Pseudolymphomas of the skin: causes, symptoms, diagnosis, treatment

Skin pseudolymphomas are a group of benign lymphoproliferative processes of a reactive nature of a local or disseminated type that can be resolved after removal of the damaging agent or non-aggressive therapy.

B-cell pseudolymphoma (syn: benafrosted BF, skin lymphocytoma, Spiegler-Fendt sarcoid), is more common in children and young men. Clinically it is quite clearly delineated, small, pinkish or bluish-red, solitary or (more rarely) multiple small-knuckle elements. Sometimes there are infiltrative-plaque foci with a flat or raised surface around which are located small elements, as well as solitary knotty foci. The most frequent localization is the face, ears, neck, nasal region of mammary glands, axillary hollows, scrotum. Sometimes there are symmetrical disseminated miliary nodules on the face and trunk. There may be changes in regional lymph nodes and peripheral blood, but the general condition of patients is good. The development of the disease is associated with spirochete Borrelia burgdorferi, penetrating the skin with bites of ticks - Ixodes ricinus.

Pathomorphology. Epidermis unchanged, only slightly thickened, under it there is a narrow strip of collagen separating it from the infiltrate. The latter is clearly delineated, located around the vessels and appendages, less often diffuse, occupying the entire dermis, extending to the subcutaneous tissue. The cellular composition of the infiltrate is rarely monomorphic, and N. Keri and N. Kresbach (1979) divide the lymphocyte into three types: lymphoreticular, granulomatous and follicular, although they do not deny the existence of mixed types. The basic cellular composition is small lymphocytes, centrocytes, lymphoblasts and individual plasmocytes. Among them are the histiocytes (macrophages), forming the so-called starry sky. Individual histiocytes can be multi-nuclear, and phagocytized material (polychromatic bodies) can be located in their cytoplasm. The macrophages are distinctly visible due to their high content of hydrolytic enzymes. Sometimes, in the marginal zone of the infiltrate, neutrophilic and eosinophilic granulocytes are found, as well as tissue basophils. In the follicular type, there are pronounced embryonic centers that mimic the secondary follicles of the lymph node, consisting of a broad lymphocytic shaft and a pale-colored center, in which there are mainly centrocytes, histiocytes, centroblasts, sometimes with admixture of plasmocytes and immunoblasts. The clinical manifestation of this disease histologically corresponds mostly to lymphoreticular and follicular types. The activity of stromal elements in the form of a fibroblastic reaction, neoplasm of vessels and an increase in the number of tissue basophils are very characteristic for lymphocytoma. With disseminated form this picture is more pronounced and the quality of the process is more difficult to recognize.

Phenotyping reveals positive markers of B-cells (CD19, CD20, CD79a) in the follicular component, concentric chains of dendritic CD21 + cells are also found in it. Interfollicular spaces contain CD43 + T-lymphocytes. Reaction with IgM and IgA - light chains confirms the polyclonal composition of the infiltrate. Genotyping does not reveal reorganization of Ig genes or intrachromosomal translocation. Differentiate the B-cell pseudolymph from immunocytoma, B-lymphoma from follicular center cells, and MALT-type lymphoma.

T-cell pseudolymphoma (syn: lymphocytic infiltration of Jessner-Kanof) occurs mainly in adult males, mainly on the forehead and sides of the face, as well as on the neck, occipital region, trunk and extremities, in the form of separate or multiple foci of cyanotic red or a brownish-red color. The disease begins with the appearance of papules, which, due to peripheral growth, form clearly delineated plaques with a smooth surface. In the central part, as a result of the regression of the process, plaques become ring-shaped. After a few weeks or months, they disappear without a trace, but can appear again on the same or other places. The association of this disease with chronic lupus erythematosus, which is not recognized by all, reaction to light, infection and medications indicate a reactive nature of the process.

Pathomorphology. The epidermis, mostly without any changes, in the subpapillary and reticular layers of the dermis, large, often clearly delineated infiltrates, consisting of histiocytes, plasmocytes and small lymphocytes, tend to be located around the appendages of the skin and vessels. Formation of follicles and embryonic centers is not noted. In the upper parts of the dermis, a change in the collagen substance in the form of basophilia, thinning of bundles of collagen fibers, proliferation of fibroblasts and other mesenchymal elements is found. In phenotyping, the predominant pool in the infiltrate is CD43 + T lymphocytes.

[1], [2], [3], [4], [5]