Fig. 12  Tumor growth and vaginal opacification. T2w TSE image in sagittal orientation. The high-signal-inten- sity cervical cancer has a central necrotic cavity (asterisk) with an air-fluid level. There is barrel-shaped expansion of the cervix and portio through the tumor. Tumor growth into the uterine cavity (arrow). Accessory finding: leiomyoma of the uterine corpus (open arrow). The vagina and fornix are distended by gel, which allows exclusion of vaginal infiltration

planning brachytherapy. The insertion of a vaginal tampon soaked with contrast medium has been abandoned because distention of the vagina is incomplete while anatomic relationships are distorted. However, intravaginal application of a contrast medium, e.g., ultrasound gel as a negative contrast medium (Fig. 13), was found to improve evaluation of vaginal involvement and is part of the routine protocol in many centers.

2.3\ Staging

2.3.1\ General MR Appearance

The basis of the radiologic evaluation of cervical cancer is T2-weighted MRI sequences (Shiraiwa et al. 1999), which provide high soft-tissue contrast for optimal differentiation of tumor from normal cervical stroma and adjacent organs. Cervical cancer is characterized by a higher ­signal intensity and is thus delineated against the cervical stroma, which has a lower signal

intensity. Cervical cancer typically develops as a circumscribed focal lesion arising from the mucosal layer of the cervix. It may grow superficially in a circular pattern and increases in depth with invasion of the cervical stroma. Sagittal and transverse T2-weighted sequences serve to determine the localization and size of the tumor as well as the depth of cervical stroma infiltration. These sequences are also crucial for excluding extracervical extension and infiltration of the parametria, vagina, bladder, and rectum. The two critical issues—depth of infiltration and parametrial involvement—can be assessed most reliably on transverse images angulated perpendicular to the cervical axis.

Cervical cancer arises in the transitional zone that marks the junction of the squamous epithelium of the external cervix with the columnar epithelium of the cervical canal. This zone is usually located on the portio in younger women, which is where cervical cancer usually occurs with exophytic growths. In contrast, older women with retraction of the transformation zone into the cervical canal typically develop cervical cancer with an endocervical growth pattern (Fig. 13). This growth type usually gives rise to the typical bar- rel-shaped configuration of the cervix as the tumor increases in size or an endocervical ulcer develops when there is necrosis.

On T1-weighted MR images, cervical cancer is similar in signal intensity to the normal cervical stroma. Demarcation from the corpus uteri, vagina, and parametria is also difficult (Fig. 14). Only large cervical carcinomas can be identified based on their mass effect.

However, T1-weighted images can be useful in delineation of the tumor within the lateral parametria, which have a higher fat content than the medial parametria, resulting in improved contrast between high-signal-intense fat and low- signal-intense carcinoma. In the routine clinical setting, T1-weighted sequences are primarily used for lymph node staging and for unenhanced imaging in cases where contrast medium administration is planned.

Cervical carcinomas show early enhancement 15–30 s after contrast medium administration.

Fig. 13  Comparison of T2w and T1w imaging. (a, b) T2w TSE images in sagittal and transverse orientation showing stage IIB cancer of the posterior cervix. There is posterior (sagittal) and left lateral (transverse) disruption of the hypointense cervical stroma (arrows). (c, d) T1w

TSE images with FS in identical sagittal and transverse orientation. The extent of the cervical cancer in the stroma cannot be assessed due to the lower soft-tissue contrast of T1w sequences

The increase in signal intensity can improve the contrast between the hypointense cervical stroma and the hyperintense tumor on T1-weighted images. Altogether, however, the signal intensity of cervical cancer is heterogeneous and varies with vascularization. In pretherapeutic staging where precise determination of the extent of the tumor in the cervix and its relationship to the cor-

pus uteri, parametrial tissue, and vagina is important, most cervical carcinomas are seen more clearly on T2-weighted images than on contrastenhanced T1-weighted images. This does not hold true for advanced cervical carcinomas with infiltration of the bladder or rectum or extension to the pelvic sidewall and for the exclusion of recurrent tumor by post-therapeutic MRI.

Fig. 14  Determination of tumor size. (a, b) T2w TSE images in sagittal and transverse orientation (arrows) with barrel-shaped expansion of the cervix. Maximum tumor

diameter is determined according to the RECIST criteria of the WHO, in the example on the sagittal image (line)

2.3.2\ Rare Histologic Types

Squamous cell carcinoma is by far the most common histologic type, accounting for about 90% of all cervical carcinomas. Descriptions in this chapter and in the literature on cervical cancer in general usually refer to this histologic type, unless explicitly stated otherwise. In this section, other histologic types of cervical cancer, especially adenocarcinoma, are briefly described with regard to their clinical status and imaging features (see also Sects. 1.5 and 2.6). In general, it is not possible to distinguish these less common histologic types from squamous cell carcinoma of the cervix based on their MR appearance.

With a proportion of 10–15% of all cervical cancers, adenocarcinoma is the most frequent of the rarer histologic types. The histologic distinction is important. Adenocarcinomas arise from the columnar epithelium and are associated with a higher risk of infiltration of the uterine corpus, lymphatic spread, and local recurrence compared with squamous cell carcinoma. Adenocarcinoma is more difficult to demonstrate histologically, which is why the diagnosis is often delayed until the tumor has reached an advanced stage. The clinical and radiologic evaluation of tumor extent

also presents a challenge, as some adenocarcinomas are characterized by subepithelial growth and diffuse infiltration. Parametrial infiltration is not always associated with a macroscopic disruption of the cervical stroma. A focal lesion is not always apparent on MRI since small adenocarcinomas often grow diffusely and have a signal intensity similar to that of normal cervical tissue. The morphologic MR appearance varies with the histologic subtype. Mucinous adenocarcinoma is the most common subtype and may be endocervical or ectocervical in location. T2-weighted images show a tumor with an intermediate to slightly hyperintense signal intensity, depending on the mucin content. The margin is irregular and blurred. The second most common subtype is adenoma malignum, an extremely well-differentiated mucinous adenocarcinoma that is very difficult to confirm histopathologically. Adenoma malignum is composed of clusters of cystic lesions within an otherwise more or less solid tumor tissue of high signal intensity. The solid portions are key to the differentiation from dilated cervical glands and nabothian cysts. Other histologic subtypes are endometrioid, clear cell, and serous adenocarcinoma of the cervix,