Squamous differentiation can be appreciated in this neoplastic endometrial gland. Note the increased eosinophilic cytoplasm.
In this moderate to poorly differentiated endometrioid adenocarcinoma, the squamous portions are also moderate to poorly differentiated. The grade of the squamous areas usually mirrors the grade of the glandular portion.
Obviously malignant squamous features can be seen in this area - note the size difference in the nuclei. The cell borders are quite clear.
Yet another image demonstrating squamous differentiation in the form of increased cytoplasm and a polygonal shape to the cell.
Squamous differentiation is found in up to 50% of endometrioid endometrial adenocarcinomas (EA), making this the most common variant seen in EA. Historically, these entities were called either adenocanthoma (if the squamous component was well-differentiated) or adenosquamous carcinomas (if the squamous component was poorly-differentiated).1
Currently, the preferred term is endometrioid adenocarcinoma with squamous differentiation. The pathologist should focus on the glandular component only when grading the tumor. Research has shown that for the most part, the squamous component mirrors the glandular component in terms of grade. For example, poorly-differentiated glands are associated with poorly-differentiated squamous areas with irregular sheets of frankly malignant squamous cells. Well-differentiated glandular lesions have well-differentiated squamous areas consisting of squamous morules, sometimes with central necrosis and keratinization.1-3
There seems to be no difference in prognosis for adenocarcinoma with or without squamous elements.
1 Nucci MR, Oliva Esther. Gynecologic Pathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elsevier: 2009:
2 Zaino RJ, Kurman RJ. Squamous differentiation in carcinoma of the endometrium: a critical appraisal of adenoacanthoma and adenosquamous carcinoma. Semin Diagn Pathol. 1988 May;5(2):154-71.
3 Zaino RJ, Kurman R, Herbold D et al. The significance of squamous differentiation in endometrial carcinoma. Data from a Gynecologic Oncology Group study. Cancer. 1991 Nov 15;68(10):2293-302.
4 Pekin T, et al. Adenocarcinoma, adenoacanthoma, and mixed adenosquamous carcinoma of the endometrium.Eur J Gynaecol Oncol. 2001;22(2):151-3.