Correct answer : a
The condition described in question is Mycosis fungoides (MF)
It is a variant of cutaneous T-cell lymphoma.
The most important histologic feature of MF is the presence of lymphocytes in the epidermis (epidermotropism).
In late stages, the dermal infiltrate becomes dense to the point of forming tumor nodules. Sézary syndrome refers to the systemic dissemination of MF.
Cluster of differentiation (CD) antigens are cell surface molecules that serve as useful markers of cellular identity.
Currently some 300 different molecules have been assigned CD numbers.
CD4 is a useful marker of helper T lymphocytes.
None of the other choices are T-cell markers.