Female genital tract

Female sexual development

Female development does not require the presence of a gonad, and the ovary plays no part in primary sexual development. This means that a neuter embryo will always develop along female lines. The testis-determining factor is the SRY gene carried in the sex-determining region of the Y chromosome. The indifferent gonad develops into an ovary when no Y chromosome is present, although two functional X chromosomes are usually required for normal ovarian differentiation. Disorders of female sexual development are listed in Table 19.1 .

Embryological development

Germ cells arise in the wall of the yolk sac, and migrate to the region of the coelomic germinal epithelium. In the sixth week, cords of cells appear within the indifferent gonad, but it is not until after the seventh week that ovarian differentiation is apparent and by 14 weeks these cell cords surround the primordial follicles.

The paired paramesonephric Müllerian ducts arise as an invagination of the coelomic epithelium of the mesonephric ridge lateral to the mesonephric duct. The paramesonephric duct follows the mesonephric duct. Near the cloaca, the paramesonephric ducts cross from the lateral to the medial side of the mesonephric ducts ( Fig. 19.1A ); together they carry with them some mesoderm from the side walls of the pelvis to create the transverse bar which helps to form the septum dividing the rectum from the urogenital sinus.

At the 30 mm stage (8 weeks), fusion of the paramesonephric ducts creates the uterovaginal canal, which ultimately forms the uterus and proximal part of the vagina ( Fig. 19.1B ); the unfused parts form the uterine tubes. The transpelvic bar, which is a continuation of the mesonephric mesentery, forms the broad ligament; the ovary, projecting medially from the mesonephric ridge in the early stage, comes to lie posterior to the broad ligament. The inferior free end of the fused paramesonephric ducts (uterovaginal canal) is still solid, and the sinovaginal bulbs grow out from the posterior wall of the urogenital sinus to fuse with it and, later, give rise to the lower part of the vagina. The hymen occupies the position where the sinovaginal bulb and urogenital sinus meet. The gonads are at first elongated and lie in the long axis of the embryo. Later, each gonad assumes a transverse lie. The gubernaculum is formed in the inguinal fold as a fibromuscular band which burrows from the gonad to gain attachment to the genital swelling; thus the caudal pole of the gonad becomes relatively fixed. The gubernaculum persists as the round ligament of the uterus. The ovaries retain attachment to the posterior aspect of the broad ligament. The genital swellings form the labia majora, the genital folds form the labia minora, and the genital tubercle forms the clitoris.

Herpes virus infection

Sexually transmitted herpes virus infection is usually due to herpes simplex type 2, and produces painful ulceration of the vulval skin. Histologically, intraepithelial blisters are seen with disruption of surface squamous epithelium, accompanied by specific cytopathic effects characterised by intranuclear viral inclusions and eosinophilic cytoplasmic swelling.

Candidiasis

Candida may cause chronic irritation and inflammation of the vulva that may be associated with vaginitis. The diagnosis may be made by microscopic examination of skin scrapings or culture. The histological features are nonspecific, although the fungi may be identified within the keratin layer or superficial epithelium with the use of special stains.

Cysts and tumours

Any benign cyst or tumour of the skin may be seen in the vulva.

Bartholin glands

Bartholin glands are common sites of cysts and of abscesses secondary to infection of a cyst. Bartholin gland adenoma is uncommon, and adenocarcinoma arising at this site is rare.

Intraepithelial neoplasia

The term VIN refers to the spectrum of preinvasive neoplastic changes affecting the vulva. In its classical form, it is the same as that of lesions in the cervix, although it may be incorrect to draw too close an analogy with the cervix as far as natural history is concerned. It is a condition that predominantly affects young women, and is associated with high-risk human papillomavirus (HPV) infection (see below). In severe cases, there may be extensive involvement of the perineum, including the perianal area. The incidence of malignant change occurring in these lesions is low compared with that for the cervix. There is a tendency for intraepithelial neoplasia to occur multifocally, with synchronous or metachronous involvement of vulva, vagina and cervix. Another type of VIN is the differentiated form which occurs in elderly women and is usually associated with lichen sclerosus.

