Boyd and McCluggage reported histologic changes that occur in leiomyomas of women being treated with progesterone compounds. The changes may be mistaken for leiomyosarcoma or a smooth muscle tumor of uncertain malignant potential (STUMP). The authors are from Belfast Health and Socia Care Trust in Belfast.


Patient selection: women with leiomyoma and a history of recent or current therapy with a progesterone compound


Histologic features that may be confused with a malignancy:

(1) areas of necrosis (usually infarct-type but occasionally resembling tumor necrosis)

(2) mitotic activity in smooth muscle cells adjacent to the areas of necrosis

(3) increased cellularity


Key diagnostic features:

(1) history of progesterone therapy

(2) lack of true nuclear atypia

(3) low mitotic activity in the leiomyoma away from areas of necrosis


Additional features may include:

(1) cytoplasmic eosinophilia

(2) nuclear pyknosis

(3) epithelioid morphology

(4) stromal edema

(5) hemorrhage

(6) myxoid change

(7) lymphocytic infiltrate (granular cytoplasma, CD56 positive)


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