Amyloidoma secondary to insulin injection: Cytologic diagnosis and pitfalls

Abstract

Amyloidomas are rare tumors composed of deposits of amyloid protein not associated with systemic amyloidosis. They can present as an initial manifestation of a systemic disease process or can be a completely localized phenomenon. We present a case of amyloidoma associated with insulin injection site found incidentally in an 80-year-old male with multiple co-morbidities who presented with diverticulitis associated bleeding. A subcutaneous abdominal mass was found on physical examination. Imaging revealed a 5 cm × 1.6 cm homogenous subcutaneous lesion. A fine-needle aspiration (FNA) and core biopsy were performed under ultrasound guidance to reveal amorphous material proven to be amyloidosis at insulin injection sites (AIns) type amyloid. The patient had no treatment for this lesion and has had his care triaged to his more serious health problems. This is the first case of AIns type amyloidoma associated with insulin injection site reported in cytology literature. We highlight the cytologic findings and diagnostic pitfalls. As the incidence of diabetes is increasing, cytopathologists may encounter this lesion more often on FNA.

Keywords: Amyloid; amyloidoma; amyloidosis at insulin injection sites; diabetes; fine-needle aspiration; insulin injection site.

Figure 1

Computed tomography image of abdominal wall lesion. Sections were taken at 5 mm intervals. Image 31 of series #2 shows greatest dimensions of lesion as well as its homogenous nature

Figure 2

Fine-needle aspiration smears of amyloid, Diff Quik stain. (a) Smear shows abundant deep blue/purple colored amorphous material (×20). (b) On high power, this material resembles has tissue paper appearance, resembling keratin debris (×40)

Figure 3

Fine-needle aspiration smears of amyloid, Papanicolaou stain. (a) Orangophilic waxy material is abundant on this smear. Smaller globules in the lower left corner mimic anucleated squamous cells (×20). (b) High power demonstrates dense waxy appearance of amyloid; a few spindled cells are seen intermixed with amyloid (×40)

Figure 4

Core biopsy. (a) This core biopsy slide shows amorphous eosinophilic dense material (H and E, ×20). (b) The material is homogeneous and red with Congo stain (Congo, ×20). (c) The core biopsy shows apple green/yellow birefringence (Congo, under polarized light, ×40)