Idiopathic cervical fibrosis is a rare tumefactive inflammatory-sclerosing lesion involving the soft tissues of the head and neck, and a proportion of patients also have synchronous or metachronous inflammatory fibrosclerosing lesions in other anatomic sites. The latter finding suggests that this entity may represent a member of IgG4-related sclerosing diseases. We report 4 cases to support this postulation. The patients were male adults aged 42 to 89 years, who presented with an infiltrative, firm cervical mass. Two patients also had IgG4-related chronic sclerosing sialadenitis of submandibular gland and lymphadenopathy. Histologically, the cervical soft tissue lesions had ill-defined borders, consisting of coalescent nodular lymphoid aggregates accompanied by a sclerotic stroma. Nerve infiltration, skeletal muscle invasion, and phlebitis were present. There was a significant increase in IgG4 plasma cells (87 to 327 per high-power field, with IgG4/IgG ratio of 63% to 98%). In the soft tissue lesion of 1 patient, there were expansile foci comprising dense sheets of plasma cells and small lymphoid cells that exhibited κ light chain restriction and clonal immunoglobulin gene rearrangement, consistent with supervening extranodal marginal zone lymphoma. The adjacent lymph node from the same patient showed Epstein-Barr virus (EBV)-positive classical Hodgkin lymphoma with typical morphology and immunophenotype (CD30, CD15, PAX5). Thus lymphoma can supervene in the chronic inflammatory background similar to that recently documented for IgG4-related sclerosing disease of the ocular adnexa.