cne21th

Criteria and diagnostic terms for uterine smooth muscle tumors (adapted from the work of Richard Kempson )

Coagulative necrosis

Mitotic count per 10 HPF

Atypia

Diagnosis

Present

Greater than 10

Moderate to severe (focal or diffuse)

Leiomyosarcoma

None to mild

Leiomyosarcoma

Equal or less than 10

Moderate to severe (focal or diffuse)

Leiomyosarcoma

None to mild

STUMP (1)

Absent

Greater than 10

Moderate to severe, focal

Leiomyosarcoma

Moderate to severe diffuse

STUMP (2)

None to mild

Mitotically active leiomyoma (up to 15 mitoses/10 HPF are allowed)

Equal or less than 10

Moderate to severe, focal

STUMP (3)

Moderate to severe diffuse

Leiomyoma (4)

None to mild

Leiomyoma

(1) Of the three tumors here placed in the STUMP category, this is the one most likely to behave in a malignant fashion. Actually, it is regarded as a probable leiomyosarcoma in Kempson's scheme. The alternative possibility of an infarction in a leiomyoma due to torsion or other factors should be considered.
(2) In Kempson's scheme, this is designated as STUMP if the mitotic activity is higher than 15.
(3) This is referred to as "atypical leiomyoma with low risk of recurrence" in Kempson's scheme.
(4) This is designated as "leiomyoma with limited experience" in Kempson's scheme.