Squamous carcinoma

Squamous carcinoma ( Fig. 19.3 ) is a tumour predominantly affecting elderly women in whom it is usually associated with differentiated VIN and lichen sclerosus but not HPV infection. The appearances are those of squamous carcinoma in any site; thus the tumour may be well, moderately or poorly differentiated. The prognosis is determined by the size, depth of invasion and degree of histological differentiation of the tumour, and the presence and extent of lymph node metastases, which predominantly affect the inguinal lymph nodes.

In contrast to squamous carcinoma of the cervix, even minimally invasive disease in the vulva is associated with a risk of local lymph node metastasis, although this risk seems to be negligible for carcinoma invading to a depth of less than 1 mm. Tumour thickness greater than 5 mm and positive lymph nodes are associated with a poor prognosis.

Paget disease

The rare occurrence of mucin-containing adenocarcinoma cells within the squamous epithelium of the vulva is analogous to Paget disease of the breast ( Ch. 18 ). Paget disease of the vulva tends to be chronic, with multiple recurrences. It may be indicative of an underlying invasive adenocarcinoma (in about 25% of cases), usually of skin adnexal origin, although, unlike the equivalent breast lesion, this is not usual. Adenocarcinomatous differentiation within the squamous epithelium has also been proposed as a possible explanation.

Other malignant tumours

Other malignant tumours of the vulva are rare. The most important of these are basal cell carcinoma , for which local excision is usually curative, and malignant melanoma , which, as in other sites, generally has a poor prognosis.

Infections

Vaginal infections are common and often sexually transmitted. The organisms of most importance are Gardnerella vaginalis , Neisseria gonorrhoeae , Candida albicans and Trichomonas vaginalis .

Vaginal adenosis

The occurrence of glands within the subepithelial connective tissue of the vagina is uncommon, and is believed to be due to a defect in embryological development. The lining of these glands is usually a mucinous cuboidal epithelium which may undergo squamous metaplasia. Clear cell adenocarcinoma of the vagina may rarely complicate adenosis.

Vaginal squamous neoplasia

Vaginal intraepithelial neoplasia is much less common than cervical intraepithelial neoplasia (CIN) but the same diagnostic criteria are applied. The lesion may coexist with similar lesions of the vulva and cervix (reflecting the multicentric origin of squamous neoplasia). Vaginal squamous carcinoma is an uncommon tumour predominantly occurring in older women. Pathologically, the tumour resembles squamous carcinoma of the cervix but it has a propensity to local invasion, and radical surgery may be necessary.

Cervicitis

Nonspecific acute and/or chronic inflammation is common in the cervix, particularly in the presence of an intrauterine contraceptive device, ectopy (see below) or prolapse.

Chlamydiae are obligate intracellular organisms containing DNA and RNA, and are larger than viruses. Chlamydia trachomatis is a common sexually transmitted infection which is often recognised by its persistence following treatment for gonorrhoea in males (postgonococcal urethritis). Chlamydiae can be isolated from the cervices of about 50% of asymptomatic female partners of these infected males and from women with chronic cervicitis. Chlamydial infection may produce subepithelial reactive lymphoid follicles, a condition sometimes given the label of ‘follicular cervicitis’.

Cervical polyps

Benign polyps of the cervix are common. They are composed of columnar mucus-secreting epithelium and oedematous stroma. Vessels may be prominent and there may be acute or chronic inflammation of varying severity. These polyps have no malignant potential.

Cervical microglandular hyperplasia

Cervical microglandular hyperplasia is a commonly seen complex glandular proliferation that may be confused with carcinoma. Small, tightly packed glands, lined by low columnar or cuboidal epithelium, may form polypoid projections into the endocervical canal. Accompanying acute inflammation and reserve cell hyperplasia (see below) are often seen. These changes may be seen in pregnancy and in users of the oral contraceptive pill, where they are the result of high levels of progestogen. Microglandular hyperplasia may also rarely be seen in postmenopausal women. It appears to have no malignant potential.

