Normal serum protein electrophoresis and urine protein electrophoresis studies exclude multiple myeloma. NLCA does not cause any abnormal findings in these studies. A urinalysis or 24-hour urine can be checked for protein. Proteinuria is not a feature of localized cutaneous disease but can be seen in systemic amyloidosis. In some patients, imaging studies have included chest x-ray, ECG, and abdominal ultrasound.
Skin biopsy provides the definitive diagnosis.
No special tissue preparation or handling is required before delivering the specimen to the laboratory. Special stains and immunohistochemistry are helpful. Sites for an optimal biopsy include the epidermis, papillary dermis, and reticular dermis. The amyloid in NLCA is located in the reticular dermis and clearly differentiates NLCA from other forms of amyloidosis. A shave biopsy or other superficial sample may not include enough reticular dermis to complete the diagnosis.