PA6.7 | Benign vs Malignant Morphology — Practical — Summary & Reflection

REFLECT

Pause here and test your visual memory without looking back:

1. Sketch (mentally or on paper) the gross differences between a uterine leiomyoma and a leiomyosarcoma — what three features would make you suspect the latter before you even cut?

1. If you saw a slide with normal-looking glands on one side and solid sheets of hyperchromatic cells on the other, what single question about the boundary between them would determine whether this is 'high-grade transformation within a pre-existing adenoma' or two separate findings?

1. A DCIS and an invasive carcinoma can have identical cytology — both may show Grade 3 nuclear features. What is the ONLY criterion that separates them?

Discuss your answers with a classmate or write them in your portfolio logbook before proceeding.

KEY TAKEAWAYS

Core take-home framework — Benign vs Malignant Morphology

Gross: 4-point check
• Margins (circumscribed vs infiltrative) • Cut surface (homogeneous vs necrosis/haemorrhage) • Mobility (free vs fixed) • Surface (smooth vs fungating/ulcerated)

Micro: 6 features of anaplasia
• Pleomorphism • High N:C ratio • Hyperchromasia • Prominent/irregular nucleoli • Atypical mitoses (most specific) • Tumour giant cells

Structural criteria of invasion
• Loss of architecture • BM breach (CIS → invasive) • Lymphovascular invasion • Perineural invasion

Grading
• G1 Well / G2 Moderate / G3 Poor / G4 Undifferentiated — grade the least differentiated component

Reading sequence (never skip): Gross circumscription → Micro architecture → Cytologic atypia → Invasion → Diagnosis + Grade

One sentence to remember: A tumour that infiltrates, lacks a capsule, shows heterogeneous necrosis grossly, and displays anaplastic cytology with atypical mitoses and lymphovascular invasion microscopically is malignant until proven otherwise — and the burden of proof is on the pathologist to disprove it.