Aetiology

Squamous neoplasia of the cervix is associated with sexual activity; early age at first intercourse, frequency of intercourse and number of sexual partners are all risk factors. The sexual behaviour of the male partner is probably also of importance. There is probably no one single cause of cervical cancer or precancer, but epidemiological evidence points to a sexually transmitted agent or agents. There is now compelling evidence that HPVs are implicated in the aetiology of cervical squamous neoplasia. Cigarette smoking is an independent risk factor; some contents of cigarette smoke, which can be detected in cervical mucus, may act as cocarcinogenic agents. The polycyclic aromatic hydrocarbons in cigarette smoke form damaging adducts with DNA; these have been demonstrated in cervical tissue at higher levels in current smokers.

Human papillomaviruses and neoplasia of the lower female genital tract

Genital warts or condylomata have been recognised for centuries. Only comparatively recently, however, has their viral aetiology been established. Electron microscopy showed the presence of viral particles, and immunohistochemistry (using antibodies to viral capsid antigen) and in situ hybridisation (using DNA probes) also confirmed their viral nature. Warts may affect the vulva but may also involve the cervix ( Fig. 19.4 ). Moreover, it is now appreciated that HPVs may infect the vulva, vagina and cervix in a noncondylomatous manner. Such infections show characteristic morphological features; most important of these is a specific cytoplasmic vacuolation called koilocytosis ( Fig. 19.5 ). The features associated with HPV infection are:

• koilocytosis

• hyperkeratosis

• parakeratosis

• papillomatosis

• individual cell keratinisation (dyskeratosis)

• multinucleation.

These morphological features are also common accompaniments of vulval, vaginal and CIN. There are now more than 100 subtypes of HPV recognised and certain of these show a particular predilection for the lower female genital tract, notably HPV 6, 11, 16 and 18. HPV 6 and 11 are found in benign condylomata and are only rarely implicated in malignant transformation. HPV 16 and, to a lesser extent, 18 are found in CIN and in nearly 100% of cervical carcinomas. Other types, such as HPV 31 and 33, have also been reported in carcinoma. These are the oncogenic HPV types.

Papillomavirus DNA may be present either extrachromosomally (episomal) or integrated into the host DNA. Integration of the viral genome into host DNA is usual in high-grade CIN (see below) and invasive cervical squamous carcinoma. The protein coding sequences of the viral early (E) or late (L) open reading frames appear to have a major role in oncogenesis. Most interestingly, the E6 protein of HPV type 16 is capable of binding to the cellular p53 protein to form a complex that neutralises the normal response of cervical epithelial cells to DNA damage (apoptosis mediated by p53), which may thereby allow the accumulation of genetic abnormalities. E6 protein of low-risk HPV types (e.g. 6 and 11) does not appear to form a complex with p53. Thus unlike many other solid tumours, mutation of the p53 gene is an uncommon event in cervical carcinogenesis, as there is an alternative mechanism for its inactivation.

The protein p16 is a cyclin-dependent kinase inhibitor that phosphorylates the retinoblastoma protein (pRb). HPV 16 and 18 E7 proteins have the ability to bind to pRb, thus affecting its tumour suppressor role; this leads to overexpression of p16 which can now be demonstrated immunohistochemically and used as a surrogate marker of high-risk HPV infection.

HPV vaccination has been implemented in many countries. The vaccine comprises virus-like particles produced by recombinant DNA technology.

Physiological and neoplastic changes in the cervical transformation zone

Before puberty, the squamocolumnar junction lies within the endocervical canal ( Fig. 19.6 ). With the onset of puberty and in pregnancy, there is eversion of the columnar epithelium of the endocervix so that the squamocolumnar junction comes to lie beyond and on the vaginal aspect of the external os. This produces the clinical appearance of a cervical ‘erosion’, an unfortunate term, as the change is physiological. The term ectopy is more appropriate. The columnar epithelium is then exposed to the low pH of the vaginal mucus and undergoes squamous metaplasia. This is a physiological phenomenon, and takes place through the stages of reserve cell hyperplasia and immature squamous metaplasia. Reserve cells undermine the columnar mucus-secreting cells and multiply. This labile epithelium is called the transformation zone and is the predominant site for the development of cervical neoplasia.

