Cutaneous plasmacytosis pathology

Introduction

Cutaneous plasmacytosis presents with multiple reddish-brown nodules. It has most often been reported to affect the trunk but is also known to affect the face and extremities in adults and is predominantly seen in Asians. The aetiology is poorly understood.  

Histology of cutaneous plasmacytosis

In cutaneous plasmacytosis, histopathological examination shows perivascular and perineural plasma cell infiltrates in the dermis (figures 1–4) without evidence of folliculitis or other common causes of plasma cell infiltrates (figures 1–4)

Figure 1

Figure 2

Figure 3

Figure 4

Special studies for cutaneous plasmacytosis

It is important to demonstrate that the plasma cells are polyclonal. This can be done with kappa and lambda immunohistochemistry or in situ hybridisation. 

Differential diagnosis for cutaneous plasmacytosis

Other diagnoses to be considered include:

• Infection — Some infections cause dense plasma cell infiltrates (eg, syphilis, Lyme disease). Special stains, culture or more sophisticated investigations are required to rule out an atypical infection
• Lymphoma/plasmacytoma — Clonality studies (kappa/lambda stains or gene rearrangement studies) may be needed to exclude a plasma cell-rich lymphoma.