A rare case of pemphigus vegetans mimicking malignancy on F-18 FDG PET/CT.

A 42-year-old man with a history of chronic smoking and alcoholism was suspected to harbor a malignancy involving the perioral region and the scalp. He underwent an F-18 FDG PET/CT scan which revealed abnormal F-18 FDG accumulation in the oral mucosa and lips, extending to the nose, scalp, and bilateral cervical lymph nodes. Further work-up ultimately revealed the lesions to be secondary to pemphigus vegetans. Pemphigus vegetans is a rare variant of pemphigus vulgaris, an autoimmune bullous cutaneous disorder and involves mainly the flexural regions of the body. Unlike pemphigus vulgaris, lesions of pemphigus vegetans present as heaped up, eroded, and ulcerative plaques in the intertriginous regions of the body. Occasional lesions may be present on scalp and elsewhere in the Hallopeau variant of the disease. The use of F-18 FDG PET in the field of oncology is rapidly evolving; however, it is not tumor specific. The integration of CT into PET has increased the specificity of this modality. Nevertheless, there are many physiologic and benign conditions that may result in high accumulation of FDG, and may mimic malignancy. Familiarity with F-18 FDG-avid nonmalignant lesions may extend the use of F-18 FDG PET imaging beyond the field of oncology. To the best of our knowledge, this is the first description of PET/CT findings in pemphigus vegetans.