Cervical endometriosis associated with malignant pleural mesothelioma mimicking cervical cancer—Occam’s razor or the 'third man'

Objective To illustrate pitfalls in the diagnosis of endometriosis and cervical cancer. Design Case report. Setting University hospital, department of obstetrics and gynecology. Patient(s) A 45-year-old woman with menorrhagia, pelvic mass, right-sided hydronephrosis, and unexplained weight loss. Intervention(s) Cervical biopsies were suggestive of cervical endometriosis. Laparoscopy confirmed endometriosis. Associated pleural effusion, without cytologic signs of malignancy, was interpreted as caused by thoracic endometriosis. The patient had a transabdominal hysterectomy and unilateral salpingo-oophorectomy. Histopathologic examination confirmed endometriosis and revealed a residual tubo-ovarian abscess. After surgery, the patient developed spontaneous seropneumothorax. Pleural biopsies revealed a well-differentiated epithelial malignant pleural mesothelioma. The patient underwent hypofractionated radiation of drain sites. She is now observed in our outpatient clinic. Main Outcome Measure(s) Steps to the correct diagnosis. Result(s) The patient had an association of cervical and pelvic endometriosis, residual tubo-ovarian abscess, and malignant pleural mesothelioma. Conclusion(s) Usually, the simplest diagnosis explaining a complex of symptoms and clinical and diagnostic findings is the one most likely to be correct. This is an application of Occam's razor to medicine. Our case illustrates that occasionally the simplest and therefore most probable diagnosis can be wrong, and on these occasions one should consider a "third man."