Atypical Histiocytic Lesion Preceding a Peripheral T-Cell Lymphoma Involving the Skin Exhibiting the Same Molecular Alterations.

Peripheral T-cell lymphoma (PTCL), not otherwise specified (NOS) is a diagnosis of exclusion, showing extreme cytological and phenotypic heterogeneity. Skin involvement of PTCL may be primary or secondary. Diagnosis of histiocytosis may be difficult, requiring clinical-pathological correlation. We describe a laryngeal atypical histiocytic lesion (AHL) and a nasal PTCL, NOS with cutaneous involvement in the same patient presenting with peculiar histopathologic and immunophenotypic features. The laryngeal neoplasm showed morphological and immunophenotypic evidence of histiocytic differentiation and does not fit any other category of the WHO classification nor the revised classification of histiocytosis. The nasal and cutaneous lesions presented features close to natural killer/T-cell lymphoma and gamma-delta T-cell lymphoma but did not meet accurately the WHO criteria. A somatic activating Q61K mutation was found on exon 3 of the NRAS gene in both AHL and PTCL, NOS. The mutation on NRAS gene in both AHL and PTCL, NOS may suggest a common origin from a precursor cell.