Uterine smooth muscle tumor of uncertain malignant potential (STUMP) ABOUT a CASE.

This is a 53-year-old patient, mother of a child born vaginally, with no history of oral contraception, menopausal for 2 years, history of a sister operated on for uterine myoma, presenting with postmenopausal metrorrhagia and, feeling of heaviness, with no urinary or digestive disorders. On clinical examination: enlarged uterus reaching midway to the umbilicus. On pelvic MRI: MRI appearance of a large corporofundial myometrial mass lateralized to the left, suggestive of a hypercellular leiomyoma in edematous degeneration, although a leiomyosarcoma could not be ruled out ( Fig. 1 , Fig. 2 ). The patient underwent hysterectomy ( Fig. 3 ). Anatomopathological study: large, poorly limited, whitish renitened endocavitary mass measuring 16 cm in diameter ( Fig. 4 ), This mass shows a highly cellular, spindle-cell tumor proliferation consisting of elongated cells with large or medium-sized, rounded or elongated nuclei, irregular chromatin, often with one or more small nucleoli, and poorly defined eosinophilic or clear cytoplasm. Mitoses are of the order of 7 to 8 per 10 fields at high magnification. These cells are arranged in bundles, crossed at right angles and separated by a discrete collagenous fibrosis with numerous, congestive capillaries and a few inflammatory cells, all of this corresponding histologically with a uterin smooth muscle tumor of uncertain malignancy (STUMP), associated with florid adenomyosis and moderate glandular hyperplasia of the endometrium ( Fig. 4 ). On immunohistochemical study: the proliferation marker antiKi67 was estimated at < 2   %, which ruled out sarcomatous pathology. The extension workup, performed with CT-PET, revealed no secondary localization. The patient was referred to the oncology department for surveillance. Fig. 1 MRI sagittal section image showing a myometrial mass. Fig. 1 Fig. 2 MRI image showing cross-sectional myometrial mass. Fig. 2 Fig. 3 Inter-adnexal hysterectomy part. Fig. 3 Fig. 4 Dissection piece showing a whitish endocavitary mass measuring 16 cm in diameter. Fig. 4 MRI sagittal section image showing a myometrial mass. MRI image showing cross-sectional myometrial mass. Inter-adnexal hysterectomy part. Dissection piece showing a whitish endocavitary mass measuring 16 cm in diameter.

CHERKAOUI AMAL : writing the paper. ATFI FADWA: writing the paper. Gotni aicha correction the paper. HOUSSINE BOUFETAL: correction of the paper. SAKHER MAHDAOUI: correction of the paper. NAIMA SAMOUH: correction of the paper.

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An uterine smooth muscle tumor that cannot be histologically diagnosed as benign or malignant should be termed a “smooth muscle tumor of uncertain malignant potential” (STUMP). They represent a heterogeneous group of rare tumors that have been the subject of only a few published studies, some of which lack clinicopathological detail and follow-up data. More recently, it has been suggested that immunohistochemical staining may be useful in the diagnosis of STUMPs. We report the case of a patient who underwent hysterectomy for suspected uterine sarcoma and whose pathological examination revealed a STUMP tumor. This case report was prepared in accordance with the SCARE guidelines 2023 [ 22 ].

The clinical manifestations of STUMP are non-specific, frequently similar to those of leiomyomas - namely metrorrhagia, pelvic mass and pelvic pain - but also secondary symptoms of compression phenomena or anaemia [ 8 ]. In our study, the main clinical manifestation was post-menopausal metrorrhagia.

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CHERKAOUI AMAL.

Generally, STUMP diagnosis is decided after myomectomy or hysterectomy according to three histological criteria of the Stanford. If the tumor does not meet criteria for leiomyosarcoma, and has combinations of Stanford's criteria, STUMP diagnosis is accurate [ 20 ]. Hysterectomy is currently considered the gold standard of treatment. It is particularly recommended for women who are menopausal and for whom fertility maintenance is not a major issue. Patients who desire pregnancy should be informed about potential morbidity and mortality of tumor. On the other hand, the choice between myomectomy and hysterectomy represents a real problem in the management of STUMP in young women, reconciling the risk of recurrence with fertility preservation [ 18 ]. Recurrence rates reported in the literature range from 7 % to 27 %, with a total recurrence rate of 11 % [ 3 , 4 , 5 ]. Treatment options for recurrence in addition to surgery include adjuvant chemotherapy, radiotherapy, and progestins GnRH analogs [ 19 ].

