Pathology of cancers of the female genital tract including molecular pathology

To better understand pathology reports, gynecologic oncologists must be familiar with the terminology used in gynecologic pathology. This chapter of the FIGO Cancer Report 2018 summarizes the clinical and pathological features of the most common cancers of the female genital tract, as well as their main molecular genetic alterations. In selected cases, an approach for processing surgical specimens is also included.


| Pathology
Squamous intraepithelial lesion VIN may be single or multiple, and macular, papular, or plaque-like. Histologic grades are labeled lowgrade SIL (VIN 1) corresponding to mild dysplasia, and high-grade SIL (VIN 2-3) corresponding to moderate, and severe dysplasia, respectively. However, high-grade SIL (VIN 3)-which includes squamous cell carcinoma in situ [CIS]-is by far the most common. This lesion is treated with wide excision.
Most tumors are exophytic, but some may be ulcerative.
Microscopically, the tumor is composed of invasive nests of malignant squamous epithelium with central keratin pearls (Fig. 2). The tumors generally grow slowly, extending to contiguous skin, vagina, and rectum. Typically, they initially metastasize to superficial inguinal lymph nodes, and then to deep inguinal, femoral, and pelvic lymph nodes. 1

| Verrucous carcinoma
Vulvar verrucous carcinoma is a distinct variety of squamous cell carcinoma that manifests as a large fungating mass resembling a giant condyloma acuminatum. HPV, usually type 6 or 11, is commonly identified. The tumor invades with broad tongues. Verrucous carcinomas rarely metastasize. Wide local surgical excision is the treatment of choice.

| Basal cell carcinoma
Basal cell carcinomas of the vulva are identical to their counterparts in the skin. They are not associated with HPV, rarely metastasize, and are usually cured by surgical excision.

| Malignant melanoma
Although uncommon, malignant melanoma is the second most frequent cancer of the vulva (5%). It occurs in the sixth and seventh decades, but occasionally is found in younger women. It is highly aggressive, and the prognosis is poor. Management should be according to guidelines for melanoma treatment elsewhere.

| Extramammary Paget disease
This disorder usually occurs on the labia majora in older women. The lesion is large, red, moist, and apparently sharply demarcated. The origin of the diagnostic cells (Paget cells) is controversial: they may arise in the epidermis or epidermally derived adnexal structures.
Intraepidermal Paget disease may have been present for many years and is often far more extensive throughout the epidermis than preoperative biopsies indicate. Unlike Paget disease of the breast, which is almost always associated with underlying duct carcinoma, extramammary Paget disease is less commonly associated with carcinoma of the skin adnexa (20%-30% of the time).
Metastases rarely occur, so treatment requires wide local excision or simple vulvectomy. 1

| Embryonal rhabdomyosarcoma (sarcoma botryoides)
Embryonal rhabdomyosarcoma occurs almost exclusively in girls under 4 years of age. It arises in the lamina propria of the vagina and consists of primitive spindle rhabdomyoblasts, some of which show cross-striations. Tumors less than 3 cm in greatest dimension tend to be localized and may be cured by wide excision and chemotherapy.
Larger tumors have often spread to adjacent structures, regional lymph nodes, or distant sites. Even in advanced cases, half of patients survive with radical surgery and chemotherapy. 1,2

| Squamous cell neoplasia
Cytological screening in high-resource countries has decreased cervical carcinoma by 50% to 85%; however, worldwide cervical cancer remains the fourth most common cancer in women. 6

| Cervical squamous intraepithelial neoplasia (SIL)
Cervical squamous intraepithelial neoplasia SIL (CIN) is a spectrum of intraepithelial changes that begins with minimal atypia and progresses through stages of greater intraepithelial abnormalities to invasive squamous cell carcinoma. The terms CIN, dysplasia, CIS, and squamous intraepithelial lesion (SIL) are commonly used interchangeably 1,2 (Fig. 3).

