Carcinomas: malignant epithelial tumours
How carcinomas are typed by what their cells imitate (squamous cell, adenocarcinoma, urothelial, undifferentiated), how keratin pearls and glands are read, why they spread first by lymphatics, and how cytokeratins prove epithelial origin.
By the end, you can
- Name the main carcinoma types and relate each to the epithelium it imitates and its usual sites.
- Describe the gross appearance of a carcinoma and the microscopic hallmarks of squamous and glandular differentiation.
- Apply the in situ and invasive distinction to carcinomas of different organs.
- Explain why carcinomas spread first through lymphatics to regional nodes, and what stage records.
- Explain how cytokeratin immunohistochemistry identifies a carcinoma and helps find the primary site.
What it is
A carcinoma is a malignant tumour of epithelial cells: it invades through the basement membrane and can metastasise. Carcinomas are typed by the differentiation their cells show, mainly squamous cell carcinoma, adenocarcinoma and urothelial carcinoma, with undifferentiated carcinoma where no line is visible; cytokeratins mark them all as epithelial.
4 types to tell apart
- Squamous cell carcinoma
- Imitates squamous epithelium: nests with keratin pearls and intercellular bridges. Skin, mouth, larynx, oesophagus, cervix, anus, and bronchus after squamous metaplasia.
- Adenocarcinoma
- Imitates glands: tubules, papillae and mucin. Colon, stomach, pancreas, lung, breast, prostate, endometrium.
- Urothelial carcinoma
- Imitates urothelium (older name: transitional cell carcinoma), papillary or flat. Renal pelvis, ureter, bladder.
- Undifferentiated carcinoma
- No recognisable squamous or glandular features; identified as epithelial by cytokeratins.
US spelling: tumours → tumors, tumour → tumor.
Normal function
Epithelial cells, their cytokeratins and their lymphatic drainage
Epithelial cells line every surface and gland, and their structure shows what they do. Cells of are joined by many desmosomes and fill with keratin as they mature towards the surface; and glandular cells sit around a lumen and secrete mucin or other products; lines the urinary tract. All share a skeleton of cytokeratin intermediate filaments, whose exact types differ between epithelia.
Epithelium lies on a . The beneath holds blood capillaries and lymphatic capillaries, thin-walled channels with loose junctions that collect tissue fluid and drain it, in a fixed order, to regional lymph nodes. The cytokeratin skeleton and this lymphatic drainage explain how carcinomas are recognised and how they usually spread.
Underlying change · Step 1 of 5
Carcinoma types: named by what the cells imitate
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 5
Keratin pearls and glands: reading the differentiation
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 5
In situ and invasive: one rule in every organ
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 4 of 5
Spread: lymphatics first, then the blood
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 5 of 5
Proving epithelial origin: cytokeratins and the unknown primary
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 9 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .