Pseudolymphomas of the skin (overview)L98.8

Stag and Luke 1965

Benign, histologically and clinically not always clearly distinguishable from malignant lymphomas of the skin, reactive, polyclonal, self-limited, lymphoreticular proliferations of the skin of different etiology and different clinical morphology.

According to aetiology and clinical presentation:

• Drug reaction:
  • Lymphocytic drug reaction
• Arthropod reaction and idiopathic:
  • Lymphadenosis cutis benigna (Borrelia lymphocytoma)
• Virus-induced pseudolymphoma (HSV infection- Leinweber B et al. 2006)
• Contact allergy:
  • Lymphomatoid contact allergy
• Unexplained:
  • Lymphocytic infiltration of the skin (entity?)
  • Erythema migrans arciforme et palpabile
  • Lymphomatoid papulosis
  • Actinic reticuloid
  • Angiolymphoid hyperplasia with eosinophilia
  • Cutaneous inflammatory pseudotumor (very rare)
  • Angioimmunoblastic cutaneous T-cell lymphoma (rare)
  • Other unclassifiable pseudolymphomas.

Pseudolymphomas can be classified according to immunophenotype as follows:

• Pseudolymphomas with a B-cell immunophenotype
  • Lymphadenosis cutis benigna
  • Cutaneous inflammatory pseudotumor
• Pseudolymphomas with a mixed B-cell/T-cell immunophenotype
  • Lymphocytic drug reaction
• Pseudolymphoma with a T-cell immunophenotype
  • Actinic reticuloid
  • Lymphomatoid contact allergy

Clinic, histology, PCR, Southern blot, immunohistochemistry.

The expression of monoclonal kappa- or lambda- light chains is in contrast to the polyclonal expression in reactive hyperplasia (pseudolymphoma) generally considered as malignant event. However, B- and T-cell pseudoclones are found in up to 20% of cases of pseudolymphomas.

In cutaneous B-cell lymphomas and cutaneous T-cell lymphomas the clonal rearrangement of the Ig chains can be detected either by immunohistochemical analysis with monoclonal antibodies or by immunogenotyping using Southern blot or PCR. The immunohistochemical technique has the advantage of the exact allocation of the antigen in the tissue, but is less sensitive (background staining). Southern blotting can make clonal cells visible in more than 5% of the cells of the lesion; the PCR technique is more sensitive with detection of < 0.1% of clonal cells.

Favourable (monitoring of the clinical course and ensuring lack of system participation).

The term "pseudolymphoma" covers a group of different clinical and histological entities that differ in their clinical and histological appearance and immunophenotype. It is desirable to name the known and historically founded terms in this way. In a larger French survey series among dermatologists and pathologists (122 dermatologists, 64 pathologists) it became obvious that the term "pseudolyphoma" has neither from clinical morphological view nor from histopathological view a uniform identification (Levy E et al. 2013).

1. Braun RP et al (2000) Cutaneous pseudolymphoma, lymphomatoid contact dermatitis type, as an unusual cause of symmetrical upper eyelid nodules. Br J Dermatol 143: 411-414
2. Böer A et al (2008) Pseudoclonality in cutaneous pseudolymphomas: a pitfall in interpretation of rearragnement studies. Br J Dermatol 159: 394-402
3. Cogrel O et al (2001) Sodium valproate-induced cutaneous pseudolymphoma followed by recurrence with carbamazepine. Br J Dermatol 144: 1235-1238
4. Gerlini G et al (2003) Specific immune therapy-related cutaneous B-cell pseudolymphoma with following dissemination. J Eur Acad Dermatol Venereol 17: 208-212
5. Stag P, Luke R (1965) Reactive pseudolymphoma, nodular type. Arch Derm 19: 408-409

6. Hussein MR (2013) Cutaneous pseudolymphomas: inflammatory reactive proliferations. Expert Rev Hematol 6:713-733.

7. Kulow BF et al (2002) Progression of cutaneous B-cell pseudolymphoma to cutaneous B-cell lymphoma. J Cutan Med Surg 6: 519-528

8. Leinweber B et al (2006) Histopathologic features of cutaneous herpes virus infections (herpes simplex
   ,herpes varicella/zoster): a broad spectrum of presentations with commonpseudolymphomatous
   aspects. On J Surg Pathol 30:50-58.

9. Levy E et al (2013) Pseudolymphoma of the skin: ambiguous terminology: a survey among dermatologists and pathologists. Ann Dermatol Venereol 140:105-111.

10. Marchesi A et al (2014) Tattoo ink-related cutaneous pseudolymphoma: a rare but significant complication. Case report and review of the literature. Aesthetic Plast Surgery 38:471-478
11. Moreno-Ramirez D et al (2003) Cutaneous pseudolymphoma in association with molluscum contagiosum in an elderly patient. J Cutan pathogen 30: 473-475
12. Pulitzer MP et al (2013)CD30+ lymphomatoid drug reactions. At J Dermatopathol 35:343-350
13. Ter-Nedden L (2018) test your expertise. Pseudolymphoma in herpes simplex infection. Act Dermatol 44: 89-91