| Epidemiology and molecular pathogenesis
HPV infection with persistent expression leads to CIN and cervical cancer (Fig. 4). Low-grade SIL (CIN1) is a permissive infection (i.e. HPV is episomal, freely replicates, and thereby causes cell death). Huge numbers of virus must accumulate in the cytoplasm before being visible as a koilocyte (Fig. 3)

| Pathology
SIL CIN is nearly always a disease of metaplastic squamous epithelium in the transformation zone. The normal process by which cervical squamous epithelium matures is disturbed in CIN, as evidenced morphologically by changes in cellularity, differentiation, polarity, nuclear features, and mitotic activity. High-grade SIL (CIN3) is synonymous with severe dysplasia and CIS. The sequence of histologic changes from low-grade SIL (CIN1) to high-grade SIL (CIN2-3) is shown in Figure 3. 1,2

| Clinical features
The mean age at which women develop SIL (CIN) is 24-27 years for CIN1 and CIN2, and 35-42 years for CIN3. Based on morphologic criteria, half of cases of low-grade SIL (CIN1) regress, 10% progress to high-grade SIL (CIN3), and less than 2% become invasive cancer.
The average time for all grades of dysplasia to progress to high-grade SIL (CIN3) is about 10 years. At least 20% of cases of high-grade SIL (CIN3) progress to invasive carcinoma in that time. 1 When SIL (CIN) is discovered, colposcopy delineates the extent of the lesion and indicates areas to be biopsied. Diagnostic endocervical curettage also helps to determine if there is endocervical involvement.
Women with low-grade SIL (CIN1) are often followed conservatively (i.e. repeat Pap smears plus close follow-up). High-grade lesions are treated with excision LEEP (loop electrosurgical excision procedure), cervical conization (removal of a cone of tissue around the external os), ablation such as laser, cryosurgery, thermal coagulation, or rarely, hysterectomy may be done. 1

| Microinvasive (superficially invasive) squamous cell carcinoma
This is the earliest stage (IA) of invasive cervical cancer. In this setting, stromal invasion usually arises from overlying SIL (CIN) (Fig. 5).
Presently, staging of microinvasive disease is based on width and depth of invasion, defined as follows: 1. Invasion less than 3 mm (Stage IA1) or 5 mm (stage IA2) below the basement membrane.

7-mm maximum lateral extension.
The earliest invasive changes ("early stromal invasion" or ESI) appear as tiny irregular epithelial buds emanating from the base of CIN3 lesions. These small (<1 mm) tongues of neoplastic epithelial cells do not affect the prognosis of CIN3 lesions. In the 2009 FIGO classification, ESI was excluded from Stage IA1. Some gynecologic oncologists further limit microinvasive carcinoma to tumors lacking lymphovascular space invasion (LVSI). Stage IA2 tumors are associated with lymph node metastases in about 8% of cases whereas those that invade less than or equal to 3 mm (Stage IA1) have less than a 1%-2% risk of lymph node metastases. Conization or simple hysterectomy generally cures microinvasive cancers less than 3 mm deep. 1,5 The role of LVSI as a prognostic indicator is more controversial than (3) through lymphatic vessels; and (4) only rarely by the hematogenous F I G U R E 3 Interrelations of naming systems in precursor cervical lesions. This chart integrates multiple aspects of the disease. It illustrates the changes in progressively more abnormal disease states and provides translation terminology for the dysplasia/carcinoma in situ (CIS) system, cervical intraepithelial neoplasia (CIN) system, and The Bethesda system. The scheme also illustrates the corresponding cytologic smear resulting from exfoliation of the most superficial cells as well as the equivalent histopathologic lesions (top). Abbreviation: SIL, squamous intraepithelial lesion.

| Clinical features
HPV testing is the most reliable screening test for detecting cervical cancer, and is supplanting cytology in some screening algorithms in women aged over 25 years. Co-testing with HPV testing and cytology is also recommended in women aged over 30 years. Where HPV testing is not available, the Pap smear remains the most commonly used screening test, but quality assurance is a vital component of such

| Endocervical adenocarcinoma
This tumor makes up 20% of cervical cancers. The incidence of cervical adenocarcinoma has increased recently, with a mean age of 56 years at presentation. Most tumors (70%) are HPV-associated adenocarcinomas of endocervical cell (usual) type that may exhibit foci of adenocarcinoma in situ. 1,2 HPV-unrelated types (gastric-type and clear cell carcinoma) are less common and behave more aggressively than HPV-associated tumors.
Adenocarcinoma in situ (AIS) generally arises at the squamocolumnar junction and extends into the endocervical canal. This lesion may not always be contiguous and can be multifocal. Invasive adenocarcinoma typically presents as a polypoid or papillary mass. It is often not visible and presents somewhat later than its squamous counterpart.
Adenocarcinoma of the endocervix spreads by local invasion and lymphatic metastases, and overall survival is somewhat worse than for squamous carcinoma.

