Adult pityriasis lichenoides-like mycosis fungoides: a clinical variant of mycosis fungoides.

BACKGROUND

Mycosis fungoides (MF) is the most frequent type of cutaneous T cell lymphoma. Its clinicopathological spectrum is wide, and the resulting diversity makes it difficult to establish a differential diagnosis among pityriasis lichenoides (PL), lymphomatoid papulosis (LyP), and atypical MF.

OBJECTIVES

This study describes four patients with longstanding PL-like lesions, in whom clinicopathological correlations contributed towards the establishment of definitive diagnoses of MF.

METHODS

The clinical histories of the four patients were reviewed. Skin biopsies were processed by hematoxylin and eosin staining and immunohistochemical techniques. Disease spread was studied according to laboratory tests, complete blood counts, biochemical parameters, lactate dehydrogenase, lymphocyte populations, and Sézary cells. Thoracoabdominopelvic computed tomography was performed.

RESULTS

The four patients included two women and two men, aged 35-70 years, all of whom had chronic skin lesions located mainly on the trunk and extremities. In three patients, initial clinicopathological correlations led to the diagnosis of PL; further biopsies were required to diagnose MF. In all patients, the atypical lymphocytic infiltrate showed a lichenoid or perivascular distribution with focal epidermotropism and parakeratosis. All cases proved positive for CD4 and CD3, and negative for CD20, CD8, and CD30. Polymerase chain reaction showed monoclonal-type T cells in one and polyclonal infiltrates in three patients. All patients were initially treated with topical corticosteroids and photochemotherapy. None of the treatments proved completely successful, but subsequent tests have yielded no evidence of disease progression in any patient.

CONCLUSIONS

In patients with clinical features of longstanding PL and histological findings consistent with MF, differential diagnosis must include PL, LyP, and papular MF. As some forms of PL evolve towards MF and PL-like forms of MF, these patients should undergo regular follow-up and repeated biopsies in order to discard diagnoses of atypical forms of MF.