Lymphoma & related disorders
Lymphomatoid papulosis (LyP)

Topic Completed: 1 August 2011

Minor changes: 26 March 2021

Copyright: 2001-2021,, Inc.

PubMed search: lymphomatoid papulosis [title] LyP

Dragos C. Luca, M.D.
Page views in 2020: 1,342
Page views in 2021 to date: 493
Cite this page: Lymphomatoid papulosis (LyP). website. Accessed April 18th, 2021.
Definition / general
  • LyP is a chronic, self healing skin disease composed of large, atypical, anaplastic, immunoblastic or Hodgkin-like cells in a marked inflammatory background (WHO 2008)
  • Rare (0.1 - 0.2 cases per 100,000)
  • Mostly adults (median age 45 years), but also children
  • M:F ratio 2 - 3:1
  • Skin lesion but no known extracutaneous disease within 6 months of initial diagnosis
  • Usually trunk, especially buttocks and extremities, rarely oral mucosa
  • Unknown, but endogenous retroviral elements have been identified
Clinical features
  • Self healing, recurrent, papular subcutaneous nodules less than 1 cm on extremities, trunk, face, genitals
  • Papular, papulonecrotic or nodular skin lesions at different stages of development; may disappear in 3 - 12 weeks
  • Clinically not considered malignant despite frequent monoclonality
Prognostic factors
  • Probably benign, but 20% associated with lymphoma (mycosis fungoides, cutaneous anaplastic large cell lymphoma, Hodgkin lymphoma, up to 40 years later) and microscopically resembles lymphoma
  • Generally excellent prognosis (only 2 of 118 patients 2 died of systemic disease, Blood 2000;95:3653)
Case reports
Postulated normal counterpart
  • Activated skin-homing T lymphocyte
Gross description
  • Grouped or disseminated papules / nodules
Gross images

Images hosted on other servers:

papules limited
to the right cheek


Microscopic (histologic) description
  • Large pleomorphic lymphoid cells with convoluted nuclei; some resemble Reed-Sternberg (RS) cells; also plasma cells and eosinophils
  • Extremely variable histology that correlates in part with the age of the lesion (types, A, B and C, with overlapping features)
    • Type A: small clusters of large, sometimes multinucleated or RS-like, CD30+ cells, admixed with numerous inflammatory cells (histiocytes, small lymphocytes, neutrophils, eosinophils)
    • Type B: uncommon (< 10%); epidermotropic infiltrate of of small atypical cells with cerebriform nuclei similar to Mycosis fungoides
    • Type C: monotonous population or large clusters of large CD30+ T cells with relatively few admixed inflammatory cells
  • Granulomatous eccrinotropic variant: Am J Clin Pathol 2003;119:731
Microscopic (histologic) images

Images hosted on other servers:

Multiple images and review

Positive stains
Negative stains
  • CD15, EMA, ALK, CD8 (usually)
  • CD30, CD8 (type B)
Molecular / cytogenetics description
  • Clonal rearrangement of T cell receptor genes in 60%; t(2,5) negative
Differential diagnosis
  • Arthropod bites, nonneoplastic disorders (usually have atypical CD30+ cells but polyclonal for T cell receptor rearrangements and polyclonal or oligoclonal for B cell immunoglobulin rearrangements, Am J Surg Pathol 2003;27:912)
  • Mycosis fungoides: lymphomatoid papulosis type B
Back to top
Image 01 Image 02