| Cervical cone biopsy/excision and trachelectomy
Cone biopsy is the standard procedure performed for women with high-grade CIN and glandular lesions (Fig. 6). The conventional cone biopsy is obtained using a scalpel ("cold knife"), but today it is more often used for glandular lesions. Ectocervical lesions are best F I G U R E 5 Superficially invasive squamous cell carcinoma. The tumor invades less than 5 mm deep and 4 mm wide. This tumor is Stage IA2 according to FIGO's classification.

| Endometrial hyperplasia
Endometrial hyperplasia forms a morphologic continuum of abnormal proliferation ranging from focal glandular crowding or simple hyperplasia to well-differentiated adenocarcinoma.

| Hyperplasia without atypia
This is an exaggerated proliferation of glands of irregular size and shape with increase in the gland-to-stroma ratio compared with proliferative endometrium, but without significant nuclear atypia. Risk factors include obesity, polycystic ovarian disease, and diabetes. Hyperplasia without atypia is the result of unopposed estrogenic stimulation.
Patients have a 3-4-fold increased endometrial carcinoma risk, rising to 10-fold after 10 years. Progression to endometrial carcinoma occurs in 1%-3% of women with hyperplasia without atypia.

| Atypical hyperplasia/endometrial intraepithelial neoplasia (EIN)
This lesion shows marked glandular crowding, often as back-to-back glands, with little intervening stroma and cytologic atypia. Epithelial cell nuclei are large and hyperchromatic with prominent nucleoli. Onequarter to one-third of these women will be diagnosed with endometrioid carcinoma at immediate hysterectomy or during the first year of follow-up. 2  EIN refers to a monoclonal neoplastic growth of genetically altered cells with greatly increased risk of becoming the endometrioid type of endometrial carcinoma. The main diagnostic criterion of EIN is that gland area exceeds that of stroma (volume percentage stroma <55%).

| Clinical features
Hysterectomy is usually the therapy of choice if a woman does not want more children. Women who want more children or those with high operative risks may be treated with progestins in selected cases.

| Endometrial carcinoma
Endometrial carcinoma is the sixth most frequent cancer diagnosed in women globally, with an age standardized incidence rate of 8.2 per 100 000. It is the fourth most common cancer in women in industrialized countries and the most common gynecologic cancer. Threequarters of women with endometrial cancer are postmenopausal. The median age at diagnosis is 63 years. 1,2 Endometrial carcinoma is classified into two different types ( Fig. 7 and Table 1). Type I tumors ( Endometrial cancer is the most common extracolonic cancer in women with hereditary nonpolyposis colon cancer syndrome (also known as Lynch syndrome)-a defect in DNA mismatch repair that is also associated with ovarian, urothelial, and breast cancers. 10
Nonendometrioid carcinomas may also derive from endometrioid carcinoma with microsatellite instability through tumor progression and subsequent p53 mutations. 10 The Cancer Genome Atlas (TCGA) has conducted the most comprehensive genomic analysis of endometrial carcinomas reported to date. 11 TCGA has expanded the dualistic classification of endometrial carcinoma (types I and II) to four distinct molecular subgroups: (1)  Molecular classification of grade 3 endometrial endometrioid carcinomas reveals that these tumors are a mixture of molecular subtypes of endometrial carcinoma, rather than a homogeneous group. Molecular markers identify prognostic subgroups, with therapeutic implications.

