Cancer-Induced Lumbar Plexopathy — SCE Palliative Medicine MCQ

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ModeratePain ManagementCancer-Induced Lumbar PlexopathySCE Palliative Medicine

A 62‑year‑old woman with metastatic melanoma develops severe burning pain in the right thigh. Examination shows allodynia, hyperalgesia and reduced pin‑prick sensation in the L2–L3 dermatome. MRI confirms a tumour infiltrating the right lumbar plexus. What best describes this presentation?

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Correct answer: C — Cancer‑induced neuropathic pain due to direct tumour infiltration of the lumbar plexus (cancer‑related neuropathic pain under ICD‑11)

This presentation is characteristic of cancer‑related neuropathic pain due to direct tumour infiltration of the lumbar plexus: there are objective neuropathic signs (allodynia, hyperalgesia, sensory loss) in an L2–L3 distribution, plus imaging confirmation of plexus involvement. ICD‑11 specifically classifies such pain as chronic cancer‑related pain, distinguishing it from other neuropathic mechanisms ([pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/30586069/?utm_source=openai)). Hip osteoarthritis would produce nociceptive pain without dermatomal neuropathic signs; meralgia paraesthetica affects only lateral femoral cutaneous nerve (L2/L3 region but more confined distribution, without tumoral cause); inflammatory myopathy would produce weakness, not sensory neuropathic signs; diabetic neuropathy typically is distal, symmetric and metabolic rather than focal oncology‑related.

Reference: The IASP Taskforce classification, ‘The IASP classification of chronic pain for ICD‑11: chronic cancer‑related pain’ (Bennett et al. 2019) and NICE CG173 (2020) introduction noting neuropathic cancer pain due to direct neural invasion. https://pubmed.ncbi.nlm.nih.gov/30586069/