TPA is a rare lesion occupying the uterine cavity or the cervical canal consisting of fibroid stroma and glands . Abnormal bleeding was the most common manifestation of endometrial TPA, followed by menstrual changes; Other manifestations were secondary dysmenorrhea, vaginal discharge. Some patients may even have no symptoms. There was no apparent specificity in endometrial TPA's clinical manifestations, a transvaginal ultrasound, and tumor morphology. It is easily confused with other uterine lesions. Therefore, the pathological examination was the golden standard for a definite diagnosis.
The pathogenesis of TPA is still not clear. Some scholars [9, 10] believed that adenomyomatous polyps originate from stromal progenitor cells in the endometrium, which can differentiate into smooth muscle and may be the product of long-term estrogen stimulation. Lin et al. reported a case in which a gonadotropin-releasing hormone agonist effectively reduced the size of the lesion, suggesting that the growth is dependent on the estrogen level . In this study, the average age of onset of the patients was 53.26 years, and the incidence rate was significantly higher in women >50 years old than in women <50 years old, which may be related to the long-term or continuous estrogen stimulation with little or no progesterone antagonism in this age group. Moreover, tamoxifen has been reported to exhibit a weak estrogen-like effect in postmenopausal women that increases the occurrence and recurrence rate of TPA [12, 13]. On the contrary, in this study, there was no significant difference in the recurrence rate between the different age groups after conservative surgery of TPA, and age was not a risk factor for the recurrence of TPA. This may be related to the short follow-up duration and the small sample size of the present study.
However, our findings revealed that chances of TPA occurrence and relapse were greater in postmenopausal women. The decreased estrogen level in postmenopausal women elevates follicle stimulating hormone level, leading to increased estrogen receptor expression in utero . Longacre et al. also reported that in addition to the high estrogen level in patients, the abnormal expression of estrogen receptors in the local endometrium is also associated with TPA occurrence . Postmenopausal women had a significantly higher BMI than premenopausal women in the present study. Overweight and obesity rates were also significantly greater. The BMI of postmenopausal women has been reported to be positively correlated with the estrogen level over an extended period . Weight gain and obesity result in insulin resistance and hypertension, and insulin resistance is closely linked to abnormally high estrogen levels. Therefore, obese individuals are more likely to develop TPA. In this study, 255 patients (52.25%) were overweight, and 87 patients (17.83%) were obese, supporting the above views on TPA occurrence.
Pathologically, TPA resembles adenomyosis, i.e., both conditions are characterized by abundant smooth muscle stroma and endometrial glands. TPA is reported to occur when an adenomyoma breaks into the endometrial cavity, which is why TPA may be considered under the category of uterine adenomyosis . Although a link between TPA and adenomyosis has been established, there are some differences between the two pathologies. In adenomyosis specimens, the endometrial glands and stroma are divided into islands by the smooth muscle within the myometrium. Moreover, the uterine smooth muscle tissue in adenomyosis is morphologically different from that in TPA. However, polypoid adenomyomas are often accompanied by adenomyosis, and the two pathologies may be similar in histogenesis . In this study, we found that most patients had a history of pregnancy. Patients with gravidity >3 and parity >2 were more likely to develop TPA, and gravidity >3 and parity >2 were independent risk factors for TPA. Chances of relapse were greater in patients with gravidity >3. Besides, the rate of adenomyosis and endometriosis in the TPA group was higher than that in the normal group. All these results suggest that surgery of the uterine cavity and endometrial injury may be related to the occurrence of TPA .
Among the 360 TPA patients who underwent conservative surgery,hysteroscopic electrotomy, curettage, and polyp clamp, there were 32 cases (8.89%) of relapse. Parity, menopausal status, and surgery method were related to TPA recurrence, and gravidity >3, menopause, curettage, and polyp clamp were independent risk factors for TPA recurrence. This supported the link between elevated levels of estrogen and its receptors and endometrial damage. When planning the surgery, it is important to consider the unique pathogenesis and pathological characteristics of TPA. Because the lesion cannot be directly targeted by curettage and polyp clamp and because the texture of adenomyomatous polyps is arduous and the base is broad, the postoperative residual rate of lesions is high. Hysteroscopy can altogether remove the directly visible lesion, and other suspected endometrial lesions can be biopsied simultaneously, with minimal trauma.
In this study, 332 patients who underwent hysteroscopic electrotomy were followed up successfully; only eight patients exhibited recurrence without any malignant change, indicating that hysteroscopic electrotomy is a safe and effective treatment method. Hysteroscopic resection of directly visible lesion tissues could reduce trauma and preserve fertility, yielding a definite curative effect . Therefore, a four-step hysteroscopic resection of the lesion is preferred: (1) complete resection of the lesion from the root pedicle; (2) removal of 0.2–0.5 cm of the endometrial tissue around the root pedicle; (3) ensuring that the myometrium below the root pedicle is about 0.3 cm deep; (4) multi-point biopsy of the endometrium at other locations of the uterine cavity .
The main strength of this study is that a large number of patients with TPA and normal endometrium were included. Moreover, 360 cases of TPA were followed up for 22–77 months. Besides, patients who underwent conservative surgery were from the same sample group, reducing bias and yielding more accurate results.
However, this study also has some unavoidable limitations due to its retrospective design. First, we could not assess all variables potentially associated with the occurrence and recurrence of TPA in this single study. Furthermore, the inclusion of cases involving only one hospital might have reduced the external validity of the results, and further prospective studies with a larger sample size in a broader context are needed.