PERIPHERAL T-CELL AND NATURAL KILLER CELL NEOPLASMS
Peripheral T-cell lymphoma,
unspecified is a “wastebasket” diagnostic category.
Adult T-cell leukemia/lymphoma
(ATLL) is a malignant T-cell disorder (CD4-T cells) due to HTLV-1 infection. It
is often seen in Japan and the Caribbean. Clinical symp-toms include skin
lesions, hypercalcemia, enlarged lymph nodes, heptomegaly, and splenomegaly.
Microscopically, characteristic hyperlobated “4-leaf clover” lympho-cytes can
be found in the peripheral blood.
Mycosis fungoides is a malignant
T-cell disorder (CD4+ cells) that has a better prognosis than ATLL. It can
present with a generalized pruritic erythematous rash (no hypercalcemia), which
develops as a sequence of skin changes:
inflammatory eczematous stage →
plaque stage → tumor nodule stage
PAS-positive lymphocytes are present in the epidermis (epidermotropism);
aggregates of these cells are called Pautrier microabscesses. If there is
erythroderma and cerebriform Sézary cells are present in peripheral blood, the
condition is called Sézary syndrome.