Uterine STUMP represents a therapeutic dilemma, Is this due to diagnostic difficulties, variability in clinical behavior and inadequate therapeutic options, but above all to the fact that diagnosis are uneventful after tumor resection and further observational data would be needed to reach a consensus on management balancing the indolent clinical course and malignant, even lethal, potential. A multidisciplinary approach is mandatory, and we encourage the collection of larger series to obtain as much data as possible on this rare entity. A future prospect could be to identify the molecular basis of STUMP using molecular biology techniques. The identification of key genes directly involved in the carcinogenesis of STUMP could suggest new opportunities in the management of the disease and provide additional information for understanding the process of carcinogenesis.

Preoperative STUMP diagnosis or differentiation from leiomyoma-leiomyosarcoma with imaging modalities is not easy . Ultrasound is a routine diagnostic tool for uterine tumors. However, one study showed that ultrasound could not differentiate STUMP from similar tumors. No significant correlation was observed between ultrasound findings and pathological features of STUMP, such as cellular atypia, necrosis and mitotic figs. [ 9 ]. Thanks to its superior soft-tissue resolution, MRI is an ideal imaging tool for the evaluation of suspicious uterine lesions. One study showed that contrast-enhanced MRI (CE-MRI) provided accurate information for the preoperative differentiation of STUMP or leiomyosarcoma from leiomyoma [ 10 ]. In a retrospective study, an MRI classification system based on three elements - T2-weighted imaging, diffusion-weighted imaging and apparent diffusion coefficient values - was designed to assess the possibility of preoperatively differentiating leiomyoma and its variants or STUMP [ 11 ].

The spectrum of uterine smooth muscle tumors varies from the benign variants represented by leiomyoma to the malignant equivalent, leiomyosarcoma [ [4] , [5] , [6] ]. A similar tumor that cannot be diagnosed with certainty as benign or malignant is called STUMP. It is the evolution of this category that gives it its ultimate biological potential [ 7 ].

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Numerous immunohistochemical markers have been studied in uterine smooth muscle tumors, and these have been found useful in differentiating problematic tumors or those that are difficult to diagnose. Tumor expression of various markers was also assessed to determine possible prognostic factors. Several studies have noted that progesterone receptor (PR) and estrogen receptor (ER) expression is frequently present in STUMP and leiomyoma, but much less frequently in leiomyosarcoma [ 12 , 13 , 14 ]. One study concluded that the combination of high PR expression and low p53 expression could exclude the diagnosis of SLM [ 13 ]. Ki-67 is a marker of cell proliferation. Several immunohistochemical studies have observed high levels of Ki-67 in LMS, but it was markedly less frequent or weakly positive in STUMP and LM [ 12 , 14 , 15 , 16 ]. In our study, the Ki67 proliferation marker was estimated to be <2 %, and therefore negative. Kanayama et al. reported that p16 expression was present in 76.4 % of leiomyosarcomas, 38.4 % of STUMPs and 10.3 % of leiomyomas [ 17 ]. Other studies have also reported similar results [ 14 , 15 ]. Several studies observed strong p53 expression in SMLs but only weakly positive or negative expression in STUMPs and LMs. [ 12 , 13 , 15 , 21 ]. D'Angelo and Prat described the following criteria for STUMP: tumor necrosis in typical leiomyoa; necrosis and ≥10 mitosis/10 HPF or remarkable diffuse atypia; remarkable diffuse or focal atypia and borderline mitosis; and hardly classified necrosis.

STUMP is a rare pathology affecting around 0.01 % of patients treated by myomectomy or hysterectomy [ 1 ]. Current theories regard this lesion category as a transitional phase between a leiomyoma and a leiomyosarcoma, or as an undiagnosed low-grade leiomyosarcoma [ 2 ]. This pathology is diagnosed more frequently in women in their fertile years, with an average age of 44 [ 3 ]. Symptomatology is frequently similar to that of leiomyomas - metrorrhagia, mass and pelvic pain. MRI is an ideal imaging tool for the evaluation of suspicious uterine lesions, but confirmation is based on anatomopathological examination and is uneventful after tumor resection [ 21 ]. Although considered to have a low malignant potential, these tumors have the capacity to recur and metastasize. A future prospect could be to identify the molecular basis of STUMP using molecular biology techniques.

The authors declare that they have no conflict of interest.