A 68-year-old man with a two-year history of dry cough underwent 18F-fluorodeoxyglucose positron-emission tomography/CT (18F-FDG PET/CT) for the evaluation of lung masses. The results of laboratory tests, which included a complete blood count and determination of serum levels of tumor makers, were unremarkable, except for an elevated serum level of C-reactive protein. The 18F-FDG PET/CT revealed multiple hypermetabolic masses, with scattered internal calcifications, in both lungs (Figure 1A-1C). The maximum diameter was 66 mm, and the standardized uptake value was 4.45. Transbronchial needle aspiration biopsy confirmed the suspected diagnosis of pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma. The patient then received immunotherapy, and a follow-up CT scan showed that the mass decreased in size, although the calcifications remained unchanged (Figure 1D).

The most common diagnosis for a pulmonary mass with internal calcification is granuloma. The differential diagnoses include hamartoma, carcinoid, metastasis, and primary bronchogenic carcinoma.(1) However, calcification is rarely observed in lymphoma. It is almost always associated with previous treatment, including radiation and chemotherapy. (2) Calcification in untreated pulmonary MALT lymphoma has rarely been described in the literature, and the underlying mechanism is unknown. The FDG-avid nature of the lesion described here might be due to its large size.(3) In patients presenting with a hypermetabolic lung mass with scattered internal calcifications on 18F-FDG PET/CT, the differential diagnosis should include MALT lymphoma.

REFERENCES

1. Amin SB, Slater R, Mohammed TL. Pulmonary calcifications: a pictorial review and approach to formulating a differential diagnosis. Curr Probl Diagn Radiol. 2015;44(3):267-276. https://doi.org/10.1067/j.cpradiol.2014.12.005
2. Suzuki L, Funari M, Rocha Mde S, Cristofani LM, Odone Filho V, Vieira GS. Calcification in primary lung non-Hodgkin lymphoma. Rev Hosp Clin Fac Med Sao Paulo. 1995;50(4):227-229.
3. Albano D, Borghesi A, Bosio G, Bertoli M, Maroldi R, Giubbini R, et al. Pulmonary mucosa-associated lymphoid tissue lymphoma: 18F-FDG PET/CT and CT findings in 28 patients. Br J Radiol. 2017;90(1079):20170311. https://doi.org/10.1259/bjr.20170311