January 2009
Feature Story

A new book is out: College of American Pathologists Practical Guide to Gynecologic Cytopathology. Morphology, Management, and Molecular Methods. Yes, many monographs, textbooks, and atlases already cover morphology and methods in gynecologic cytology. But with individual proficiency testing having been mandated since 2005, members of the CAP Cytopathology Committee decided that an updated practical manual covering the basics and advanced practice was needed, and it is this group of cytopathologists who took on the task of building it.

“Practitioners, especially those who have been away from the field for long periods or who practice gynecologic cytology as only a small piece of their overall practice, need an image-intense guide with cogent explanations that is applicable to both their daily work and to ‘brush up’ prior to the proficiency test itself,” the editors, David C. Wilbur, MD, and Michael R. Henry, MD, wrote in the preface.

The manual covers the basic principles of gynecologic cytology, including an approach to evaluating a patient and the accompanying specimen; criteria to determine specimen adequacy; normal elements; and the morphology of the benign and malignant entities that will be identified routinely in Pap tests. The morphology-based chapters are heavy on “look-alikes” and “spectrums” of cellular changes, and, here in CAP TODAY, we provide you with a sampling of that—it is, after all, what makes this manual stand out from the rest.

Look-alikes and morphologic spectrums of change

A chapter by Michael R. Henry, MD; Amy C. Clayton, MD; and Camilla J. Cobb, MD. Following are their introductory comments. The figures presented here (4, 8, 26, and 27) are just four of 28 that make up this chapter.

It is remarkable that such a small area of the body, the cervix, provides such a broad range of cytologic findings. The previous chapters have delineated the various epithelial abnormalities, organisms, benign changes, and artifacts that can be found on cytologic specimens from the cervical/vaginal area. This chapter will look at some of these same findings in a different way.

First, almost all of the previously described entities share similar cytologic features with other entities or artifacts. These look-alikes must always be considered when evaluating Pap slides, and the next pages will focus on some of the more common and significant entities and their mimickers.

Second, all of the epithelial abnormalities found on Pap slides fall within spectrums of cytologic change that range from benign to frankly malignant. Our diagnostic classification schemes, both historical and current (the Bethesda System), set up well-defined categories, but, in reality, many cellular presentations fall into gray zones between these specific diagnoses. It has always been recognized that epithelial abnormalities, especially squamous lesions, begin with minimal abnormal cytologic change and progress over time to more significant findings and eventually to invasive carcinoma. As our knowledge of the role of human papillomavirus in cervical disease has evolved, we can now recognize why some morphologic changes look as they do. This has allowed for the development of nomenclature (the Bethesda System) that enables clinical follow-up in a standardized appropriate fashion (American Society for Colposcopy and Cervical Pathology guidelines). These morphologic spectrums occur both between diagnostic categories (such as NILM [negative for intraepithelial lesion or malignancy]—ASC-US [atypical squamous cells of undetermined significance]—LSIL [low-grade squamous intraepithelial lesion]—HSIL [high-grade squamous intraepithelial lesion]) as well as within a specific diagnosis (eg, the spectrum of nuclear changes in AIS [adenocarcinoma in situ]). Recognizing the existence of these spectrums is necessary for an understanding of the practice of gynecologic cytology and will aid the cytologist in formulating appropriate diagnostic interpretations.

Reactive changes
Fig. 4. Follicular cervicitis (PDF 128 KB)

Follicular cervicitis (FC) typically involves only a portion of the Pap slide and is composed of a polymorphic population of lymphocytes and a few tingible body macro­phages (ie, macrophages with phagocytized debris) (A). FC is readily recognized in well-preserved preparations, but confusion with other small cell lesions is a problem when there is poor preservation and/or degeneration. In cases of lymphoma or leukemia, which rarely present in Pap slides and almost always as a metastatic rather than primary malignancy, tumor cells usually dominate the specimen and show a more monomorphic population of large lymphoid cells with irregularly distributed granular chromatin and prominent nucleoli (B). Apoptotic cells are also often seen in cases of lymphoma/leukemia and are typically absent in FC. Likewise, small cell carcinoma would also dominate the Pap slide and show small tumor cells singly and in cell clusters, with molding and chain formation (C). Because of their cohesiveness and epithelial attachments, rather than the loose cluster formation seen in follicular cervicitis, hyperchromatic crowded groups of squamous cells (eg, HSIL [D] or endometrial cells [E]) are less often confused with FC.

