Introduction
Endometrial epithelial metaplasia is described as transition of the normal endometrial epithelial cells by benign complex proliferation of cells that are not normally seen in the endometrium. They are usually considered as inconspicuous elements. But since these metaplastic cells can sometimes appear atypical and unusual seen to be lining glands that are complex in architecture, this benign metaplastic process might be confused with endometrial adenocarcinoma. Also, these metaplastic changes have been frequently reported as associated changes in endometrial hyperplasia and adenocarcinoma more than non-neoplastic samples.1 Hence, it is essential to classify and device algorithms to distinguish these metaplastic changes from endometrial pathologies such as hyperplasia and malignancy. These metaplastic changes are often categorised as squamous, ciliated or tubal, papillary syncytial, eosinophilic, mucinous, hobnail and clear cell metaplasias.2
In this article, we report a case of endometrial eosinophilic metaplasia is presented along with a brief discussion on the defining characteristics of eosinophilic metaplasia and the differential diagnoses are discussed with an emphasis on immunohistochemistry.
Case Report
Endometrial biopsy from a 47-year-old patient, with complaints of menorrhagia, to look for any endometrial pathology. The patient had no other complaints. Microscopic examination of the endometrium showed large cells with eosinophilic cytoplasm and mildly pleomorphic nuclei arranged in sheets and attempted glandular patterns (Figure 1, Figure 2, Figure 3). A pathologic diagnosis of endometrial eosinophilic metaplasia was made. However, in view of the literature reporting too many cases of eosinophilic metaplasia associated with hyperplasia and malignancy, the patient was advised to follow up with immunohistochemical study of the biopsy, to rule out any endometrial pathology.
Discussion
Endometrial metaplasia, in recent times, termed as endometrial epithelial cytoplasmic change, and is described as an adaptive cytoplasmic change frequently seen in the endometrium. Eosinophilic cell change is one of the most frequently encountered endometrial metaplasias found in both neoplastic and nonneoplastic endometrium. Its phenotypic features and mechanisms of development have not yet been fully understood. They comprise 28% of all endometrial metaplasias including mucinous and ciliated metaplasias.3 Also, eosinophilic metaplasias were seen to be more commonly associated with endometrial pathologies such as hyperplasia and malignancy when compared with their occurrence in normal endometrium.2 Hence, it is important to rule out any endometrial pathology, especially malignancy, in endometrial samples showing eosinophilic metaplasia.
Eosinophilic syncytial change is a form of eosinophilic endometrial metaplasia, also referred to as papillary syncytial change, often found in association with endometrial breakdown and bleeding, especially in non physiological conditions. When prominent, this morphological change results in a pattern of eosinophilic endometrial cells, arranged in a pseudopapillary pattern that can resemble cellular changes found in atypical endometrium.4
Immunohistochemistry
Some cases of eosinophilic syncytial change show atypical cytologic features and hence may mimic endometrial carcinoma. Immunohistochemistry can help differentiate between the two. The Ki-67 labeling index, examined in a small series of cases including eosinophilic cell change, atypical endometrial hyperplasia and endometrial adenocarcinoma, was 1.3% in eosinophilic syncytial change cases, 15.8% in atypical endometrial hyperplasia, and 42.6% in endometrial adenocarcinoma. The mitotic index measured from pHH3 immunostaining, in a small series of cases including eosinophilic cell change, atypical endometrial hyperplasia and endometrial adenocarcinoma, was found to zero in all cases of endometrial syncytial change, while it was 2.3% in atypical endometrial hyperplasia and 4.8% in endometrial adenocarcinomas.4
Since the eosinophilic syncytial change tends to form pseudopapillary and glandular formations, they are often regarded as papillary syncytial change and sometimes pose challenges in differentiating them from serous papillary carcinomas. One study analysed immunohistochemical markers PTEN and p53 to serve this purpose. All cases of eosinophilic syncytial change exhibited moderate or strong staining for PTEN, while PTEN staining was absolutely negative in all endometrial serous carcinomas. Around 54% of cases of eosinophilic cell change show weak focal positive staining for p53, while all cases of endometrial serous carcinomas showed intense positivity for p53. Also, the Ki-67 index was low and was found in only 32% of cases with eosinophilic syncytial change but was high in all of the cases of endometrial serous carcinomas.5
Conclusion
In conclusion, we have presented a case of endometrial eosinophilic metaplasia in a 47-year-old patient along with a brief discussion on immunohistochemical characteristics of eosinophilic syncytial change that could help pathologists to differentiate them from malignancies in challenging scenarios.
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