Implantation, endometrium of the uterus.
After an ovum has been successfully fertilized by a spermatozoan in the ampulla of the oviduct, the
undergoes mitotic cell division (
) and becomes a multicellular structure called the
. The morula develops into the
, which is transported into the uterus. The process of the
attaching to the endometrium of the uterus is called
. Implantation occurs at the end of the secretory phase; the endometrium during this period of time is also called the
(days 25–28). Implantation usually occurs on the posterior wall of the body of the uterus. If implanta-
tion succeeds, the trophoblast differentiates into two cell layers: an inner
and an outer
attaches to and invades the endometrium of the uterus, and the process of placentation begins.
secreted by the placenta stimulates the
to remain active and continue to secrete
pregnancy. The photomicrograph on the
shows an implantation site enclosed within the connective tissue of the endometrium.
is the most common form of endometrial
cancer, accounting for approximately 80% of cases. The majority of cases
of endometrial adenocarcinoma arise in the setting of elevated levels of
unopposed by the action of
. Some cases, however, arise in postmenopausal women with
atrophy of the endometrium. Excess or unopposed estrogen may be due
chronic anovulation, obesity, ovarian granulosa cell tumors, or exogenous
hormone intake. In the early stage, the cancer is usually asymptomatic.
Common symptoms include vaginal bleeding,
and lower abdominal pain. Histologically, the cancer is characterized by
the presence of cells resembling the glandular cells of the endometrium,
and range from well differentiated with gland formation to poorly differ-
entiated with solid sheets of
. Endometrial biopsy is widely
used in the diagnosis of the cancer. Treatment options include surgical
removal of the uterus, radiation therapy, and chemotherapy.
, is a benign neoplasm, derived from smooth
muscle cells of the uterine myometrium. Leiomyomas represent the most
common benign neoplasm in women, and occur more frequently in
Americans. Leiomyomas occur in the reproductive years when estrogen levels
are high, and tend to regress during menopause. Most patients with F broids
are asymptomatic, but, as the tumor enlarges, symptoms may include abnor-
mal bleeding, menorrhagia, lower abdominal pain, and increased urinary
frequency. Grossly, leiomyomas are well circumscribed and may be in sub-
serosal, intramural, or submucosal locations. Leiomyomas can be single but
are often multiple and may become quite large. The cut surface is typically
white to tan, with a whorled, bulging appearance. Histologically, the tumor
cells appear as well- differentiated, spindle-shaped smooth muscle cells, often
with increased extracellular matrix, such as
. Leiomyomas rarely become their malignant counterpart,
, which usually develop
. Treatment options include
(removal of the F broid), and hormone therapy.