Cutaneous Lymphoid Hyperplasia (CLH) is a benign, non-cancerous skin condition. It is often classified as a “pseudolymphoma” because it clinically and microscopically mimics true cutaneous lymphoma, which is a cancer of the lymphatic system. Understanding the biological distinction between this reactive process and a genuine malignancy is key to addressing patient concern. This article clarifies what CLH is, how it is definitively told apart from cancer, and what the management approach involves.
What Cutaneous Lymphoid Hyperplasia Is
Cutaneous Lymphoid Hyperplasia is an exaggerated response of the skin’s immune system to an external stimulus. This reaction involves the temporary accumulation of various lymphocytes, which are the white blood cells that form the core of the immune defense. The process is reactive, meaning it is a direct consequence of the body attempting to defend itself against a perceived threat.
The condition typically manifests as one or a few localized skin lesions, often appearing as soft, reddish-brown to purplish nodules or firm plaques. These growths most commonly develop on the head, neck, and upper trunk. While many cases have no identifiable cause, CLH is frequently traced back to specific triggers that provoke the immune response.
Common inciting factors include the bite of arthropods like ticks or insects, foreign body reactions to tattoo ink or ear piercings, and certain medications, particularly some anticonvulsants. Infections with the bacterium Borrelia burgdorferi, the agent responsible for Lyme disease, are a well-documented cause, especially in European cases. Identifying and removing the trigger, when possible, is often the first step in managing the condition.
How CLH Differs From Malignant Lymphoma
The difference between CLH and malignant lymphoma lies in the fundamental nature of the cell growth. CLH represents a polyclonal expansion, meaning the amassed lymphocytes are a mixed population arising from many different parent cells. This diverse cell mixture is characteristic of a normal, reactive inflammatory process.
In contrast, cutaneous lymphoma is a monoclonal process. The proliferation is uncontrolled and originates from a single, abnormal parent cell that has lost its regulatory mechanisms. This single clone multiplies without purpose, forming a true tumor.
Histologically, a CLH lesion often shows evidence of organized structures, such as reactive germinal centers, which are the normal sites where lymphocytes mature during an infection. These centers typically contain tingible body macrophages, cells that actively clear debris from dying lymphocytes, reflecting an organized immune turnover. These organizational features and the presence of mixed cell types are generally absent in true lymphomas, where cell proliferation is disorganized. Furthermore, CLH lesions often have a rapid onset and may resolve spontaneously, while lymphomas are characterized by slow, persistent growth.
Confirmatory Diagnostic Testing
Distinguishing CLH from lymphoma requires a comprehensive evaluation beginning with a skin biopsy of the lesion. The tissue sample is examined under a microscope, which initially reveals the dense accumulation of lymphocytes in the dermis. Specialized laboratory techniques are then used to definitively characterize the nature of the cell population.
Immunohistochemistry (IHC) involves staining the tissue with specific antibodies to identify the various immune cell markers present. In CLH, IHC typically shows a mixed population of CD20-positive B-lymphocytes and CD3-positive T-lymphocytes, confirming the presence of both major immune cell types. The cells do not show the aberrant protein expression often seen in cancerous cells, mirroring a normal immune reaction.
The most precise method for confirming the benign nature is through molecular studies, such as T-cell receptor or Immunoglobulin gene rearrangement analysis. This testing determines the genetic diversity of the lymphocytes in the lesion. A finding of multiple, varied gene rearrangement patterns, termed a polyclonal result, confirms the diagnosis of CLH. Conversely, a monoclonal result, showing a uniform genetic signature, strongly suggests the presence of a single, cancerous clone, which points toward a lymphoma diagnosis.
Treatment and Prognosis
Management of Cutaneous Lymphoid Hyperplasia is typically conservative, given its benign nature and potential for spontaneous resolution. The initial approach involves identifying and eliminating any known triggers, such as discontinuing an implicated medication or treating a Borrelia infection with appropriate antibiotics. For many patients, no further action is necessary beyond careful observation.
If the lesion is persistent, cosmetically bothersome, or causing symptoms, localized treatments are often effective. These include injecting corticosteroids directly into the lesion (intralesional corticosteroids) to reduce inflammation and shrink the nodule. Potent topical corticosteroids applied to the skin surface can also be used in some cases.
Surgical excision may be performed if the lesion is small and localized, or if the diagnosis remains uncertain despite advanced testing. The long-term outlook for CLH is excellent, as the condition does not represent a cancer and rarely transforms into a true lymphoma. While lesions can occasionally recur or new ones may develop, CLH generally resolves with minimal intervention and does not pose a threat to overall health.