Most of the commonly diagnosed CLH are thought to be due to idiopathic etiology; however, some may be associated with bites or stings from arthropods, infections such as herpes zoster and Borrelia burgdorferi, recent tattoos, vaccinations, and use of gold jewelry2. Medications that can be associated with CLH include phenytoin (hydatoin-associated pseudolymphoma syndrome), carbamazepine, phenobarbitols, cyclosporine, calcium channel blockers, and H₁ and H₂ antagonists. Due to this variety of causative agents, the identification of the etiologic factors of this lesion can be considered a very enigmatic dilemma; our case was deemed to be idiopathic. It has been proposed that rather than being the target of the immune response; these agents alter the lymphocyte reactivity in a way to promote a typical CLH response.

Clinical history taking should include the symptomology and duration of the lesion as well as the nature and pace of progression. CLHs are usually slow growing lesions, mostly painless, and have a slow pace of progression with an indefinite rate of growth. The history should also include the so called lymphoma B symptoms such as fever of unknown origin, unexplained weight loss, night sweats, fatigue, and malaise. Our patient did not have any of these symptoms, further lessening the probability of this diagnosis. A general examination should be part of the routine analysis for cutaneous lesions in order to rule out the distribution of skin lesions and peripheral lymph nodes. Extracutaneous involvement should be ruled out by complete blood count, general chemistry panel, and chest radiographs. These lesions are usually solitary but may occur as papules, plaques, or nodules. They usually have a firm to doughy consistency and range from red-brown to violet in color. Use of topical and systemic corticosteroids should be discontinued for at least 4 weeks before biopsy as these agents attenuate the lymphoid infiltrates. The most diagnostic area of biopsy in these lesions is the deepest portion. In our case, i.e., a solitary lesion, it was best to perform an excisional biopsy as the inflammatory changes associated with an incisional biopsy would change the local environment. If uncertainty remains regarding the diagnosis between a pseudo and true lymphoma, further tests may be ordered, such as computed tomography of the chest and abdomen and bone marrow biopsies.

The differential diagnoses for an acquired, long standing, painless, firm to doughy lesion occurring on the forehead are numerous, ranging from the benign solitary neurofibroma to malignant lymphomas. The key diagnoses to include are neurofibroma, lipoma, drug eruptions, infectious and inflammatory granulomas, and metastatic carcinoma. It is important to always rule out cutaneous B-cell lymphoma (CBCL) and leukemia cutis, as they are aggressive lesions, and treatment can be completely tangential.

These lesions can resolve spontaneously, if the etiologic agents are removed, or might persist indefinitely, giving rise to a poor aesthetic outcome. Nodular scabies is a well-known clinical form of persistent CLH that presents as pruritic, persistent nodules for months even after specific treatment. Single standing lesions usually resolve after excisional biopsy. One of the most challenging outcomes is the close relationship with CBCL. Most patients subsequently diagnosed with CBCL receive a previous diagnosis of CLH based on biopsy results. Patients with papulosis, granulomatosis, and lymphadenopathy have a high chance of developing lymphomas 2. Some authors present this as a “concept of continuum”, where the cutaneous pseudolymphomas, such as CLH, represent the benign end of the lymphoproliferative continuum, with the intermediate form being clonal CLH, and the malignant extreme being true lymphomas. This concept is important when considering treatment options based on stage in the continuum, and regular follow up is needed due to the increased risk of clonally related lymphoma and the other lymphoid abnormalities usually associated with this lesion3.

CLH can be treated in a variety of ways based on the etiology. Lymphocytoma cutis, traditionally caused by B. burgdorferi, responds to cyclosporin therapy, as do some of the idiopathic varieties. Glucocorticosteriods (topical, intra lesional 5-40 mg/mL 1 mL monthly or systemic 60/40/20 mg 5 days each tapered), hydroxychloroquine 200 mg twice daily, and minocycline 50-100 mg twice daily have been used in the past with varied success4. Some studies also support the use of HIV antiviral triple therapy5 or topical tacrolimus6. Radiotherapy has been shown to be effective but is mostly considered a last resort. Recently, the use of pulsed dye lasers and photodynamic therapy has been shown to be effective in esthetic areas7. Our case was an atypical CLH; in most instances, these lesions cannot be distinguished from true lymphoma, and was hence treated as a localized lymphoma, i.e., excision, after the staging ruled out extra cutaneous disease. Due to the local and distant recurrences after any of the above treatments, this may have been followed by radiotherapy; this was not so in our case due to the patient's desires.

Key to the prevention strategy of CLH is to avoid the ingestion of, or contact with, any of the causative agents in patients with a suggestive clinical history, such as anticonvulsants, arthropods, gold jewelry, and hair dyes8.

Due to the overlapping clinical and histological characteristics of CLH with many other lesions, it is important to include and exclude this lesion in the differential diagnoses put forward for suspected cutaneous lesions.