CIN refers to the spectrum of epithelial changes that take place in squamous epithelium as the precursors of invasive squamous carcinoma. The severity of the lesion is assessed subjectively as grade (CIN) 1 (low grade), 2 or 3 (high grade), according to the level in the epithelium at which cytoplasmic maturation is taking place ( Fig. 19.7 ). Abnormal nuclei are present throughout the thickness of the epithelium, and mitotic figures are not confined to the basal cell layer ( Fig. 19.8 ). Any grade of CIN is potentially invasive, although the risk of invasion becomes greater as the severity of the lesion increases. The rate at which these intraepithelial lesions progress and the proportion of cases that would progress if left untreated is uncertain. The presence of abnormal mitotic figures is associated with progression. It is also the case that, in some young women, the lesions progress to invasive carcinoma more quickly (3 years or less). The categorisation of cervical neoplasia into low- (CIN 1) and high- (CIN 2 and 3) grade intraepithelial neoplasia reflects the clinical management of the disease.

The terms low-grade and high-grade squamous intraepithelial lesion are used in some countries, notably the USA ( Table 19.2 ).

Table 19.2

Classification of human papillomavirus–associated intraepithelial lesions of the cervix

Classification	Synonyms
‘Flat’ condyloma
CIN 1	Low-grade CIN	Mild dysplasia	Low-grade SIL
CIN 2	High-grade CIN	Moderate dysplasia	High-grade SIL
CIN 3	High-grade CIN	Severe dysplasia or carcinoma in situ	High-grade SIL

CIN , Cervical intraepithelial neoplasia; SIL , squamous intraepithelial lesion.

Cervical screening programmes

Cervical screening programmes are sometimes referred to erroneously as cervical cancer screening. This is incorrect because the aim is to detect atypical cells by cervical cytology in the preinvasive stage of the disease. The abnormal epithelium can then be eradicated by local measures, such as diathermy large loop excision of the transformation zone.

Cervical cytology is a simple, safe, noninvasive method of detecting precancerous changes in the cervix. The majority of specimens submitted to the pathology laboratory are taken from asymptomatic women as part of a national screening programme. The incidence of and mortality from invasive cervical cancer has fallen dramatically in communities where intensive screening has been carried out. The rates of cervical cancer would be at least 50% greater if there was no screening programme; attendance for regular screening prevents up to 90% of cervical cancer.

The examination of a cervical cytology specimen relies on the identification of abnormal (dyskaryotic) nuclei ( Fig. 19.9 ). The degree of abnormality may be low or high grade but does not always correlate with subsequent histological findings in a biopsy specimen. Therefore currently, there is triage of low grade cytology with testing for high risk HPV subtypes ( Table 19.3 ). Cytology is not a reliable means of detecting an invasive tumour; the diagnosis of invasive carcinoma of the cervix is largely clinical and is confirmed by biopsy of suspicious areas of the cervix. The morphological abnormalities of the nucleus (dyskaryosis) in cervical cytology specimens are:

• disproportionate nuclear enlargement

• irregularity in form and outline

• hyperchromasia

• irregular chromatin condensation

• abnormalities of the number, size and form of nucleoli

• multinucleation.

The cytology is in the form of liquid-based cytology, in which cells are received by the laboratory suspended in fluid and prepared as a near monolayer on a slide and stained.

Table 19.3

Outcomes of cervical cytology results

Open full size image

HPV , Human papillomavirus.

Invasive squamous carcinoma

The earliest sign of malignancy is early stromal invasion when small foci (less than 3 mm) are seen to arise from the basal epithelium and to breach the integrity of the basement membrane (see Fig. 19.7 ). The concept of an early invasive carcinoma is one in which there is a negligible risk of lymph node metastasis so that conservative management is appropriate. The tumour spreads by local and lymphatic invasion. The two principal factors that determine the prognosis of cervical carcinoma are:

• the size and depth of invasion of the primary tumour

• the presence and (importantly) the extent of lymph node metastases.

The staging of cervical cancer is based on clinical and pathological assessment ( Fig. 19.10 ).

The degree of histological differentiation of squamous carcinoma (whether it is well, moderately or poorly differentiated) is also an important factor.

Luteal phase insufficiency

In some cases of primary or secondary infertility, endometrium examined in the secretory or luteal phase of the cycle shows inadequate secretory maturation for the appropriate estimated postovulatory day. Glandular and stromal maturation may also appear to be out of phase (so-called ‘irregular ripening’). These changes are usually due to diminished production of progesterone by the corpus luteum.