Squamous lesions
Fig. 8. HSIL: Single small cells (PDF 245 KB)

The cells of HSIL may present as single cells, sheets, crowded groups, or most often as a combination of all three. One of the characteristics of dysplasia is the loss of cohesion in the cells and thus the tendency for isolated single cells. A hallmark of HSIL is the decreasing overall size of the cell as the grade of the lesion increases, with a concomitant increase in the N:C ratio. In conventional Pap smears, these single cells were often geographically located in loose groups or within strands of mucous. With the advent of liquid-based preparations, these single cells are much more evenly disbursed throughout the preparation and are often difficult to identify on screening.

More germane to this section, there are many types of small isolated cells derived from other entities that may mimic HSIL. These include nonepithelial cells such as histiocytes or lymphocytes. Histiocytes (B) have small nuclei with even chromatin and often a coffee-bean shape with a prominent longitudinal groove. Small lymphocytes with their characteristic, very small nuclei should not be mistaken for HSIL. However, larger germinal center lymphocytes (C1) or lymphoma (C2 and 3) may be mistaken for squamous dysplasia. Germinal center cells are often accompanied by tingible body macro­phages as seen in follicular cervicitis. These cells do not have the membrane notching of HSIL and often have a more coarsely granular chromatin pattern.

Epithelial cells that may be confused with HSIL include reserve cells, parabasal cells, and immature squamous metaplastic cells (D). These cells are cytologically quite similar to each other and can be distinguished from HSIL by the lower N:C ratios, lack of significant membrane notching or irregularity, and normochromasia. Singly, the cells of ASC-H (atypical squamous cells, cannot exclude HSIL) may be indistinguishable from those of HSIL, as they have, by definition, features of HSIL but are qualitatively or quantitatively insufficient for a definitive diagnosis. Other single epithelial cells that can mimic HSIL include cells derived from IUD (intrauterine device) effect (E), single-cell pattern in AIS (F), and, rarely, metastatic tumors such as from breast (G). All of these are described in detail in chapters 4 and 6.

Morphologic glandular spectrums
Fig. 26. Tubal metaplasia: Spectrum of morphologic features (PDF 245 KB)

Tubal metaplasia can present with many morphologic appearances, depending on the preparation type and the degree of preservation within the cytology specimen. Conventional preparations will produce flatter, more open cell groups in which the nuclear features, cilia, and terminal may be more readily appreciated (A1). Liquid-based preparations allow the cell groups to round up and become more three-dimensional (A2). Tubal metaplasia is often easy to recognize in cytology specimens because of the presence of cilia or terminal bars (A3). However, mechanical disruption of the cell groups by sampling and smearing may disrupt or remove the cilia (B). When degenerative changes are superimposed on these types of cell groups, they may take on the appearance of atypical glandular cells (C). Tubal metaplasia that originates from the upper endocervical canal typically demonstrates higher N:C ratios (tuboendometrioid metaplasia). These groups demonstrate significant crowding and hyperchromasia on Pap specimens (D). Finally, some cases of tubal metaplasia may demonstrate nuclear elongation, hyperchromasia, and nuclear palisading. This overlap can very closely mimic AIS (E).

Fig. 27. Endocervical adenocarcinoma in situ: Spectrum of morphologic features (PDF 178 KB)

The cell groups of adenocarcinoma in situ may not always demonstrate classic features. Some groups may retain cytoplasmic mucin (A). Additional features that may lend a “reactive” endocervical cell appearance include slightly more open chromatin pattern with small visible chromocenters (B), or more abundant cytoplasm reducing the degree of nuclear crowding (C). The abnormal acinar ar­range­ments, nuclear shape, and three-dimensional appearance help to identify these groups as abnormal.

The endometrioid variant of AIS has smaller nuclei (8 to 10 μm²) and typically scant cytoplasm, bringing directly sampled LUS into the differential diagnosis (D). Close inspection will reveal significant nuclear hyperchromasia and architectural arrangements that support a diagnosis of AIS. The intestinal variant of AIS contains true goblet cells and resembles colonic adenocarcinoma (E).

Some cases of AIS may include cellular groups that have more rounded or angulated nuclei or chromatin granules that are coarser and larger than are typically present in AIS (F). These are nuclear features that are more commonly noted in squamous carcinoma in situ (CIS). While the nuclear polarization and acinar arrangements may help to confirm a glandular nature for the abnormal groups, these same architectural features can occasionally be seen in CIS involving endocervical glands. Finally, some AIS lesions are characterized by marked pleomorphism, including nuclear size variation, angulation, and visible nucleoli (G).