Cellular Classification of Endometrial Cancer

The most common endometrial cancer cell type is endometrioid adenocarcinoma, which is composed of malignant glandular epithelial elements; an admixture of squamous metaplasia is not uncommon. Adenosquamous tumors contain malignant elements of both glandular and squamous epithelium;[1] clear cell and papillary serous carcinoma of the endometrium are tumors that are histologically similar to those noted in the ovary and the fallopian tube, and the prognosis is worse for these tumors.[2] Mucinous, squamous, and undifferentiated tumors are rarely encountered. Frequency of endometrial cancer cell types is as follows:

1. Endometrioid (75%–80%).
   1. Ciliated adenocarcinoma.
   2. Secretory adenocarcinoma.
   3. Papillary or villoglandular.
   4. Adenocarcinoma with squamous differentiation.
      1. Adenoacanthoma.
      2. Adenosquamous.
2. Uterine papillary serous (<10%).
3. Mucinous (1%).
4. Clear cell (4%).
5. Squamous cell (<1%).
6. Mixed (10%).
7. Undifferentiated.

1. Zaino RJ, Kurman R, Herbold D, et al.: The significance of squamous differentiation in endometrial carcinoma. Data from a Gynecologic Oncology Group study. Cancer 68 (10): 2293-302, 1991.  [PUBMED Abstract]
   
   
2. Gusberg SB: Virulence factors in endometrial cancer. Cancer 71 (4 Suppl): 1464-6, 1993.  [PUBMED Abstract]