Abstract 1208: Discovery of a previously undescribed cutaneous T-cell neoplasm with chromosomal rearrangements of 6p25.3

Background: Cutaneous T-cell neoplasms display markedly heterogeneous clinical behavior despite often similar pathologic features. For example, transformed mycosis fungoides (tMF) has a poor prognosis and requires intensive therapy whereas lymphomatoid papulosis (LyP) is an indolent lymphoproliferative disorder with spontaneously resolving lesions. These entities have overlapping histologic features and no molecular tools currently exist to aid in subclassification. Methods: We identified 11 T-cell neoplasms with histologic appearances distinct from previously described cutaneous T-cell neoplasms but with features overlapping those of both tMF and LyP. The phenotypic and genetic characteristics of the tumors were studied using immunohistochemistry and fluorescence in situ hybridization, respectively. Clinical data on presentation, treatment, evolution of the lesions, and follow-up were obtained. Results: All patients were older adults (mean age, 75 yr; range, 67-88 yr; 9M:2F). Clinical presentations were similar, with papulonodular skin lesions (0.3-1.0 cm) restricted to a single body area in all but two patients. Histologically there was an extensive atypical lymphoid infiltrate in the epidermis and a dermal tumor containing large transformed cells with numerous mitotic figures and apoptotic bodies. All tumors had a T-cell phenotype and expressed CD30 in both dermal and epidermal components. No case expressed ALK. Most cases had a high proliferative rate (>80%) by Ki67 staining. FISH analysis demonstrated rearrangements of the DUSP22-IRF4 locus on 6p25.3 in all cases. No patient had evidence of systemic disease on imaging studies. In 4 untreated patients, papules began to regress spontaneously a few weeks after presentation, with complete resolution within a month or two. Seven patients were treated with local excision (with or without cryotherapy) or radiotherapy. All non-excised lesions ultimately regressed. All patients were alive at last follow-up (median, 21 mo; range, 7-150 mo). Cutaneous recurrences occurred in 5 patients. At last follow-up only 1 patient had active lesions, which were confined to the presenting site. The remaining 10 patients had been disease-free from 2 to 32 months. Conclusions: Despite pathologic features mimicking an aggressive lymphoma, the benign clinical course observed in all 11 patients suggests these cases represent a newly recognized subtype of LyP. These neoplasms are characterized by 6p25.3 rearrangements, representin