Hydroa-like cutaneous T-cell lymphoma: a clinicopathologic and molecular genetic study of 16 pediatric cases from Peru.

Hydroa-like cutaneous T-cell lymphoma (hydroa-like CTCL) is an unusual pediatric malignancy with a poor prognosis. An impressive cutaneous rash characterized by edema, blisters, ulcers, crusts, and scars, resembling hidroa vacciniforme, is seen mainly on the face and sometimes on the extremities. The lesion consists of lymphomatous T-cell infiltration of the skin and subcutis with variable exocytosis and angiocentricity. It has been also called edematous, scarring vasculitic panniculitis and hydroa-like lymphoma. An association with Epstein-Barr virus has been suggested. The differential diagnosis includes other cutaneous lymphomas, particularly the cutaneous nasal type T/natural killer-cell lymphoma, mycosis fungoides, precursor T-cell lymphoblastic lymphoma, nonspecific peripheral T-cell lymphoma, cutaneous anaplastic large cell lymphoma, and subcutaneous panniculitic T-cell lymphoma. Other differential diagnoses are inflammatory dermatopathies and panniculitides. Based on a series of 16 such cases referred to the Institute of Neoplastic Diseases, the objective of this report is not only to provide a better clinicopathologic understanding of this entity but also a reappraisal of it as a malignancy. The male/female frequency ratio was 1:1. The median age was 10 years old. All cases showed predominant facial involvement with edema, blisters, ulcers, crusts, and scars. Chemotherapy and/or radiotherapy had little or no benefit. The prognosis was usually dismal. The lymphoma extended from the epidermis to the subcutis, with frequent angiocentric and periadnexal array. Lymphoma cells were mostly of intermediate size with dense hyperchromatic nuclei, inconspicuous nucleoli, and infrequent mitosis. A scanty and variable inflammatory background was found. The lymphoma cells displayed T-cell cytotoxic phenotype. In addition, they were negative for the natural killer cell antigens CD56 and CD57. Epstein-Barr virus in situ hybridization was positive in the six cases in which it was assayed. T-cell receptor gamma (TCRgamma) displayed monoclonal-type rearrangement in four cases studied. Our findings indicate that hydroa-like CTCL is an independent clinicopathologic entity that affects children. Consequently, it should be considered an independent subset of CTCLs and be included as such in the classification of neoplastic diseases of the lymphoid tissues.