| Endometrioid carcinoma of the endometrium
This type of endometrial cancer is composed entirely of glandular cells and is the most common histologic variant (80%-85%). The FIGO system divides this tumor into three grades on the basis of the ratio of glandular to solid elements, the latter signifying poorer differentiation.
Less common histologic variants include endometrioid adenocarcinoma with squamous differentiation and the mucinous and secretory types, both associated with good prognosis. 1-3,5

| Nonendometrioid endometrial carcinomas
These are aggressive as a group, and histologic grading is not clinically useful, all cases being considered high grade.
1. Serous carcinoma histologically resembles, and behaves like, high-grade serous carcinoma of the ovary (Fig. 7B). It often shows transtubal spread to peritoneal surfaces. An intraepithelial form has been termed "serous endometrial intraepithelial carcinoma" (serous EIC), not to be confused with EIN, described earlier.
Patients with this type of tumor need to be staged and treated as if they had ovarian cancer.

| Clinical features
Unlike cervical cancer, endometrial cancer may spread directly to para-aortic lymph nodes, thereby skipping pelvic nodes. Patients with advanced cancers may also develop pulmonary metastases (40% of cases with metastases).
Women with well-differentiated cancers confined to the endometrium are usually treated by simple hysterectomy and frequently bilateral salpingo-oophorectomy. Postoperative radiation is considered if: (1) the tumor is poorly differentiated or nonendometrioid in type; (2) myometrium is deeply invaded (more than 50% of the myometrium); (3) the cervix is involved; or (4) lymph nodes contain metastases.
Survival in endometrial carcinoma is related to multiple factors: (1) stage, histologic type, and, for endometrioid tumors, grade; (2) age; and (3) other risk factors, such as progesterone receptor activity, depth of myometrial invasion (Fig. 8), and extent of lymphovascular invasion. 12 Actuarial survival of all patients with endometrial cancer following treatment is 80% after 2 years, decreasing to 65% after 10 years. Serous carcinomas have an overall survival of less than 50% and account for more than half of the mortality from this disease.
Tumors that have penetrated the myometrium or invaded lymphatics are more likely to have spread beyond the uterus. Endometrial cancers involving the cervix have a poorer prognosis. Spread outside the uterus entails the worst outlook. 5,12 As of 1988, this is a surgically staged disease.

| Endometrial sarcomas
Currently, endometrial sarcomas are classified into three categories: of patients with adenosarcoma, particularly cases with myometrial invasion and sarcomatous overgrowth, eventually succumb to local recurrence or metastatic spread. 1,2

| Leiomyosarcoma
Leiomyosarcoma is a malignancy of smooth muscle origin whose incidence is only 1/1000 that of leiomyoma. It accounts for 2% of uterine malignancies. Its pathogenesis is uncertain. Women with leiomyosarcomas are on average more than a decade older (age above 50 years) than those with leiomyomas, and the malignant tumors are larger (10-15 cm vs 3-5 cm). 1,2

| Pathology
Leiomyosarcoma should be suspected if an apparent leiomyoma is soft, shows areas of necrosis on gross examination, or has irregular borders (invasion of adjacent myometrium). Mitotic activity (10 or more mitoses per 10 HPFs), nuclear atypia, and geographical necrosis are the best diagnostic criteria (Fig. 9A,B). Myxoid and epithelioid leiomyosarcomas may contain only five mitoses per 10 HPFs. Size is important as tumors less than 5 cm in diameter almost never recur.
Most leiomyosarcomas are large and are advanced when detected. cases. The latter term simply describes the morphologic findings avoiding the words "uncertain" and "malignant," which create unnecessary concern for the patient.
In two studies of 41 and 16 cases of "STUMP," only 3 (7%) and 2 (12%) patients developed recurrences, respectively. Recurrence occurred, several years after hysterectomy, in the form of "STUMP" in three cases and as leiomyosarcoma in the other two. All five patients were alive and disease free after prolonged follow-up. 13

| Risk reducing salpingo-oophorectomy
An increasingly common indication for salpingectomy is prophylac- The protocol for sectioning and extensively examining the fimbriated end (SEE-FIM protocol) (Fig. 10) was developed for processing risk-reducing salpingo-oophorectomy specimens. 16 The entire tube is initially fixed for at least 4 hours to prevent denuding of the mucosal epithelial cells. Then, the fimbriated end is amputated from the proximal tube and sectioned longitudinally into multiple (at least four) sections and the entire tube is submitted for histologic review. 1

| Epithelial tumors
Tumors of common epithelial origin can be broadly classified, according to cell proliferation, degree of nuclear atypia, and presence or absence of stromal invasion: (1) benign; (2) borderline malignancy; and (3) carcinoma.

