Summary
Highlights
This session continues the discussion on malignant epithelial tumors, focusing on four specific slides: transitional cell carcinoma, follicular carcinoma, papillary carcinoma of the thyroid gland, and seminoma.
Transitional cells line the urinary tract. Normal transitional epithelium has 5-7 layers; more layers indicate papilloma or carcinoma. Key features of transitional cell carcinoma include increased cell layers, pleomorphism, and mitosis. It's graded as low or high based on nuclear pleomorphism, cellularity, mitosis, and necrosis. Invasion into smooth muscle is a sign of poor prognosis.
Follicular carcinoma represents 5-15% of primary thyroid carcinomas and is associated with iodine deficiency. It can be difficult to distinguish from follicular adenoma grossly. Histologically, differentiation relies on the presence of capsular and/or vascular invasion, identified by observing thyroid follicles within the capsule or blood vessels.
Papillary carcinoma is the most common type of thyroid cancer (85% of cases), often linked to ionizing radiation exposure in the neck. Histological features include papillary clusters with a fibromuscular core and characteristic 'Orphan Annie eye' nuclei (optically clear nuclei). While not always present, psammoma bodies are another diagnostic feature, indicating a favorable prognosis with over 95% ten-year survival.
Seminoma is a germ cell tumor found in the testes (disgerminoma in ovaries, germinoma in mediastinum), with similar histological features across locations. Its precursor is intratubular germ cell neoplasm (ITGCN). Seminomas express transcription factors like Oct3/4, Nanog, and placental alkaline phosphatase. Histologically, they show clusters of tumor cells separated by fibrous septae, with round to polygonal cells, centrally placed nuclei, clear cytoplasm, and presence of lymphocytes.