Unilateral non-Hodgkin's lymphoma of the frontal sinus presenting as Pott's puffy tumour.

Malignant lymphoma of the paranasal sinuses and nasal cavity is very rare and can mimic those of infectious, non-lymphomatous neoplastic and granulomatous process in their initial presentation, thus delaying its diagnosis. This report describes a case of unilateral frontal sinus B-cell lymphoma presenting as Pott's puffy tumour. Key features to differentiate the two conditions are discussed. A 61-year-old woman presented with 4 weeks history of a gradually enlarging right-sided forehead swelling, which was smooth and firm with no tenderness, fluctuation or overlying skin changes. Initial computed tomography (CT) of the paranasal sinuses revealed a mildly opacified right frontal sinus with an overlying soft tissue swelling. A repeat CT scan one week later showed evidence of osteomyelitis of the medial wall of the right frontal bone and orbit, suggesting diagnosis of Pott's puffy tumour. A third CT scan was performed as the swelling continued to enlarge despite antibiotics, which demonstrated a collection over the frontal sinus. No pus was found from a frontal sinus trephine. Histopathologic analysis of the frontal sinus biopsy showed diffuse large B cell lymphoma. The patient was treated successfully with 6 cycles of chemotherapy. In conclusion, it is not easy to differentiate Pott's puffy tumour from frontal sinus lymphoma at their initial presentation. With clearer understanding of both conditions, we can raise the index of suspicion among clinicians of the possibility of frontal sinus lymphoma even when evidence of osteomyelitis is present, therefore prompting earlier tissue biopsies for confirmation of diagnosis.