Clinical summary continued: In 1997, when the new lesion was first noted radiographically, serum protein electrophoresis showed no abnormalities. Further, in 1998, a urinary protein electrophoresis was normal. A fine needle aspiration biopsy of the new nodule was performed in 10/99. No further treatment is contemplated at this time.

Histologic Changes

The biopsy tissue shown here was so firm that it had to be pushed out of the needle by a stylet. It is composed of a sparsely cellular, homogeneous, pink, extracellular material similar to that in the previous nodule. There was no evidence of malignancy.

 

At higher magnification, homogeneous, pink material with cracks, which typically occur, replaces parenchyma. The tentative diagnosis is amyloidoma.

What special stain is needed to confirm the diagnosis? Answer

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What special stain is needed to confirm the diagnosis?

Answer: A positive Congo red stain (shown here) viewed with polarized light (see below). A positive Congo red stain alone is not specific for amyloid.

When viewed with polarized light, two colors specific for amyloid are seen--light green and yellow. As one of the polarizing films is rotated, the green becomes yellow and the yellow, green. White birefringence (not shown here) is characteristic of collagen.

Final diagnosis: This reaction confirms the diagnosis of nodular amyloidosis (amyloidoma), which is recurrent in this case.

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