Epithelial tumors - benign
Endometrial polyp with atypical (bizarre) stromal cells

Authors: Vijay Shankar, M.D. (see Authors page)

Revised: 7 June 2016, last major update February 2012

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed search: Endometrial polyp atypical stromal cells
Definition / General
  • Usually an incidental finding
  • Represents a potential diagnostic pitfall
  • Can be misinterpreted as malignant in biopsy samples
Essential Features
  • Mean age 56 years (range 45 - 82 years)
  • Patients present with post-menopausal bleeding
  • Focal, multifocal or diffuse presence of atypical / bizzare cells in the stroma
  • Benign behavior; not associated with endometrial carcinoma
  • Atypia probably represents degenerative change
  • The atypical cells represent a primitive cell population arising from multipotent mesenchymal cells; can also be due to reactive or degenerative process (Am J Surg Pathol 2002;26:505)
Clinical Features
  • Presents with abnormal uterine bleeding
  • Simple curettage or biopsy may be sufficient, but due to paucity of published reports, follow up is necessary
Gross Description
  • The endometrial polyps can be functional, adenomyomatous, atrophic or hyperplastic types
  • Rarely, is a mixture of endometrial and endocervical polyps
Micro Description
  • Atypical cells may be scattered throughout the polyp, and can be focal, multifocal or diffuse
  • They can be seen beneath the surface epithelium or at the base / tip of the polyps
  • Moderate to severe nuclear atypia is due to large, hyperchromatic nuclei and occasional multinucleation
  • Hyperchromasia is due to "smudging", as with symplastic leiomyomas
  • No prominent nucleoli are seen
  • No mitotic activity
  • Giant cells often within loose fibrous background
  • May also be associated with a leiomyoma (Int J Gynecol Pathol 2005;24:352)
Micro Images

Images hosted on PathOut server:

Endometrial polyp with pseudosarcomatous stromal atypia: lesion is polypoid; large, often multinucleated cells with large hyperchromatic nuclei are present; these findings were limited to this polyp in a hysterectomy specimen, and mitotic figures were absent; the lesion never became more cellular than in this field; no densely cellular cuffs were noted around endometrial glands

Images hosted on other servers:

Bizzare stromal cells in endometrial polyp in a postmenopausal woman (fig 3)

Positive Stains
Differential Diagnosis
  • Adenosarcoma: stromal hypercellularity, periglandular stromal cuffing, cambium layer, polypoid or leaf-like projections into glandular lumina and > 3 mitoses / 10 high power fields
  • Atypical trophoblastic cells
  • Endometrial stromal sarcoma: tan to yellow, tightly packed spindled cells without significant glandular elements, smaller capillary type vessels distributed evenly; infiltrates into myometrium; usually no atypical cells
  • MMMT: malignant appearing epithelial component, stromal component has mitotic figures
Additional References