Pseudolymphoma is not a specific disease but rather an inflammatory response to known or unknown stimuli that results in a lymphomatous-appearing but benign accumulation of inflammatory cells. In cutaneous pseudolymphoma, resemblance to lymphoma is usually most apparent histologically, but some examples may also mimic lymphoma clinically. When known, the inciting agent should be included within the diagnosis of cutaneous pseudolymphoma. The term pseudolymphoma without modification should be reserved for idiopathic cases.
Localized, nodular pseudolymphomas are more common and typically mimic B-cell lymphoma (for further discussion, see Lymphocytoma Cutis). A variety of specific diseases are sometimes referred to as pseudolymphomas simply because they may resemble lymphoma. These disorders often show broad patches and plaques and often mimic cutaneous T-cell lymphoma. Examples include actinic reticuloid, lymphomatoid contact dermatitis, and lymphomatoid drug eruptions. Note the images below.
Pseudolymphomatous drug eruption due to captopril, marked by erythematous to purple papules, patches, and plaques.
This erythrodermic pseudolymphoma (T-cell pattern) typifies drug-induced pseudolymphoma, which is most often secondary to anticonvulsant therapy.
In persons with pseudolymphoma, lymphocytes and other inflammatory cells are recruited to the skin in response to known or unknown stimuli. Most cases are idiopathic. Cases of cutaneous pseudolymphoma with known etiology include reactions to tattoo dyes, jewelry (especially gold), insect bites, medications, folliculitis, trauma, infections, vaccinations, and contactants. A discrete subset of pseudolymphoma, borrelial lymphocytoma, primarily occurs in Europe in areas endemic for the tick Ixodes ricinus. Borrelial lymphocytoma is a response to infection by Borrelia burgdorferi subsp afzelius conferred by a tick bite. Another subset of pseudolymphoma is the result of an unusual systemic response to medications, typically anticonvulsants (see Drug-Induced Pseudolymphoma Syndrome).
No frequency data are available for cutaneous pseudolymphoma; the condition is uncommon but not rare.
Pseudolymphoma is not associated with mortality. Localized variants rarely result in morbidity other than minor pain or pruritus. Rare cases of cutaneous pseudolymphoma have been described in which the pseudolymphoma has evolved into cutaneous lymphoma.
Although 90% of reported patients with pseudolymphoma are white, racial predilection has not been established.
In reported cases of localized pseudolymphoma, the female-to-male ratio is approximately 2:1. No significant epidemiologic data are available regarding entities in the T-cell pattern pseudolymphoma spectrum.
Individuals of any age may be affected, but localized, nodular pseudolymphoma is most common in early life. The mean age of onset is 34 years. Two thirds of patients are younger than 40 years at the time of biopsy. Approximately 8% of cases involve patients younger than 18 years. Borrelial pseudolymphoma is more common in children than in adults.
Lymphocytoma cutis must be differentiated from lymphoma. Most examples simulate B-cell lymphoma and show a nodular inflammatory infiltrate in the dermis. The key histologic features that favor pseudolymphoma over lymphoma include the presence of a mixed infiltrate that includes histiocytes, eosinophils, and plasma cells, in addition to lymphocytes, as shown in the image below.
Biopsy specimens of pseudolymphoma vary substantially, but they most often exhibit a mixed inflammatory infiltrate with prominent lymphoid follicle fo....
The infiltrate in lymphocytoma cutis tends to be more top-heavy, while most lymphomas are centered in the deep dermis or the subcutis. Lymphocytoma cutis typically shows germinal centers and tingible body macrophages. Occasional large lymphoid cells may be present; however, they rarely dominate the histologic picture.
Immunohistochemical staining may also be useful and generally shows a mixed B- and T-cell population with a high MIB-1–positive proliferative fraction. Staining for kappa and lambda light chains shows a polyclonal pattern of staining. Fresh, unfixed tissue may be required for adequate assessment of kappa/lambda labeling.
Some cases show a T-cell histologic pattern with a bandlike infiltrate in the papillary dermis, predominantly of small lymphocytes, with variable epidermotropism. Although these features mimic cutaneous T-cell lymphoma/mycosis fungoides, the clinical presentation is often characteristic.
When the offending agent is known, its removal results in resolution of the cutaneous pseudolymphoma. Cases of cutaneous pseudolymphoma documented to occur as a result of infection should be appropriately treated. In idiopathic cases of cutaneous pseudolymphoma, treatment is not mandatory. Cures may be affected via surgical removal, cryosurgery, or local irradiation. Some reports have noted a response to topical or injected corticosteroids and topical immunomodulators such as tacrolimus.
Patients with presumed pseudolymphoma in which the possibility of lymphoma cannot be excluded should be evaluated for the possibility of concurrent extracutaneous disease and followed for possible emergence of lymphoma.
In cutaneous pseudolymphoma, simple excision of the involved site can be curative in some cases.
The goals of pharmacotherapy for cutaneous pseudolymphoma are to reduce morbidity and to prevent complications.
These agents have anti-inflammatory properties and cause profound and varied metabolic effects. In addition, these agents modify the body's immune response to diverse stimuli.
Clinical Context: Adrenocorticosteroid derivative suitable for application to skin or external mucous membranes. Has mineralocorticoid and glucocorticoid effects resulting in anti-inflammatory activity. Treats inflammatory dermatosis responsive to steroids. Decreases inflammation by suppressing the migration of polymorphonuclear leukocytes and reversing capillary permeability.
Clinical Context: For inflammatory dermatosis responsive to steroids. Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reversing capillary permeability.
Clinical Context: Class I superpotent topical steroid; suppresses mitosis and increases synthesis of proteins that decrease inflammation and cause vasoconstriction.
Clinical Context: High-potency topical corticosteroid that inhibits cell proliferation; is immunosuppressive and anti-inflammatory.