Role of apoptosis in spontaneous regression of peripheral T-cell lymphoma arising in the skin or subcutis.

ABSTRACT

Apoptosis was suspected to play a significant role in spontaneous regression of skin lesions in four cases of peripheral T-cell lymphoma arising in the skin or subcutis. All of the patients had skin tumors with ulcer formation, but no metastasis to the lymph nodes or viscera. Biopsy showed a sea of CD3-positive lymphoma cells involving the dermis to the subcutis with scattered foci of coagulative necrosis. In the zone of incipient necrosis surrounding the core of coagulative necrosis, frequent apoptotic bodies were identified by electron microscopy (EM), and DNA strand breaks were detected in 34% to 51% (mean, 42%) of lymphoma cells by the TdT-mediated deoxyuridine triphosphate (dUTP)-biotin nick end-labeling (TUNEL). As for the pathogenesis of coagulative necrosis, ischemic necrosis attributable to lymphocytic vasculitis appeared unlikely, because necrotic foci were devoid of neutrophils and had no relation to vascular distribution. Primary cataclysmic apoptosis appeared more likely, but its pathogenetic role could not be established, because EM and TUNEL could not be applied to the core of the debris-ridden coagulative necrosis. Although these cases had been classified as pseudolymphomas because they were histologically malignant but clinically benign, they were in fact true lymphomas characterized by extensive coagulative necrosis with a high rate of apoptosis demonstrable in the zone of incipient necrosis.