Benign mesenchymal tumours
How benign tumours of fat, fibrous tissue, muscle, cartilage, bone and vessels are named by the tissue they copy, why most grow slowly inside a capsule, how they still cause harm by site, and where intermediate tumours such as desmoids fit.
By the end, you can
- Name benign mesenchymal tumours by the tissue they resemble, and give their malignant counterparts.
- Describe the gross and microscopic appearance of a lipoma, a leiomyoma and a dermatofibroma.
- Explain why most benign mesenchymal tumours are encapsulated, and how they still cause harm by size and site.
- Explain why desmoid fibromatosis is intermediate, relating CTNNB1 and APC mutations to β-catenin.
- Explain what replaces grade and stage for benign and intermediate tumours, using the WHO behaviour categories.
What it is
A benign mesenchymal tumour is a clonal growth of cells that resemble a mature connective tissue (fat, fibrous tissue, smooth or skeletal muscle, cartilage, bone, vessels or nerve sheath) and that does not metastasise. It is named by adding -oma to the tissue it copies. Intermediate tumours, such as desmoid fibromatosis, infiltrate and recur but rarely or never metastasise.
3 types to tell apart
- Benign
- Expansile, usually circumscribed or encapsulated, rarely recurs after complete removal: lipoma, leiomyoma, dermatofibroma, haemangioma, schwannoma.
- Intermediate, locally aggressive
- Infiltrates and recurs but does not metastasise: desmoid fibromatosis, atypical lipomatous tumour.
- Intermediate, rarely metastasising
- Usually local, with metastasis in a small minority: dermatofibrosarcoma protuberans.
US spelling: tumours → tumors, tumour → tumor.
Normal function
Connective tissues and the cells that maintain them
Mesenchymal cells make and live in their own matrix: lay down the collagen of and , adipocytes fill with fat, and chondrocytes make . Bone, smooth and skeletal muscle, blood and lymphatic vessels and the sheaths of peripheral nerves belong to the same family.
In adults these cells divide slowly and only when needed: after injury, under hormones (the myometrium in pregnancy) or as fat stores grow. Growth signals, contact with neighbours and the matrix keep each tissue at its proper size.
Benign tumours of these tissues outnumber sarcomas by roughly a hundred to one, and lipoma is the commonest.
Underlying change · Step 1 of 5
A clone that copies its tissue, named by it
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
Lipoma and leiomyoma: what they look like
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 3 of 5
Dermatofibroma, and the desmoid as a locally aggressive tumour
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 4 of 5
Why most stay encapsulated, and how they still cause harm
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
Benign, intermediate or malignant: what replaces grade and stage
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 .