Role of PET imaging in peritoneal involvement of subcutaneous panniculitis-like T-cell lymphoma.

Subcutaneous panniculitis-like T-cell lymphoma is a rare subtype of cutaneous T-cell lymphomas and represents less than 1% of non-Hodgkin's lymphomas. Currently, the diagnosis is based on clinical and histological findings although clinical features may be nonspecific. Often, it is localised to subcutaneous tissue without lymph node involvement. The literature is sparse but unusual presentations have been described to involve mesentery, breast and even eyelids. Fluorine-18 fluorodeoxyglucose positron-emission tomography/computed tomography has been reported to be useful in assessing disease activity, extent and treatment response in subcutaneous panniculitis-like T-cell lymphoma but we find that it can also be a diagnostic aid for atypical presentations. In our case report, we describe a patient who presented with a neck lump but did not have any other obvious cutaneous lesions. This was biopsied and had histological features in keeping with subcutaneous panniculitis-like T-cell lymphoma. Due to the atypical presentation, positron-emission tomography was crucial for detecting the extracutaneous and likely primary site of disease in the peritoneum, which hence guided the subsequent biopsy to this affected area and confirmed the diagnosis.