Mycosis Fungoides
DEFINITION
MF is the most frequent variant of CTCL, usually arising in mid to late adulthood (median age at diagnosis, 55 to 60 years) with a male predominance of 2:1.
CLINICAL MANIFESTATIONS
Skin Signs.
Clinically MF is categorized as being in the patch, plaque, or tumor stage, but patients may simultaneously have more than one type of lesion. In early patchstage MF , there are single or multiple erythematous, scaly macules and patches that vary in size and are usually well defined. The color of the lesions may vary from orange to a dusky violet-red. The distribution classically favors non-sun-exposed sites, with the “bathing trunk” and intertriginous areas predominant early in the course of the disease. The eruption may be intensely pruritic or asymptomatic and occasionally may be transitory, disappearing spontaneously without scarring. Diagnosis at this stage may be difficult. Often a patient will recall a preceding “chronic dermatitis” for 10 to 20 years that may have been considered to be therapeutically resistant contact dermatitis, atopic dermatitis, psoriasis, or eczema. In any patient with a dermatosis that is refractory to the usual modalities of treatment, multiple biopsy specimens should be taken to pursue a diagnosis.
Patches may last for months or years before progressing to the plaque stage , or plaques may arise de novo. Plaques appear as sharply demarcated, scaly, elevated lesions that are dusky red to violaceous and variably indurated . Lesions in this stage may regress spontaneously or may coalesce to form large plaques with annular, arcuate, or serpiginous borders, and may clear centrally with disease activity remaining at the periphery of the lesion. There may be purpuric hyperpigmentation or hypopigmentation and poikiloderma .
The tumor stage may occur anywhere, but tumors have a predilection
for the face and body folds: axillae, groin, antecubital fossae, and, in women, the inframammary area. These may occur in pre-existing plaques or patches of CTCL, which suggests the development of a vertical growth phase . At this point, the neoplastic cells behave in a more biologically malignant manner, with vertical spread that leads to the clinical appearance of an expanding dermal nodule . De novo occurrence suggests metastatic spread by cells of a malignant T-cell clone. The nodules are reddish brown or purplish red and smooth surfaced, but they often ulcerate and may become secondarily infected . Growth rate is variable. Patients with tumors tend to have a more aggressive form of the disease than patients with patch and plaque disease.
Erythroderma may start de novo or follow MF. The nomenclature for erythrodermic phases of CTCL varies. It has been proposed that erythroderma be defined as the involvement of 80 percent of body surface area with lesions of ill-defined borders and that patients with a history of pre-existing MF be defined as having a separate syndrome of “erythrodermic MF.”
The skin is diffusely bright red with readily apparent scaling, but there may be characteristic symmetric islands of uninvolved skin . There may be sparing of the areas of skin that are frequently folded, such as the abdomen and antecubital and axillary areas. This sparing produces a finding often called the deck chair or folded luggage sign,. Some patients with the erythrodermic form of CTCL develop tumors.
Other Symptoms.
Patients may complain of fever, chills, weight loss, malaise, insomnia
secondary to the overwhelming pruritus, and poor body temperature homeostasis. There may be hyperkeratosis, scaling and fissuring of the palms and soles, alopecia, ectropion, nail dystrophy, and ankle edema, with the integument being shiny and hidebound. These changes result in pain on walking and extreme difficulty with tasks requiring manual dexterity. Such patients become cutaneous cripples, severely debilitated by the skin manifestations of this fatal disease. Pruritus is often intense, which results in excoriation, exudation, and secondary infection that may dominate the clinical picture.
HISTOPATHOLOGY
In the patch, plaque, and also in the erythrodermic stage, there is an epidermotropic band-like infiltrate of neoplastic T lymphocytes with hyperconvoluted cerebriform nuclei involving the upper dermis with exocytosis and formation of intraepidermal Pautrier's microabscesses . In the tumor stage a nodular infiltrate in the dermis is found, and the epidermal component is much less pronounced . Immunohistologically the malignant cells express a mature peripheral T-cell (CD4+) phenotype. Partial loss of
pan-T-cell antigens such as CD7 and CD3 may be a feature of MF but is not pathognomic of the disease. Analysis of T-cell receptor genes (TCR) typically shows a clonal rearrangement as demonstrated by PCR or Southern blot techniques.
TREATMENT AND PROGNOSIS
Treatment should be symptom oriented and stage adapted (see Staging of Cutaneous T-Cell Lymphoma and Principles of Treatment of Cutaneous T-Cell Lymphoma later). The prognosis depends on the type and extent of skin involvement (plaques, tumors, or erythroderma), the presence of palpable lymph node involvement, and the presence of visceral disease. Overall, patients with MF limited to the skin have a 5-year survival rate of 80 to 100 percent. In contrast, patients with lymph node involvement show a 5-year survival rate of 40 percent.