3.3.14 Pseudolymphomas (not Borrelia induced)

EH6Y

Lymphocytic infiltration, reactive lymphoid hyperplasia.

Epidemiological data for Borrelia lymphocytoma are known for about 2% (see chapter 2.2.9) for other subtypes is lacking.

Reactive pseudolymphomatous infiltrate of B-, T-, and combined T/B-cell type that mimic clinically and/or histopathologically malignant lymphomas.

In pseudolymphoma B - and T-lymphocytes and other inflammatory cells accumulate in the dermis and subcutis as a reaction to stimuli of different origin. Often a causative agent is missing. Cutaneous pseudolymphoma with known etiology include reactions to tattoo dyes, arthropods, medications, allergens, viral or bacterial infections (molluscum contagiosum, herpes, HIV, syphilis…) or vaccinations. A subset of pseudolymphoma is the result of an unusual systemic mixed T- and B- cell response to several drug classes.

UV light can produce a T-cell dominated actinic reticuloid and persistent contact allergens (nickel or para-phenylenediamine).

A specific subset of B- cell type pseudolymphoma, Borrelia lymphocytoma (see 2.2.9), primarily occurs in Europe in areas endemic for the tick Ixodes ricinus. Borrelial lymphocytoma is a tick bite response to infection by Borrelia burgdorferi subsp afzelius and garinii. Causative agents: Borrelia garinii and Borrelia afzelii (both in Europe), not Borrelia burgdorferi sensu strictu.

Different forms: localized erythematous macules sometimes confluent, solitary or multiple nodules, plaques. Occasionally disseminated; rarely with lymphadenopathy.

In Borrelia lymphocytoma lesions are often indolent soft blue-red nodules up to 5 cm. Post scabies lymphocytomas are localized or often disseminated. T-cell pseudolymphomas occur with localized plaques, nodules and disseminated papules or annular pattern. An erythroderma may also be seen. Some lesions may be also severely itchy. Red-blue lupoid infiltrate (diascopy).

Borrelia IgG and IgM titers raised in Borrelia lymphocytoma. In actinic reticuloid UV light provocation test. In lymphocytic infiltration immunoserology to exclude lupus erythematosus and blood count for leukemic infiltrate. Repeated biopsies with B or T-cell genetic rearrangement studies can help (but many benign conditions present monoclonal populations of lymphocytes, careful clinical-pathologic and molecular correlation is required).

No specific other tests.

Each primary cutaneous lymphoma can have a mimicker. Clinical appearance will be similar to the mimicked lymphoma.

• Malignant B- / T- cell lymphomas

• Disseminated cutaneous sarcoidosis

• Stage II syphilis