which is based on the proportion of tissue (in histologic sections) containing immature neuroepithelium.
Immature teratomas grow rapidly and frequently penetrate the capsule with local spread or metastases.
Stage I tumors, however, particularly those with low-grade (grade 1) histology, have an excellent prognosis.
Higher-grade tumors confined to the ovary are generally treated with prophylactic chemotherapy.
Most recurrences develop in the first 2 years, and absence of disease beyond this period carries an excellent chance of cure.
Dysgerminoma
The dysgerminoma is best considered as the ovarian counterpart of the seminoma of the testis. Similar to the seminoma, it is composed of large vesicular cells having a clear cytoplasm, well-defined cell boundaries, and centrally placed regular nuclei. Relatively uncommon tumors, the dysgerminomas account for about 2% of all ovarian cancers yet form about half of malignant germ cell tumors. They may occur in childhood, but 75% occur in the second and third decades. Some occur in patients with gonadal dysgenesis, including pseudohermaphroditism. Most of these tumors have no endocrine function. A few produce elevated levels of chorionic gonadotropin and may have syncytiotrophoblastic giant cells on histologic examination.
Morphology
Usually unilateral (80% to 90%).
Size range from barely visible nodules to masses that virtually fill the entire abdomen.
On cut surface, they have a yellow-white to gray-pink appearance and are often soft and fleshy.
Microscopical examination:
The dysgerminoma cells are dispersed in sheets or cords separated by scant fibrous stroma.
As in the seminoma, the fibrous stroma is infiltrated with mature lymphocytes and occasional granulomas. On occasion, small nodules of dysgerminoma are encountered in the wall of an otherwise benign cystic teratoma.
predominantly dysgerminomatous tumor may contain a small cystic teratoma.
All dysgerminomas are malignant, but the degree of histologic atypia is variable, and only about one third are aggressive. Thus, a unilateral tumor that has not broken through the capsule and has not spread has an excellent prognosis (up to 96% cure rate) after simple salpingo-oophorectomy. These neoplasms are extremely radiosensitive, and even those that have extended beyond the ovary can generally be controlled by radiotherapy. Overall survival exceeds 80%.