Clinicopathological Profile of Surgically Resected Renal Angiomyolipomas: A Cross-sectional Study of 31 Cases from a Tertiary Care Centre

Introduction: Although Renal Angiomyolipoma (AML) is a relatively rare entity, it is the most common benign mesenchymal kidney tumour, made up of varying amounts of thick-walled blood vessels, smooth muscle, and adipose tissue. AML occurs either sporadically or in association with Tuberous Sclerosis Complex (TSC). It is often detected incidentally during imaging, though it can present with flank pain, haematuria, or life-threatening haemorrhage, thereby posing diagnostic and therapeutic challenges. Aim: To analyse the clinicopathological features of surgically resected renal AMLs and evaluate the association between radiological and histopathological findings. Materials and Methods: This was a retrospective, crosssectional study conducted in the Department of Pathology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India, in which the clinicopathological features of surgically resected renal AMLs received between January 2014 and October 2023 were studied. Data retrieval, analysis, and manuscript preparation were carried out between December 2023 and March 2024. Clinicoradiological detailsincluding age, gender, clinical presentation, tumour size, laterality, imaging features (fat-rich or fat-poor), presence of haemorrhage, association with TSC/LAM, and type of surgical procedure were retrieved from the hospital information system of the study Institute. The data were analysed using Statistical Package for the Social Sciences (SPSS), IBM Corp, Armonk, NY), version 26.0. Categorical variables are reported as frequencies and percentages, whereas the mean (standard deviations) or medians with interquartile ranges, as appropriate, were used for continuous variables; the associations between categorical variables were analysed using the Chi-square test, where p-value <0.05 was considered to indicate statistical significance. Results: The study included a total of 31 patients, with a mean age of 48.9±16.8 years, and a mean tumour size of 10.0±6.1 cm, resulting in a female-to-male ratio of 2.4:1. Twenty-seven cases were symptomatic, while four were incidental. The major subtype was classical (24), followed by leiomyoma-like (4), epithelioid (2), and lipoma-like (1). Fat-poor AML patients who underwent surgery for Renal Cell Carcinoma (RCC) on imaging were confirmed via histopathology (epithelioid-1, leiomyomalike-3). Bleeding was observed with tumour size ≥6.0 cm (n=10 cases; p-value=0.012). TSC-associated cases (n=3) were younger (mean age-30.3 years vs sporadic-50.4 years) and had a larger mean tumour size of 16.8 cm (vs sporadic-8.8 cm). One patient had concurrent RCC. Conclusion: TSC-associated cases present at a younger age when compared to sporadic AMLs. Fat-poor AMLs can typically mimic RCC on imaging. Larger tumours are known to cause haemorrhage, particularly TSC-associated, from the rupture of pseudoaneurysms. Immunohistochemistry (IHC) for Human Melanoma Black (HMB) 45 and Smooth Muscle Actin (SMA) was useful in establishing a diagnosis in atypical AMLs.