This video presents a detailed dermatopathology case study of a skin biopsy from an ulcerated nodule, initially showing reactive epithelial changes that closely mimic squamous cell carcinoma (pseudoepitheliomatous hyperplasia). Microscopic examination of the surface crust reveals fibrin and abundant neutrophils, typical of ulceration. The crucial diagnostic feature, however, is the presence of perfectly round, thick-walled, pigmented fungal organisms embedded in the tissue—known as "sclerotic bodies," "Medlar bodies," or "copper pennies." This classic finding establishes the diagnosis of chromoblastomycosis, an infectious process caused by dematiaceous (pigmented) fungi, typically acquired via traumatic inoculation. The case highlights the need to differentiate reactive hyperplasia from malignancy by identifying associated infectious agents and inflammatory patterns.
Dermatopathology Case: Distinguishing Reactive Hyperplasia from Carcinoma
0:05 Case Presentation: The biopsy is from an ulcerated, pedunculated nodule (likely from the leg). The surface is heavily ulcerated and covered by a thick crust.
0:19 Ulceration Histology: The surface crust is histologically composed of bright pink fibrin and numerous dark-specked neutrophils, defining a scab/crust. Incidental purple bacterial colonies are also noted, which are often normal flora on an ulcer.
1:18 Mimicking Cancer: Deeper sections show the epidermis is thick and growing downward, mimicking the appearance of Squamous Cell Carcinoma (SCC).
1:40 Reactive Clue: The tissue is identified as reactive pseudoepitheliomatous hyperplasia (PCEH). A key clue distinguishing this from true SCC is the presence of aggregates or pustules filled with neutrophils trapped within the glassy squamous epithelium. This pattern prompts a search for infectious or reactive causes.
2:44 Diagnostic Finding: Identification of perfectly round, thick-walled, brown/pigmented structures known as sclerotic bodies, Medlar bodies, or colloquially, "copper pennies." These are melanin-producing pigmented fungi.
3:35 Final Diagnosis: The presence of these sclerotic bodies confirms the diagnosis of Chromoblastomycosis, a characteristic pattern of infection caused by dematiaceous (pigmented) fungi.
3:54 Etiology: Chromoblastomycosis is typically acquired via traumatic inoculation (e.g., a penetrating injury from contaminated material like wood or sticks) in damp, warm environments.
5:51 Search Strategy: The fungal organisms are often found embedded in the dermis and are frequently associated with collections of neutrophils or granulomas (histiocytes).
5:56 Staining Takeaway: The fungal bodies are clearly visible on standard Hematoxylin and Eosin (H&E) staining due to their inherent brown pigmentation and thick walls, making special stains (like PAS or GMS) often unnecessary for diagnosis.
4:50 Related Differentials: If pigmented hyphae (instead of round bodies) are seen, the infection is classified as Phaeohyphomycosis. If non-pigmented fungi cause the reactive epithelial changes, Blastomycosis must be considered.