This video documents a dermatopathology teaching session at UAMS, led by a fellow nearing the end of their training. The session involves reviewing several challenging and educational skin biopsy cases, focusing on diagnostic features, differential diagnoses, and key pathological findings under the microscope. Cases discussed include a trichoepithelioma, a basal cell carcinoma with pylomatrical differentiation (initially raising concern for Merkel cell carcinoma), a potential malignant hydradenoma or aggressive digital papillary adenocarcinoma, a pending malignant T-cell lymphoma, a palisaded encapsulated neuroma, a proliferating pilar tumor, and a Kaposi's sarcoma. The discussion highlights the importance of distinguishing benign follicular tumors from basal cell carcinoma, the critical need to rule out Merkel cell carcinoma when suspected, the aggressive potential of certain adnexal tumors on the digits despite bland cytology, and the overlapping features often seen in follicular neoplasms.
Dermatopathology Teaching Session: Challenging Cases and Key Diagnoses
0:00 Introduction: The video introduces a dermatopathology teaching session at UAMS, led by a fellow.
Key Features: Characterized by painful, well-formed papillary desmoplastic bodies.
Distinction: Differentiated from basal cell carcinoma (BCC) by the presence of a thick, dense cellular stroma that condenses to form papillary signals.
1:16 Case 2: Basal Cell Carcinoma with Pylomatrical Features:
Initial Concern: A resident initially considered Merkel cell carcinoma due to blue, large nuclei and fine chromatin.
Clinical Importance: Missing a Merkel cell carcinoma is critical, as approximately 50% can metastasize and cause mortality, compared to about 20% for melanoma.
Final Diagnosis: Re-evaluation revealed basal cell carcinoma with pylomatrical differentiation/features, identified by abrupt keratinization, clefting, and compensatory features, explaining the initially concerning blue appearance.
Key Takeaway: Blue cells from a polymetricoma can mimic Merkel cell carcinoma, emphasizing the need for careful differentiation.
3:22 Case 3: Malignant Hydradenoma / Aggressive Digital Papillary Adenocarcinoma:
Initial Consideration: A sweat gland-derived tumor like a hydrogenoma was considered due to hyaline and cystic areas.
Malignant Features: Polymorphism and mitosis indicated malignancy.
Location-Specific Differential: Given its location on the finger, Aggressive Digital Papillary Adenocarcinoma was highlighted as a crucial differential, even if cytologically bland, due to its potential for aggressive behavior and metastasis.
Key Takeaway: Any adnexal tumor on the digits warrants consideration of Aggressive Digital Papillary Adenocarcinoma, regardless of benign-appearing cytology.
6:08 Case 4: Malignant T-Cell Lymphoma (Pending Classification):
Description: The case presented with an inflammatory infiltrate, interface changes, and epidermal involvement.
Status: A definitive classification was still pending further results.
7:09 Case 5: Palisaded Encapsulated Neuroma (PEN):
Key Features: Appeared like a schwannoma in the skin, sharply circumscribed with a capsule, and growing from a nerve (EMA positive perineurium).
Most Helpful Feature: The presence of characteristic clefts or cracks between nerve bundles, particularly in the dermis.
Initial Impression: Low power suggested a proliferating pilar tumor due to smooth borders and a transition to dense keratin.
Consideration: Pilomatrical differentiation with "ghost cells" was also discussed, but the retention of nuclei distinguished it from a typical pilomatricoma.
Key Takeaway: Follicular tumors often exhibit overlapping and blended features, making precise classification challenging.