Histology
The criteria for the disease are established on the skin biopsy by the presence of the following:
Presence of cancer cells with twisted contours (cerebriform nuclei)
In the patch and plaque stages, the cancer cells are seen in the epidermis (the most superficial layer of skin). This is referred to as epidermotropism. Pautriers microabcesses, aggregates of four or more atypical lymphocytes arranged in the epidermis. Pautrier microabcesses are characteristic of mycosis fungoides but are generally absent. In the tumour stage, the cancer cells move into the dermis (the deeper layer of skin)
Large cell transformation, where clonally identical lymphocytes in the lesion exhibit hypertrophy. In transformed cells, presence of the CD30 receptor is associated with improved survivalTo stage the disease, various tests may be ordered, to assess nodes, blood and internal organs, but most patients present with disease apparently confined to the skin, as patches (flat spots) and plaques (slightly raised or wrinkled spots). Peripheral smear will often show buttock cells. Staging
Traditionally, mycosis fungoides has been divided into three stages: premycotic, mycotic and tumorous. The premycotic stage clinically presents as an erythematous (red), itchy, scaly lesion. Microscopic appearance is non-diagnostic and represented by chronic nonspecific dermatosis associated with psoriasiform changes in epidermis.In the mycotic stage, infiltrative plaques appear and biopsy shows a polymorphous inflammatory infiltrate in the dermis that contains small numbers of frankly atypical lymphoid cells. These cells may line up individually along the epidermal basal layer. The latter finding if unaccompanied by spongiosis is highly suggestive of mycosis fungoides.
It is hypothesized that the genetic mutations in these cancer cells lead to increased growth and escape from programmed cell death.Additionally, the disease is an unusual expression of CD4 T cells, a part of the immune system. These T cells are skin-associated, meaning they are biochemically and biologically most related to the skin, in a dynamic manner. Mycosis fungoides is the most common type of cutaneous T-cell lymphoma (CTCL), but there are many other types of CTCL that have nothing to do with mycosis fungoides and these disorders are treated differently. Diagnosis
Diagnosis often requires a combination of clinical and pathological studies. Diagnosis is sometimes difficult because the early phases of the disease often resemble inflammatory dermatoses (such as eczema, psoriasis, lichenoid dermatoses including lichen planus, vitiligo, and chronic cutaneous lupus erythematosus), as well as other cutaneous lymphomas. Several biopsies are recommended, as the key microscopic features are often absent in early MF, and a complete diagnosis requires a combination of clinical and histological study. Furthermore, long periods of treatment can alter the biopsy findings, making it difficult to distinguish from other inflammatory dermatoses. Childhood Mycosis fungoides (MF) makes up 0.5% to 7.0% of cases. Although data on childhood MF is limited, a 2021 systematic review observed that there is a significant delay in the diagnosis of childhood MF which may negatively affect a child’s prognosis. Notably, most pediatric persons with MF present with early-stage disease.