Summary
Highlights
The video introduces the second leg of the general pathology discussion, focusing on mixed and malignant epithelial tumors. It lists the slides to be covered: fibroadenoma (219), Wilms' tumor (196), cystic teratoma (88), cervix carcinoma in situ (14), invasive squamous cell carcinoma (70 and 152), basal cell carcinoma (187), and malignant melanoma (188).
Fibroadenoma is a benign breast tumor exclusively found in females, commonly in the 20-30 age bracket. It is firm and histologically characterized by dilated or compressed ducts surrounded by abundant stroma, which can be fibro-prophylaxis or fibro-myxoid. This falls under proliferative change without atypia.
Wilms' tumor is the most common malignant kidney tumor in children and infants, rarely seen in adults. It is associated with a WT1 gene mutation. Histologically, it's triphasic, composed of stromal, epithelial, and blastemal components, featuring small round cells forming tubules or gland-like structures.
A mature cystic teratoma is a benign tumor derived from three germ cell layers, often presenting as a cyst with sebaceous material. Microscopic features include stratified squamous epithelium, sebaceous glands, mucosynovi, cartilage, and fat. In 1% of cases, it can undergo malignant transformation, commonly found in the ovary but possible anywhere in the body.
Cervix carcinoma in situ (CIN) involves malignant cells occupying the entire thickness of the epithelium without invasion. The lining epithelium of the exocervix is stratified squamous. CIN is classified based on the involvement of atypical cells: CIN1 (lower one-third), CIN2 (over two-thirds), and CIN3 (full thickness or carcinoma in situ). Metaplastic events involving glands with atypical squamous cells can also be seen.
Invasive squamous cell carcinoma develops from carcinoma in situ and is characterized by nests or clusters of atypical squamous cells invading the stroma. Identification is based on keratinization, pink cytoplasm (eosinophilic), desmosomes (ladder-like appearance), and keratin pearls (concentric lamellation of keratin with entrapped glands), which indicate a well-differentiated tumor. Cytokeratin is a useful tumor marker.
Basal cell carcinoma is a malignant skin tumor, derived from basal cells, often connected to the lining epithelium. It forms nests of basal-oid cells, resembling a map. It's associated with the PTCH gene mutation, especially in Gorlin's syndrome. Key features include peripheral palisading (radially oriented peripheral cells) and a retraction space separating the nest from the stroma. Commonly found in sun-exposed areas like the nose.
Malignant melanoma is skin-derived, with 85-90% of cases being sporadic due to UV light exposure, more common in fair-skinned individuals, and sometimes associated with BRAF or RAS mutations. Grossly, it's typically larger than 1cm with irregular borders, varied color (purple to black to brown), and growing size. Histologically, it's composed of large melanin-producing cells (melanocytes) with melanin pigments. Immunostains like HMB-45 and S100 can aid diagnosis.