Granulomatous slack skin is a rare cutaneous T-lymphoproliferative disease characterized by pendulous skin folds. Histology typically reveals a dermal infiltrate of T cells and multinucleated giant cells showing elastophagocytosis. Specific genetic abnormalities have not yet been identified. Currently, granulomatous slack skin is classified according to the World Health Organization classification as a variant of mycosis fungoides although supporting genetic evidence is yet lacking. We present a well-documented case of a 46-year-old man with the typical histologic and clinical findings of granulomatous slack skin. Cytogenetic analysis of a skin biopsy revealed a t(3;9)(q12;p24) as the sole chromosomal abnormality. Fluorescence in situ hybridization analysis did not reveal involvement of the JAK2 gene, located at chromosome band 9p24, and previously shown to be amplified in Hodgkin lymphoma and primary mediastinal diffuse large B-cell lymphoma. Although more cases have to be reported and the putative oncogene involved in the translocation has yet to be identified, the cytogenetic findings are unlike those described for mycosis fungoides and suggests that granulomatous slack skin is a distinct primary cutaneous T-cell lymphoma.