This video presents a pathology case study of a 2 cm inguinal mass in a 50-year-old man, diagnosed as Cellular Angiofibroma (CA). The presenter reviews the microscopic findings, which include bland spindle cells, abundant wavy ("ropey") collagen bundles (referred to as the "ramen noodle sign"), and prominent vasculature, often mimicking a Solitary Fibrous Tumor (SFT). The discussion emphasizes that CA is a benign entity closely related to Spindle Cell Lipoma (SCL), sharing features like CD34 positivity and a key genetic alteration: the loss of RB1 protein expression. The video highlights the importance of distinguishing CA/SCL from SFT using immunohistochemical markers (STAT6 for SFT, RB1 loss for CA/SCL), although all three entities are typically cured by simple excision in benign presentations.
Cellular Angiofibroma: Case Review and Key Pathological Features
0:13 Case Presentation: The case involves a 50-year-old man presenting with a 2-centimeter inguinal mass.
0:34 Microscopic Findings and Differential Diagnosis (DDx): Microscopic examination reveals a vascular lesion composed of bland spindle cells with no significant mitotic activity, set in an edematous or dense stroma containing trapped adipose tissue. The DDx proposed was excellent, including Cellular Angiofibroma (CA), fat-poor Spindle Cell Lipoma (SCL), and Solitary Fibrous Tumor (SFT).
1:39 "Ramen Noodle Sign": The stromal collagen is described as "ropey" and "wavy," a feature (sometimes called the "ramen noodle sign") that often suggests a neural tumor but is frequently more pronounced in fibroblastic entities like SCL and CA.
2:24 Confirmed Diagnosis and Relation to SCL: The final diagnosis is Cellular Angiofibroma. CA is considered closely related to SCL, sharing many overlapping features and falling within a family of benign tumors.
3:01 Location and Vascularity: CA commonly occurs in the genital region. As its name implies, it has numerous vessels, often displaying an ectatic, branching, or staghorn pattern which can cause confusion with SFT.
3:14 Key IHC Markers: CA, SCL, and SFT are typically CD34 positive. CA can also sometimes express Actin and Desmin.
3:32 Cytologic Feature β Nuclear Palisading: A helpful finding in CA and SCL is the subtle "packeting" or parallel arrays (palisading) of bland spindle cell nuclei, forming small clumps separated by hypocellular zones.
4:33 Genetic Marker (RB1 Loss): The most recently described, helpful marker is the loss of the Retinoblastoma gene (RB1) protein expression, detected via immunostain (loss of nuclear staining) or FISH (monosomy). This loss is seen in the majority of CA and SCL cases.
5:47 Clinical Takeaway: The clinical distinction between CA and SCL is usually not critical, as both are benign and cured by simple excision. However, differentiating them from SFT is sometimes necessary; SFT is STAT6 positive and retains RB1 expression, while CA and SCL are STAT6 negative and show RB1 loss.
6:38 Nomenclature Complexity: The presenter notes the difficulty in soft tissue pathology due to the proliferation of similar-sounding tumor names (e.g., numerous entities containing "angiofibroma").