Case 4--Lesion 2

A different type of lesion--a circumscribed, spongy, greyish nodule, 2 cm in diameter--was present in the left lower lobe.

 

Histologically, at low power, there are infiltrates of lymphoid cells, which at higher magnification are mature lymphocytes and plasma cells. There has been focal destruction of the normal alveolar architecture, accounting for the honeycombed appearance of the gross lesion. The lymphoid cells invade vascular walls, but lymphoepithelial lesions and necrosis are absent.

Given the presence of the nodules with light chain deposits seen on the previous page, what might these cells represent, and how would you find out if your hypothesis is correct? Answer

Clinical summary Case 4 continued

Table of Contents

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answer: This lymphoid infiltrate might represent a clonal population that is producing the aberrant light chains that are deposited in the other nodules. Therefore, immunoperoxidase stains for light chains were done to determine whether the cells represent a monoclonal or polyclonal proliferation.

Immunoperoxidase stains for kappa (left) and lambda (right) light chains in this lesion show a marked predominance of staining of cells with the kappa marker over those with the lambda marker (>8:1). This light chain restriction indicates a monoclonal population of cells. The normal ratio of kappa to lambda cells is 2:1.

Kappa

Lambda

Clinical summary Case 4 continued

Table of Contents