Frozen section of skeletal muscle stained with nonspecific esterase. (Original magnification: 100x)
A 45-year old male firefighter with diabetes mellitus presents with chief complaint of lower back pain, right proximal thigh weakness, and minimally elevated CPK. Spine imaging shows multi-level degenerative joint disease and moderate spondylolisthesis. A skeletal muscle biopsy is obtained from the patient’s right thigh. What findings are seen in the esterase stained frozen section shown of the right rectus femoris?
Answer: The findings are those of mild active/ongoing denervation-type change. The muscle fibers of interest are variably atrophic and acutely angulated with a suggestion of a tendency toward small group atrophy. The frozen section shows the muscle fibers of interest with over-reactivity with the esterase preparation (increased staining intensity, dark), diagnostic of denervation-type change. Mildly elevated CPK levels may be seen in the setting of denervation-type change.
The case shows denervation-type changes; therefore, it is not normal. No ragged red fibers are present to suggest mitochondrial myopathy. No endomysial chronic inflammation is seen for diagnosis of polymyositis-type injury pattern. No dystrophic changes (increased endomysial fibrosis, fatty replacement, or muscle fiber injury) are seen to support a dystrophic process.
References:
Cai C, Anthony DC, Pytel P. A pattern-based approach to the interpretation of skeletal muscle biopsies. Mod Pathol. 2019 Apr;32(4):462-483. PMID: 30401945.
Dubowitz V, Sewry CA, Oldfors A. Neurogenic Disorders. In: Muscle Biopsy: A Practical Approach, 5th ed. Elsevier, London, United Kingdom; 2021: 201-213.
Quick note: This post is to be used for informational purposes only and does not constitute medical or health advice. Each person should consult their own doctor with respect to matters referenced. Arkana Laboratories assumes no liability for actions taken in reliance upon the information contained herein.
