A hint for abnormal thoracic shadow: look behind the heart

Discussion

PBML is a rare disease that develops months to years after a diagnosis of uterine myoma with a history of myomectomy or hysterectomy. The prevalence is highest among women in the late childbearing age, with a mean age of 46 years [1]. Various theories have been proposed to explain the possible mechanisms of tumour spread. These include haematogenous or lymphatic spread of uterine leiomyoma, in situ proliferation of smooth muscle induced by hormonal stimulation, metastasis of low-grade uterine leiomyosarcoma, peritoneal seeding after surgery for uterine leiomyoma and metaplastic transformation [2]. Rader et al. [3] reported a case of uterine leiomyoma that caused massive lower gastrointestinal haemorrhage and required exploratory laparotomy, hysterectomy, and bowel resection. By contrast, Abell and Littler [4] described a case of histologically benign pelvic and para-aortic lymph node metastases that resulted from fragments of leiomyoma that had entered dilated lymphatic channels at the time of endometrial curettage. Nishiwaki et al. [5] reported a case of intravenous leiomyomatosis that originated from the uterus and extended into the right pulmonary artery. These cases highlight the theory of haematogenous and lymphatic spread that may result in extraperitoneal cavity involvement, such as lung metastasis.

Commonly, the diagnosis of PBML is incidental to routine imaging of an asymptomatic patient, while some patients present with dyspnoea and respiratory distress. Despite the benign nature of the tumour, there are cases with rapid progression leading to local compressive effects such as the narrowing of the right main bronchus that is seen in our case [6]. The most common radiological finding in PBML is described as multiple solid nodules in the lungs. Other rare features include a solitary nodule, small miliary nodules, or mediastinal mass [7]. It is important to consider leiomyosarcoma as a potential diagnosis in cases with rapid tumour progression. An ¹⁸F-FDG-PET scan is useful to evaluate the possibility of aggressive malignant tumour [8]. Although a lung biopsy may indicate a benign nature, it is important to note that leiomyosarcoma can exhibit a heterogenous nature. Therefore, relying solely on the results of a lung biopsy may not provide a comprehensive assessment of the tumour's behaviour. VATS is often considered the gold standard for obtaining a definitive diagnosis [9]. As our patient refuses VATS, a multidisciplinary approach involving a team of respiratory physicians, oncologists, radiologists and pathologists may be necessary to collectively diagnose and decide further management.

There is no standard clinical practice guideline for the treatment of this disease. Main modalities of treatment include close observation, surgical resection and/or hormonal therapy, such as progestin inhibitors and luteinising hormone-releasing hormone analogues [10]. The treatment of PBML varies depending on the symptoms and compressive effect of the tumour. Surgical resection has been the mainstay of treatment for tumours with mass effect [11]. Surprisingly, a growing number of reports indicate that some tumours continue to progress despite surgical resection, indicating that hormonal therapy might be a vital adjunct to treatment [11, 12]. The presence of oestrogen and progesterone receptors in these tumours support their origin from uterine smooth muscle, and more importantly supports the use of hormonal therapy, especially in unresectable metastatic disease [13]. Progesterone and selective oestrogen receptor modulation therapy such as tamoxifen has shown regression of tumour size due to its ability to suppress the hypothalamic–pituitary–gonadal axis and reduce ovarian oestrogen production [14].