| Borderline tumors
Borderline tumors show epithelial proliferation greater than that seen in their benign counterparts and variable nuclear atypia; however, in contrast to carcinomas, there is absence of stromal invasion, and their prognosis is much better than that of carcinomas. Despite the lack of ovarian stromal invasion, serous borderline tumors-particularly those with exophytic growth-can implant on peritoneal surfaces (Fig. 12A) and, rarely, (about 10% of peritoneal implants), progress to LGSC and invade the underlying tissues (Fig. 12B).

| Pathology
High-grade serous carcinomas are the most common ovarian cancers and most patients present with advanced stage disease (approximately 80%). Two-thirds of serous cancers with extraovarian spread are bilateral. They are predominantly solid masses, usually with necrosis and hemorrhage and typically show obvious stromal invasion.
Most tumors have a high nuclear grade with highly cellular papillae and solid areas (Fig. 13A). The mitotic rate is very high. Psammoma low-and high-grade serous carcinomas (Fig. 13B)

| Endometrioid carcinoma
Endometrioid adenocarcinoma histologically resembles its uterine counterpart (Fig. 13D), may have areas of squamous differentiation, and is second only to serous adenocarcinoma in frequency.
It accounts for 10% of all ovarian cancers. These tumors occur most commonly after menopause. Up to half of these cancers are bilateral and, at diagnosis, most tumors are either confined to the ovary or within the pelvis. 1,2

| Molecular pathogenesis
Endometrioid carcinomas are thought to arise by malignant transformation of endometriosis, and not from ovarian surface epithelium.
The most common genetic abnormalities in sporadic endometrioid carcinoma of the ovary are somatic mutations of the ARID1A, β-catenin (CTNNB1), and PTEN genes and microsatellite instability.

| Pathology
Although they may be cystic, most endometrioid carcinomas are largely solid with areas of necrosis. These tumors are graded like their uterine counterparts. Between 15% and 20% of patients also harbor a uterine endometrioid carcinoma. Strong data suggest that

| Choriocarcinoma
Choriocarcinoma of the ovary is a rare tumor that mimics the epithelial covering of placental villi, namely, cytotrophoblast and syncytiotrophoblast. The pregnancy test is positive and the elevated serum level of human chorionic gonadotropin may lead to precocious sexual development in young girls or menstrual abnormalities in older patients. In women of reproductive age, however, it may also be a metastasis from an intrauterine gestational tumor. The tumor is unilateral, solid, and widely hemorrhagic. Although highly aggressive, it responds well to chemotherapy. 1,2

| Sex cord/stromal tumors
These tumors represent 10% of ovarian tumors, vary from benign to low-grade malignant, and may differentiate toward female (granulosa and theca cells) or male (Sertoli and Leydig cells) structures. 1,2

| Granulosa cell tumor
Granulosa cell tumors are the prototypical functional neoplasms of the ovary associated with estrogen secretion. They should be considered low-grade malignancies because of their potential for local spread and the rare occurrence of distant metastases.
Most granulosa cell tumors occur after menopause (adult form) and are unusual before puberty. A juvenile form occurs in children and young women and has distinct clinical and pathologic features (hyperestrinism and precocious puberty).

| Pathology
Adult-type granulosa cell tumors are large and focally cystic to solid. The cut surface shows yellow areas, due to lipid-rich luteinized granulosa cells, white zones of stroma, and focal hemorrhages. Random nuclear arrangement about a central degenerative space (Call-Exner bodies) gives a characteristic follicular pattern. Tumor cells secrete α-inhibin, a protein that suppresses pituitary release of follicle-stimulating hormone (FSH). Besides α-Inhibin, calretinin, and FOXL2 are the most important positive immunoreactions. 1,2 The most common chromosomal abnormalities are trisomy 12, trisomy 14, monosomy 16, deletion of 16q, and monosomy 22. Missense somatic point mutations in the FOXL2 gene (402 C to G) are found in over 90% of adult granulosa cell tumors.

| Clinical features
Three-fourths of granulosa cell tumors secrete estrogens.
Thus, endometrial hyperplasia is a common presenting sign.