This video presents a pathology case study of a pedunculated lesion in the axilla, initially thought to be an inflamed and painful skin tag. Histological examination reveals it to be an intradermal nevus, characterized by benign melanocyte nests showing maturation with depth. The "twist" of the case is the discovery of significant reactive changes within and around the nevus, including dilated blood vessels, epidermal hyperplasia, and replacement of nevus tissue by scar and granulation tissue. Crucially, the presence of both hair shafts and refractile, polarizing synthetic filamentous structures at the base of the lesion indicates that the patient attempted to self-strangulate the nevus, leading to the clinical symptoms of inflammation, pain, and ischemic changes. This highlights the importance of pathological findings in uncovering patient actions not always disclosed clinically.
Understanding a Partially Strangulated Intradermal Nevus
0:00 Clinical Presentation: The video introduces a pedunculated lesion in the axilla, clinically suspected to be an inflamed and painful skin tag, but revealed to be a nevus.
0:28 Pedunculated Lesion Morphology: Pedunculated or polyploid lesions often display a nodule almost completely surrounded by epidermis, which is a helpful diagnostic clue for beginners in pathology.
0:46 Benign Nevus Features: The dermis contains nests of melanocytes that show maturation (getting smaller and more single-celled) as they go deeper, indicating a benign intradermal nevus.
1:27 Reactive Inflammatory Changes: The nevus exhibits dilated blood and/or lymphatic vessels, reactive epidermal hyperplasia (pseudoepitheliomatous hyperplasia), and thickening of the corneal and granular layers (keratinization).
1:58 Tissue Degeneration and Replacement: The nevus tissue is being replaced by scar and granulation tissue, characterized by reactive myofibroblasts, lymphocytes, eosinophils, and collagen bundles, explaining the patient's pain.
2:40 The Pathological "Twist" - Foreign Material: Examination of the lesion's stalk reveals multiple hair shafts (keratin, melanin, squished nuclei) alongside thin, elongated, refractile, and polarizing filamentous structures (synthetic yarn/string).
4:08 Patient's Attempted Self-Treatment: The presence of both hair and synthetic fibers strongly suggests the patient attempted to strangulate the lesion, likely mistaking it for a skin tag, to make it fall off.
4:56 Clinical Implications: This self-strangulation led to ulceration, fibrin deposition, degeneration, dilated vessels, and ultimately ischemia and potential infarction of the lesion, causing the sudden pain, inflammation, and altered clinical appearance.
5:31 Conclusion: This case serves as an excellent example of a partially strangulated polyploid intradermal nevus, illustrating how pathological examination can uncover the cause of unusual clinical presentations.