This pathology case review focuses on a 3 cm renal mass found in a 45-year-old female, leading to the diagnosis of Angiomyolipoma (AML). AML is characterized by three main components: mature adipose tissue, thick-walled vessels, and an atypical smooth muscle component. The video emphasizes the distinctive morphological features of the tumor, particularly the smooth muscle cells exhibiting a pale, granular, or "chunky pink" cytoplasm, which is highly characteristic of AML. Categorized within the Perivascular Epithelioid Cell Tumor (PEComa) family, AML displays a unique "myo-melanocytic" immunophenotype, co-expressing both muscle markers (SMA, desmin) and melanocytic markers (HMB-45, Mart-1). The discussion highlights the potential for misdiagnosis (e.g., confusing it with liposarcoma) and notes its association with Tuberous Sclerosis, stressing the importance of recognizing its distinct histological appearance.
Summarizing Case #3: Angiomyolipoma of the Kidney
0:00 Case Introduction: The case involves a 45-year-old female patient presenting with a 3 cm mass adjacent to the kidney.
0:26 Gross Morphology: The mass is well-circumscribed and located right beneath the capsule of the kidney.
0:52 Tissue Components: Histological analysis reveals two main components: mature adipose tissue (fat) and a component of pink, spindle-shaped cells, which are identified as muscle tissue.
1:52 Vascular Pattern: A crucial finding is the presence of thick-walled vessels with associated smooth muscle bundles seemingly growing directly off the vessel walls, a characteristic feature.
2:08 Diagnosis and Classification: These features confirm the diagnosis of Angiomyolipoma (AML). AML belongs to the family of Perivascular Epithelioid Cell Tumors (PEComas).
3:29 Unique Cytoplasm (Key Takeaway): The smooth muscle component in AML is distinctive. Unlike regular smooth muscle, it possesses a granular, pale, "chunky pink" cytoplasm, which is considered highly characteristic of AML and often seen in other PEComas.
4:25 Unusual Immunophenotype: AML expresses a strange "myo-melanocytic" differentiation, co-expressing both:
Melanocytic markers (HMB-45, Mart-1 positive).
Muscle markers (SMA, calponin, desmin positive).
AML is often negative for S100 and SOX10.
6:03 Associated Syndrome: The tumor sometimes occurs in patients with Tuberous Sclerosis (TSC), although sporadic cases are also common.
6:34 Clinical Context: Due to their large size and fatty component, especially when retroperitoneal, AMLs can be easily confused with well-differentiated liposarcomas, emphasizing the need for careful microscopic examination and marker testing.