European Society of Toxicologic Pathology (ESTP)
    European Society of Toxicologic Pathology
Guess What! - ESTP Case 6

The case is from a 118-week old Wistar rat. Both ovaries were normal at necropsy.

Click on the images below for a larger view.
Case 6, Fig. 1
Fig. 1: H&E, x2.5
Case 6, Fig. 2
Fig. 2: H&E, x5
Case 6, Fig. 3
Fig. 3: H&E, x10
Case 6, Fig. 4
Fig. 4: H&E, x20

Morphologic Description

The alteration is characterized by multifocal nodular lesions in the ovary, which are surrounded by a cystic space of variable size. The nodules consist of highly cellular aggregates of tubular structures or cords, lined by a cuboidal to columnar epithelium. The basophilic cells show a high nuclear:cytoplasmic ratio. Although stromal cells are not prominent, a few luteinized cells can be recognized. The histogenic origin of this lesion is the surface epithelium of the ovary.

Proposed Diagnosis
Tubulostromal hyperplasia

Differential Diagnoses and Discussion

General comment: Since the lesion was without cellular atypia and the diameter of the largest nodule was smaller or equal to the size of a corpus luteum, it was considered to represent a hyperplasia rather than a tumor. The RITA-data base panel decision was 8:3 for hyperplasia : adenoma.

Cystadenoma was considered as an alternative diagnosis by several contributing participants. Although stromal cells are not prominent in the present case, a few luteinized cells could be recognized. In addition, the growth pattern is tubular and not papillary.

Hyperplasia, cystic-papillary the lesion was without cellular atypia and the diameter of the largest nodule was smaller or equal to the size of a corpus luteum.

Granulosa cell tumor shows a different cellular morphology (round to oval) and no tubular growth pattern.

Dysgerminoma-germ cell tumor the present lesion shows only well-differentiated cells in organized structures.

Click on the images below for a larger view.
Case 6, Fig. 5
Fig. 5: H&E, x20
Case 6, Fig. 6
Fig. 6: H&E, x20
Case 6, Fig. 7
Fig. 7: H&E, x40

References

  • Alison RH, Morgan KT, Haseman JK, Boorman GA (1987) Morphology and classification of ovarian neoplasms in F344 rats and (C57BL/6 x C3H)F1 mice. J Natl Cancer Inst 78: 1229-1243
  • Alison RH, Morgan KT, Montgomery CA (1990) Ovary. In: Boorman GA, Eustis SL, Elwell MR, Montgomery CA, Jr, MacKenzie WF (eds) Pathology of the Fischer rat. Reference and atlas. Academic Press, San Diego New York London, pp 429-442
  • Gregson RL, Lewis DJ, Abbott DP (1984) Spontaneous ovarian neoplasms of the laboratory rat. Vet Pathol 21: 292-299
  • Lewis DJ (1987) Ovarian neoplasia in the Sprague-Dawley rat. Environ Health Perspect 73: 77-90