In situ identification and enumeration of T lymphocytes in cutaneous T-cell lymphomas by demonstration of granular activity of acid non-specific esterase.

Activity of acid non-specific esterase (ANAE) in infiltrating lymphocytes in nine patients with mycosis fungoides and four patients with parapsoriasis en plaques was examined in frozen tissue sections. Within the dermal infiltrate 81.7 +/- 6.1% of all lymphocytes contain this enzyme in mycosis fungoides, 74.7 +/- 3.3% in parapsoriasis en plaques. These results correlate well with the percentage of T lymphocytes determined by immunological techniques. Mycosis fungoides may be regarded as an ANAE-positive cutaneous T-cell lymphoma. Because of its simplicity this technique may be of value in further investigations of mycosis fungoides.