A 51-year old African American man presents to your office asking about dark spots on the upper extremities and left inner thigh. The patient is unaware of the duration of the spots. He is otherwise asymptomatic, denying pain, bleeding, crusting, or irritation. However, he admits to mild pruritus when a scab forms. The patient has no other cutaneous concerns and has no personal or family history of skin cancer. On physical examination, he has diffuse hyperpigmented to slightly violaceous plaques on the chest, arms, abdomen, buttocks, and lower extremities, with over 50% body surface area involved.
Which of the following is the best diagnosis for this patient?
- Cutaneous T-cell lymphoma
- Lichen planus
- Pigmented purpuric dermatoses
b. Cutaneous T-cell lymphoma
This patient was diagnosed with cutaneous T-cell lymphoma (CTCL), a rare cancer characterized by the infiltration of malignant monoclonal T-lymphocytes in the skin. There are approximately 20 billion T-cells located in the skin, double the circulating quantity (Clark, 2010). T-cells function to protect our skin, helping it succeed as the first line of defense against pathogens. The incidence of CTCL is increasing, currently impacting 6.4 per million persons in the United States (Wilcox, 2017). CTCL disproportionately affects males and African Americans. There is also a substantial increase in incidence with age, with the median age of diagnosis in the mid-50s and a fourfold increase in patients 70 years or older (Wilcox, 2017).
The two most common subgroups of CTCL presenting in two thirds of patients are mycosis fungoides (MF) and Sézary syndrome. MF is the most common form of CTCL, representing 44%–62% of cases, and has a very indolent course (Bagherani & Smoller, 2016). Patients present with progressive skin lesions that begin as macules and progress to patches, infiltrated plaques, and tumors. The patch and plaque stages of MF present clinically with large (>5 cm), pruritic, and multifocal lesions. The lesions classically appear in non-sun-exposed areas; however, they may also occur in areas exposed to the sun (Wilcox, 2017). The plaque stage is more elevated, whereas scaling and pigmentary changes are seen more in the patch stage. Our patient is an example of someone in the plaque stage. Diagnosing CTCL is challenging, and it is commonly mistaken for other benign skin conditions because of nonspecific clinical and pathologic characteristics. The differential diagnosis of CTCL includes atopic dermatitis, psoriasis, parapsoriasis, lichen planus, and pigmented purpuric dermatoses. Therefore, the median time from symptom onset to diagnosis is, on average, 3–4 years but can exceed four decades (Wilcox, 2017).
Multiple skin biopsies may be required to make a definitive diagnosis of CTCL because patients may exhibit different morphologic and phenotypic presentations. Skin biopsy and blood tests are frequently “suggestive” of a diagnosis or may not distinctly visualize cancer cells (Clark, 2010). Occasionally, it is necessary to acquire multiple biopsies as the histological findings may evolve into the classic diagnostic phenotype over time (Pulitzer, 2017). T-cell rearrangement studies are often done on the histologic specimens as well as T-cell markers to confirm the diagnosis. The presence of malignant T-cells and identifying clonality is required to make a precise diagnosis and differentiate CTCL from other common benign dermatologic diseases. Flow cytometry is utilized to assess peripheral blood specimens of patients for staging purposes in MF and diagnosis in Sézary syndrome (Pulitzer, 2017).
It is recommended that patients with CTCL be assessed by a multidisciplinary team composed of dermatologists, oncologists, dermatopathologists, and radiation oncologists. Accurate staging utilizing the lesion characteristics, lymph node involvement, metastasis, and blood classification system is important in the risk stratification of CTCL. Patients with only patches and plaques have Stage I disease. This is further subdivided into Stage IA if there is less than 10% body surface area involved or Stage IB if there is greater than 10% body surface area involved (Wilcox, 2017). Therapeutic treatment options include skin-directed therapies and systemic therapies (Jawed, Myskowski, Horwitz, Moskowitz, & Querfeld, 2014). Skin-directed therapies are reserved for treating Stages IA–IIA and involve less than 20% of the body surface area. Common treatment modalities include topical corticosteroids, topical nitrogen mustard, phototherapy, and radiation therapy. Systemic therapies include Vitamin A derivative medications, immunomodulators, and chemotherapy and are reserved for advanced and treatment-refractory CTCL (Jawed et al., 2014).
CTCL is a chronic disease that frequently relapses after cessation of therapy. In most cases, MF, the most common type of CTCL, has an indolent, chronic course lasting from years to decades. The prognosis of MF is good when in the patch to plaque stages; however, tumor-stage CTCL has a very poor prognosis. Overall, many patients with MF die because of unrelated causes (Wilcox, 2017).
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