PMC10115977_01
Clinical and paraclinical features of the patient. (A) Presence of two subcutaneous nodules on the left arm (arrows), (B) Soft tissue ultrasound of the left arm evidencing and measuring one subcutaneous mass, (C) MRI frontal slices of the left upper limb (T1 with gadolinium injection on the left, and T2 on the right), and (D) 18-FDG-PET-CT scan showing a 18-FDG uptake by the nodule (arrow) on the left arm.
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The initial clinical examination revealed two non-inflammatory mobile, firm but painless, subcutaneous nodules measuring 2 and 5 cm on the outer and inner sides of the left forearm (Figure 1A). A soft tissue ultrasound (Figure 1B) confirmed the two sub-cutaneous lesions of the left forearm, the main one measuring 4 cm in its longitudinal axe, associated with four enlarged lymph nodes located around elbow and armpit. An MRI of the left upper limb revealed the two sub-cutaneous lesions characterized by T2 hyposignal and enhancement upon gadolinium (Figure 1C). A 18-FDG-PET-CT-scan showed an isolated hypermetabolism (Figure 1D) colocalizing with the two subcutaneous masses and the enlarged local lymph nodes.
Histological analyses of the biopsy of one subcutaneous nodule. (A) HES section at low magnification (x10) evidencing granulomas with giant cells (arrows) phagocytizing the amorphous substance (*), (B) HES section at higher magnification (x40), (C) Section at low magnification (x4) stained with Congo Red evidencing the amyloid deposit (*), and (D) Detailed results of the mass spectrometry evidencing the insulin protein highlighted in yellow, along with the serum amyloid P-component in red (of note, immunoglobulin heavy gamma chains were of polyclonal origin).
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The surgical biopsy of one lesion revealed granulomatous remodeling in contact with amyloid deposits (Figures 2A,B), displaying red-green birefringence under polarized light after Congo red staining (Figure 2C). Proteomic analyses using mass spectrometry confirmed the insulin origin of the amyloid deposits leading to the diagnosis of insulin amyloidosis (Figure 2D).