Australian Society of CytologyCase of the Month
July 2002 - Answer and Discussion
Cervical endometriosis
A cervical biopsy was submitted for examination. The transformation zone was sampled and sections revealed orderly squamous and columnar epithelium. There was no evidence of dysplasia. However, the sections showed foci of endometriosis with endometrial glands surrounded by stroma.
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This is a higher power magnification of the section showing glands and stroma. The glands were lined with a single layer of mitotically inactive columnar cells. |
The stroma was interspersed with numerous lymphocytes but few haemosiderin laden macrophages were identified. Curettings from the patient comprised fragments of endometrium showing late proliferative to early secretory phase features. The cytological appearances of these cells were similar to that identified in the cervical tissue.
Endometriosis of the cervix is a potential pitfall in the evaluation of cervical smears. It is generally regarded as a rare lesion, but studies have cited an incidence as high as 2-3% in some series. The condition is related to previous surgical trauma, for example cautery or conization. In the absence of a history of surgical intervention, the presence of endometrial tissue in the cervix may be due to a metaplastic process.
Differential diagnosis includes adenocarcinoma of the endocervix, LUS cells and high grade CIN, benign endocervical and endometrial cells, atrophy, repair and tubal metaplasia.
Endometriosis and adenocarcinoma-in-situ of the endocervix share some characteristics on cytology.
Features favouring a diagnosis of AIS over endometriosis include:
- More irregular nuclei.
- Coaser chromatin.
- The presence of rosettes and papillary structures.
- Co-existing squamous atypia.
Presence of nucleoli in endometriosis may provoke consideration of invasive adenocarcinoma. However, the cells in invasive lesions show more pronounced nuclear features and are more dissociated. A tumour diathesis is usually apparent.
Click here for a more detailed description of the cytological features of adenocarcinoma of the endocervix.
Endometriosis and LUS cells share similar cytological features. Often it may be difficult to distinguish the two entities and a detailed clinical history, along with histological confirmation, may be required.
Features favouring a diagnosis of endometriosis include:
- Presence of larger tissue fragments with tubular glands and branching patterns.
- Nuclear crowding and peripheral palisading of nuclei.
- Round nuclei and finely granular chromatin.
- Presence of stromal cells and a capillary "network".
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This is a photograph of LUS cells showing a capillary network and associated stromal cells. |
High grade CIN involving glands also needs to be included in the differential diagnosis. The cells usually appear in clusters like endometriosis but the finding of individual carcinoma-in-situ type cells can be helpful in making the distinction.
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In high grade CIN, the groups have a syncytial architecture and show more worrisome nuclear features. |
The presence of benign endometrial cells due to abnormal shedding can create diagnostic difficulties. Compared to endometriosis the cells tend to be smaller, lack conspicuous nucleoli, are more tightly grouped in three-dimensional clusters and may show associated stromal cells.
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Sheets of lower intermediate and parabasal cells seen in atrophy may also mimic the entity as does epithelial repair. The cells in both conditions tend to have more abundant cytoplasm. |
Tubal metaplasia may pose a problem especially if large cell clusters are seen. The cells usually show cilia and terminal bars which are not usually seen in endometriosis. However, it must be remembered that endometriosis can show areas of tubal metaplasia.
Conclusion
Cervical endometriosis can be suggested if:
- The smear shows moderate to high glandular cellularity.
- Large tissue fragments are present with branching, peripheral palisading and "feathering".
- Absence of single cells, cilia, terminal bars, capillary "networks" and rosettes.
- The patient has a history of surgical intervention.
References
de Peralta-Venturino MN et al. Endometrial Cells of the "Lower Uterine Segment" (LUS) in Cervical Smears Obtained by Endocervical Brushings: A Source of Potential Diagnostic Pitfall
Diagn Cytopathol 1995;12:263-271.
Hanau CA et al. Cervical Endometriosis: A Potential Pitfall in the Evaluation of Glandular Cells in Cervical Smears.
Diagn Cytopathol 1997;16:274-280.
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