AML – a rare variant
Reviewed by Arun K Sharma

With the increasing number of CT and ultrasound scans performed in hospital practice more and more incidental angiomyolipomas (AML) are being picked up, some of which are asymptomatic and may not bother patients at all. This study comes from the Royal Free Hospital / North London Renal Group. The epithelioid variant of angiomyolipoma belongs to the perivascular epithelioid cell family of tumours. EAMLs are rare renal tumours which, although classified as benign, can frequently display malignant behaviour and poor outcomes. EAML can only be distinguished from benign AML by microscopic phenotypic analysis. Histologically, they display low fat-cell content, presence of epithelioid cells in more than 80% of the tumour, and cytologic atypia. Typical morphology can resemble high-grade RCC with sarcomatoid differentiation. Both EAMLs and classical AMLs can exhibit positivity for HMB-45 and Melan-A expression, vimentin, desmin and other smooth muscle cell markers, so immunohistochemistry cannot be used to reliably distinguish between the two. No clinical practice guidelines exist for the management of EAML. The potential malignant behaviour of these tumours can be suspected on biopsy and surgery is warranted. Although these renal tumours are rare, there have been some studies that explore the outcomes of patients with EAMLs. The clinical implications of EAML have been mixed. Faraji et al. reviewed 40 case reports and series of EAML, totalling 69 cases. Adverse outcomes (metastasis or death due to disease) were found in 40% of patients. Nese et al. analysed 41 cases of kidney EAML, and found a 17% rate of recurrence and 49% metastasis rate, with 33% of patients dying of EAML. In the current study of five cases presented, three died from disease progression, which highlights the difficulty in counselling and treatment. No guidelines exist on systemic treatment for metastatic EAML. The lack of studies means that uncertainty persists regarding the systemic treatment of these patients. The development of a new form of immune modulation via checkpoint inhibition, has changed the management of metastatic RCC, and some drugs are now considered first-line treatment for intermediate and high-risk cases. Whether these drugs are of benefit in EAML remains to be seen. The risk of tumour progression is significant and a high index of caution should be taken. While no specific guidelines on the management of EAMLs are available, the best approach seems to be surgical excision and careful follow-up.

Epitheloid angiomyolipomas of the kidney: rare renal tumors associated with poor prognoses.
Aquilina J, Neves J, El-Sheikh S, et al.
UROLOGY
2023;176:102-5.