progressive transformation of germinal centres progressive transformation of germinal centres progressive transformation of germinal centres (ptgcs) is a reactive lymph node process of undetermined cause. progressive transformation of germinal centresother namesprogressive transformation of germinal centersmicrograph of a lymph node biopsy showing progressive transformation of germinal centres. h&e stain.specialtyinfectious disease signs and symptoms ptgc is usually characterized by localized lymphadenopathy and is otherwise typically asymptomatic. diagnosis micrograph showing ptgcs. h&e stain. ptgc is diagnosed by surgical excision of the affected lymph node(s), and examination by a pathologist. the differential diagnosis includes non-neoplastic causes of lymphadenopathy (e.g. cat-scratch fever, kikuchi disease) and malignancy, i.e. cancer. microscopic appearance ptgcs is characterized by: follicular hyperplasia (many follicles), focally large germinal centres, with poorly demarcated germinal centre (gc)/mantle zone interfaces (as gcs infiltrated by mantle zone lymphocytes), and an expanded mantle zone. treatment ptgc is treated by excisional biopsy and follow-up. it may occasionally recur and a small proportion of patients have been reported to subsequently develop nodular lymphocyte predominant hodgkin lymphoma.