Lower Limb Lymphoedema as an Unusual Initial Presentation of Metastatic Prostate Cancer.

Secondary lymphoedema in malignancy typically arises as a result of its treatment. In rare cases, it can be a manifestation related directly to the metastatic disease, through lymphatic obstruction or infiltration. Lymphoedema as the initial presentation of advanced prostate cancer has been described only in isolated case reports. We present an unusual case of a 66-year-old obese male with type 2 diabetes mellitus and hypertension, who presented with a seven-year history of progressive bilateral lower limb swelling, repeatedly diagnosed as cellulitis secondary to idiopathic lymphoedema. He had received multiple courses of antibiotics for recurrent Group G Streptococcal cellulitis. On admission, he was febrile with malodorous, oedematous lower limbs displaying papillomatosis and fibrotic, cobblestone-like plaques. Imaging revealed widespread lymphadenopathy, destructive vertebral lesions, and features concerning for metastatic malignancy. A markedly elevated prostate-specific antigen (130 μg/L) alongside MRI findings of a prostate imaging reporting and data system, category 5 (PI-RADS 5) lesion in the prostate, pelvic nodal disease, and lytic bony metastases suggested a radiological diagnosis of metastatic prostate cancer. The patient was commenced on androgen deprivation therapy following multidisciplinary team discussion and unsuitability for prostate biopsy. To the best of our knowledge, only one case of unilateral lower limb lymphoedema as the initial presentation of metastatic prostate cancer has been reported. This case demonstrates a plausible association between bilateral lower limb lymphoedema and metastatic prostate cancer. We discuss mechanisms of lymphoedema development in malignancy, emphasise the importance of considering underlying malignancy in unexplained or refractory lymphoedema and express the need for comprehensive assessments in unexplained secondary lymphoedema to help mitigate the impact of cognitive biases.