Cutaneous lymphomas are rare in young patients and are mostly represented by mycosis fungoides and its variants and CD30+ lymphoproliferative disorders (lymphomatoid papulosis [LYP] and anaplastic large T-cell lymphoma). We report our observations in a series of 69 patients less than 20 years of age who presented either with primary cutaneous lymphoma (n = 62) or with secondary manifestations of extracutaneous disease (n = 7). Clinicopathologic features permitted classification of the cases into the following diagnostic categories: mycosis fungoides (n = 24, all primary cutaneous), anaplastic large T-cell lymphoma (n = 13, all primary cutaneous), LYP (n = 11, all primary cutaneous), subcutaneous "panniculitis-like" T-cell lymphoma (n = 1, primary cutaneous), small-medium pleomorphic T-cell lymphoma (n = 2, all primary cutaneous), natural killer (NK)/T-cell lymphoma, nasal-type (n = 1, secondary cutaneous), follicle center cell lymphoma (n = 1, primary cutaneous), marginal zone B-cell lymphoma (n = 7, all primary cutaneous), B-lymphoblastic lymphomas (n = 6, 3 primary and 3 secondary cutaneous), specific cutaneous manifestations of Hodgkin disease (n = 1, secondary cutaneous), and acute myeloid leukemia (n = 2, both secondary cutaneous). Cutaneous lymphoma in children should be differentiated from benign skin disorders that may simulate them. In particular, mycosis fungoides and LYP in this age group may present with clinicopathologic features reminiscent of inflammatory disorders such as pityriasis alba, vitiligo, pityriasis rosea, and pityriasis lichenoides et varioliformis acuta. Even in secondary cutaneous lymphomas, skin manifestations may be the first sign of the systemic disease, and a diagnosis may be achieved on examination of histopathologic specimens of a cutaneous lesion. Our study illustrates the wide spectrum of cutaneous lymphomas and leukemias in patients less than 20 years of age and underlines the need for proper interpretation of these lesions by dermatologists and dermatopathologists.

Lymphomatoid papulosis (LyP) is a recurrent, self-healing eruption belonging to the spectrum of cutaneous CD30+lymphoproliferative disorders. Three main histologic subtypes of LyP are recognized: type A (histiocytic), type B (mycosis fungoides-(MF)-like), and type C (anaplastic large cell lymphoma-like). We reviewed 26 biopsies from 9 patients (M:F=6:3, median age: 29; mean age 27,2; age range 10 to 38) who presented with clinical features typical of LyP but with histopathologic aspects that resembled primary cutaneous aggressive epidermotropic CD8+cytotoxic T-cell lymphoma. In all but 1 case atypical lymphoid cells showed expression of CD30, and in 8 of 9 cases a T-cell cytotoxic phenotype could be observed (betaF1+, CD3+, CD4-, CD8+). Expression of at least 1 cytotoxic marker (TIA-1, granzyme B) was observed in all cases. Polymerase chain reaction analysis of the T-cell receptor genes revealed a monoclonal rearrangement in 2 of 5 cases tested. Follow-up data available for 8 patients (mean follow-up time: 84 mo, median: 32.5 mo; range: 1 to 303 mo) revealed that none of them developed systemic involvement or signs of other cutaneous lymphomas. This cytotoxic variant of LyP may be histopathologically indistinguishable from primary cutaneous aggressive epidermotropic CD8+ cytotoxic T-cell lymphoma, and may be the source of pitfalls in the diagnosis and classification. We propose the term LyP type D for this unusual variant of the disease. Accurate clinicopathologic correlation is required in this setting, with crucial implications regarding prognosis and management of patients.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a neoplasm derived from precursors of plasmacytoid dendritic cells. Cutaneous involvement represents often the first manifestation of the disease. We studied 45 skin biopsies from 33 patients (M:F=7.25:1; median age: 71 y; age range: 30 to 89) with BPDCN to delineate histopathologic and immunophenotypic features of this disease. Patients presented with generalized (n=18), localized (n=6), or solitary (n=9) macules, plaques, and/or tumors. Staging investigations at presentation were negative in 20 patients. Unusual histologic features included a perivascular/periadnexal pattern (6 biopsies from 4 patients) and the presence of pleomorphism of neoplastic cells with blastoid cells admixed with elongated, twisted, or hyperchromatic cells (observed in 24 specimens). Negativity of 1 among the 4 markers CD4, CD56, CD123, and TCL-1 was seen in 11 biopsies, and of 2 markers in 4 biopsies. Staining for CD68 revealed positivity of the majority of cells in 1 and of scattered cells in 24/37 stained cases. Terminal deoxynucleotidyl transferase was observed in 22/37 stained cases. Staining for Bcl-6, MUM-1 and FOX-P1 revealed positivity of a variable proportion of neoplastic cells in 16/30, 19/29, and 21/23 cases, respectively. Our study shows that cutaneous lesions of BPDCN display a greater variability of morphologic and phenotypic features than recognized earlier. Discrete perivascular infiltrates, pleomorphic morphology of neoplastic cells, and unusual phenotypic profiles may be the source of diagnostic pitfalls. These atypical variants should be recognized to make an early diagnosis and to manage properly patients with this aggressive hematological disorder.

Classification of primary cutaneous lymphomas (PCLs) is the subject of ongoing controversy. Based on a series of 556 patients, the applicability of the European Organization for Research and Treatment of Cancer (EORTC) classification for PCLs was assessed and compared to the proposed World Health Organization (WHO) classification of hematologic malignancies. The large majority of patients could be properly classified according to the scheme proposed by the EORTC. Comparison of estimated 5-year survival for specific diagnostic categories of PCLs demonstrated nearly complete concordance of the present results with those of the EORTC study for most of the indolent cutaneous T-cell lymphomas and cutaneous B-cell lymphomas, whereas differences were found for mycosis fungoides-associated follicular mucinosis and Sezary syndrome. A few patients with newly described entities (CD8(+) epidermotropic cytotoxic T-cell lymphoma, primary cutaneous natural killer/T-cell lymphoma) could not be classified according to the EORTC scheme. Comparison of the EORTC with the WHO classification showed that the EORTC scheme allows a more precise categorization of the patients, especially for cutaneous B-cell lymphoma. In conclusion, the study confirmed that the EORTC classification allows a better management of patients with PCL. Small amendments to that classification should be carried out to account for recently described entities and to unify some of the diagnostic categories.

The predominance of dermoscopic types of melanocytic naevi varies according to the individual's age. Awareness of the age-related dermoscopic predominance of melanocytic naevi might allow more accurate recognition of dermoscopic patterns of melanocytic skin lesions that are unusual with respect to the individual's age. This observation may help in the early recognition of some 'banal'-appearing melanomas. Furthermore, the observations made in this study raise interesting questions regarding naevus evolution.