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Skin Cancer Cutaneous T-cell Lymphoma Hematology and pathology

Mycosis fungoides and the Sezary syndrome are cutaneous T-cell lymphomas. These are characterized by the expansion of a clone of malignant CD4 helper T-cells that have a propensity to home and accumulate in the skin, lymph nodes, and peripheral blood.

Confirming the diagnosis of mycosis fungoides is difficult in the early stages of the disease. The clinician will biopsy patch stage lesions and ask the pathologist to rule out MF. The classic features of the disease are usually absent at this stage. Typically a few atypical lymphocytes are seen and the pathologist reports an atypical lymphocytic infiltrate, suspicious for MF.

Biopsy in patch-or-plaque stage shows a lymphocytic infiltrate in the superficial dermis, with individual lymphocytes migrating among epidermal keratinocytes. The affinity of the malignant T-cells to migrate to the epidermis is called epidermotropism.

The lymphocytes are pleomorphic, hyperchromatic, and have hyperconvoluted nuclei.

Staining of skin-biopsy specimens with a panel of lymphocyte markers is used sub classify the clone of cells. Immunohistochemistry and molecular genetics have demonstrated aberrant expression of the T lymphocyte surface antigens. The neoplastic T helper CD4 positive cells show gene rearrangements of the T cell receptors, usually of the alpha/beta receptors.

Biopsys taken at different times and locations and other special studies are all used in an attempt to make a diagnosis and determine prognosis.