Lymphomatoid papulosis (LyP) was originally considered a pseudolymphoma until it was classified by the World Health Organization—European Organization for Research and Treatment of Cancer (WHO-EORTC) as an indolent cutaneous T-cell lymphoma in 2003-4. LyP and primary cutaneous anaplastic large cell lymphoma belong to the CD30+ cutaneous lymphoproliferative disease.

LyP is very rare with a prevalence of 1-2 cases per million population in US.

Lyp appears in patients in 50’s as a recurrent chronic papulonecrotic or papulonodular skin disease mostly on the trunk and limbs with histologic features suggestive of a malignant lymphoma.

The lesions heal spontaneously over 1-2 months. LyP may be associated with or may develop large cell anaplastic lymphoma in about 10% of cases.

   •     Microscopic:

  • Upon low-power histologic examination, lymphomatoid papulosis shows a wedge-shaped dense dermal infiltrate of lymphoid cells with numerous eosinophils, neutrophils, and up to 50 % atypical lymphocytes, raising possibility of lymphoma.
  • What is next?
  • Time to identify the type of lymphocytes in the infiltration….T-cell, B-cell or mixed population?
  • A. We need an initial panel of  immunohistochemistry: I usually get 7 CD’s:
  • For all leukocyte: CD45 (Leukocyte Common Antigen, LCA)
  • For T-cells: CD3, CD5, CD30
  • For B-cells: CD20, 79a
  • For Plasma cell: CD138
  • B. If the infiltrating cells are a mixture of T and B-cells with or without plasma cells and there is no dominant cell type, my tentative impression will a benign inflammatory infiltrate.
  • C. If most cells are T-cells with some degree of cytologic atypia and epidermotropism, I will order additional T-cell panel (CD4, CD7,CD8). A reactive process will have mixed CD4 and CD8 T-cells. MF typically loses CD7 expression.
  • D. If most cells are T-cells and CD30+, then I am dealing with CD30+ lymphoproliferative disorder ((lymphomatoid papulosis or  cutaneous primary anaplastic large cell lymphoma).
  • Histologically, lymphomatoid papulosis is divided into several subtypes, of which 75% of cases will be Type A.
  • Type A is characterized by large (25-40 µm) CD30+ atypical lymphocytes mixed with eosinophils and neutrophils. The large tumor cells have polymorphic convoluted nuclei with prominent nucleolus and binucleate Reed- Sternberg cells-like cells.

•       Immunoprophile

  • CD3+, CD4+, CD5 +/-, CD8-, CD20-, CD30+, CD56-

•       Differential diagnosis:

  • Mycosis fungoides: Dermal band-like (not wedge-shaped infiltrate). Epidermotropism may be prominent. As a rule neutrophilic and eosinophilic infiltration is not seen.
  • Anaplastic large cell lymphoma: Clinical, microscopic and immunohistochemical features of lymphomatoid papulosis and anaplastic large cell lymphoma (ALCL) may overlap.
  • Hodgkin’s disease
  • Insect bites: Wedge-shaped infiltrate composed of lymphocytes and eosinophils. Slightly abnormal lymphocytes may be present .

•         Final comment:

  • Clinicopathologic correlation is a must  to establish an accurate diagnosis.

Deba P Sarma, MD, Omaha

DOWNLOAD: Lymphomatoid papulosis