Follicular Lymphoma Presenting as Refractory Panniculitis-like Lesions: A Case Report of Successful Salvage with Autologous Stem Cell Transplantation

Background: Follicular lymphoma can be difficult to diagnose when extranodal manifestations, particularly cutaneous lesions, mimic inflammatory disease. Case Presentation: We report the case of a 52-year-old man with type 2 diabetes mellitus who presented with marked unintentional weight loss, iron deficiency anemia, elevated inflammatory markers, an approximately 100 mm bundle-like infiltration of the mesenteric adipose tissue, and panniculitis-like scalp lesions. Initial gastroenterological evaluation did not reveal malignancy. Biopsy of a cutaneous lesion showed a lobular lymphocytic infiltrate without evidence of malignancy, and IgG4-related mesenteric panniculitis was suspected. Despite treatment with colchicine, corticosteroids, and sequential immunosuppressive therapy, the cutaneous and subcutaneous lesions progressed. Re-evaluation revealed cervical lymphadenopathy, and histopathological examination of an excised lymph node established the diagnosis of grade 3A FL. Staging 18F-FDG PET/CT showed cervical and supraclavicular nodal disease, involvement of the nasal cavity and nasopharynx, and hypermetabolic cutaneous lesions. Six cycles of R-CHOP produced a partial metabolic response, with residual FDG-avid extranodal disease. Repeat biopsy confirmed persistent FL without evidence of large B-cell transformation. The patient subsequently received platinum- and cytarabine-based salvage chemotherapy and radiotherapy to the residual disease sites, followed by autologous stem cell transplantation after R-BEAM conditioning. On day +100 after transplantation, PET/CT showed complete metabolic remission, and the cutaneous lesions had healed. Conclusions: This case demonstrates that systemic FL may mimic mesenteric panniculitis and inflammatory skin disease. Persistent panniculitis-like lesions that do not respond to immunosuppressive treatment should prompt diagnostic reassessment, repeat biopsy, and careful clinicopathological correlation.