["STUMP" (smooth muscle tumour of uncertain malignant potential), a tumour of the uterus in pregnancy--a diagnostic and therapeutic challenge].

We present the case of a preterm birth in the 27 (th) week of gestation, probably due to a chorionamnionitis, with the coincidental finding of a STUMP (smooth muscle tumour of uncertain malignant potential). The STUMP is a rare tumour entity characterised by smooth muscle cells which is difficult to classify by means of histology. The WHO classification of mesenchymal tumours allocates STUMP as an intermediate tumour between a benign leiomyoma and a malignant leiomyosarcoma. If histological criteria of malignancy are not fulfilled because the type of necrosis is in doubt or the interpretation of mitotic figures is ambiguous and the tumour cannot reliably be classified as a leiomyoma, it is classified as a STUMP. Compared to malignant leiomyosarcoma, STUMP has a superior prognosis, but the biological potential of the tumour remains unclear; lymphogenic and haematogenic dissemination seems possible even after a long period of time. STUMP represents a challenge in diagnosis and treatment recommendations. We present the first description of a case of STUMP during pregnancy, raising the question of whether the histological finding in tumours of the uterus during pregnancy are important.