Amyloidosis is a protein-folding disease that results in the deposition of misfolded proteins into various tissues of the body, resulting in dysfunction of the affected organ. It is caused by a heterogeneous group of disorders caused by extracellular deposition of misfolded proteins as insoluble fibrils. Involvement of the lungs can present as nodular, tracheobronchial, or diffuse interstitial, and can be mistaken for cancer or infection on imaging. The combination of Sjögren's syndrome, chronic activation of B cells, and the risk of developing a lymphoproliferative disorder can lead to the rare deposition of amyloid. In cystic lung disease, the amyloid deposition can be misattributed to lymphoid interstitial pneumonia (LIP). An evaluation for progressive dyspnea and chest pain was done in a 68-year-old female patient diagnosed with Sjögren's syndrome and severe degenerative aortic valve disease (severe double aortic lesion). The patient's high-resolution computed tomography scan demonstrated diffuse pulmonary cysts of the thin-walled variety that are consistent with a pattern of LIP, with several solid nodules layered on top of each other exhibiting increased attenuation, as well as some that are calcified on the mediastinal windows. An October 2023 core lung biopsy revealed structures resembling bony spicules with dystrophic calcification and an adjacent amorphous area that lacked cells; malignancy was absent. Microbiological studies were negative for bacteria, fungi, and mycobacteria, and there were no malignant cells in the cytology. The patient's autoimmune testing revealed rheumatoid factor at 20.2 IU/mL, as well as anti-Ro (SSA) 125 and anti-La (SSB) 79.9. Sjögren's syndrome was confirmed by a salivary gland biopsy. Re-reviewing archived biopsy material in 2025 showed that the unexplained nodules still had atypical radiographic characteristics, with the Belizean red stain showing polarized light birefringence, confirming the presence of pulmonary amyloid. The functional assessment showed a 6-minute walk distance of 392 m with an oxygen saturation nadir of 85% at minute 4. Right heart catheterization with fluid challenge (August 2025) showed a mean pulmonary artery pressure of 24 mmHg, pulmonary artery wedge pressure rising from 12 to 18 mmHg, hypothesized cardiac output of 5.1 L/min, cardiac index 3.6 L/min/m², and pulmonary vascular resistance of 2.3 Wood units, consistent with mild pulmonary hypertension and a post-capillary contribution with severe aortic valve disease. The patient continues to be managed by a multidisciplinary team, with no systemic amyloidosis documented to date. When pulmonary nodules co-exist with Sjögren's syndrome, pulmonary amyloidosis, although rare, should be considered, especially when the syndrome co-exists with cystic changes that suggest LIP. Persistent atypical changes in radiology and biopsy should trigger a more thorough examination of stale biopsies. Secondary severe valve disease, augmenting pulmonary hypertension, should be an impetus for ongoing multidisciplinary care and a thorough ongoing assessment.

Cystic lung lesions and diseases represent a wide range of entities that are challenging for radiologists to diagnose. This difficulty arises from ambiguous terminology, similar imaging appearances, and the frequent coexistence of multiple disease entitiesTo describe a comprehensive, step-wise algorithm enabling radiologists to accurately describe cystic lung lesions and support the correct diagnosis of diseases presenting with lung cysts or cyst-like findings.A refined diagnostic algorithm is proposed based on the authors' clinical experience and a comprehensive literature search (PubMed).Our recommended approach to cystic lung lesions guides radiologists through three key steps: (1) Confirmation whether a lesion meets the definition of a true pulmonary cyst (thin-walled ≤ 2mm, well-circumscribed, air-containing structure) and distinguishing true cysts from mimicking lesions; (2) Evaluation of possible etiologies: congenital, inflammatory, senescent, neoplastic, diffuse cystic lung diseases; and (3) Identification of diffuse cystic lung diseases (DCLDs) including lymphangioleiomyomatosis, Birt-Hogg-Dubé syndrome, pulmonary Langerhans cell histiocytosis, lymphoid interstitial pneumonia, light-chain deposition disease, and neurofibromatosis type 1, using key CT features and associated thoracic and extra-thoracic findings.Radiologists should be familiar with cystic lung lesions and their common mimics to ensure accurate classification. The spectrum of cases is broad, ranging from congenital, to age-related and neoplastic as well as diffuse cystic lung diseases. A clear and step-wise approach assists radiologists in addressing cystic lung lesions and DCLDs and thus improves clinical decision-making and patient management. · Differentiation between true lung cysts and mimicking lesions.. · Assessment of a broad spectrum of etiologies of cystic lung lesions.. · Diagnosis of diffuse cystic lung diseases.. · Radiologists should be familiar with the terminology of cystic lung lesions to reduce ambiguity in reports, thereby improving communication with clinicians.. · Following a step-wise structured approach to cystic lung lesions and their mimics can contribute to safer radiological diagnoses.. · Recognizing specific radiologic patterns in cystic lung diseases facilitates diagnosis and, when necessary, timely referral for multidisciplinary evaluation.. · Martin Mens A, Andreisek G, Müller MA. Cystic lung diseases in the daily routine: a comprehensive step-wise algorithm for the radiological diagnosis of cystic lung lesions and diffuse cystic lung diseases. Rofo 2026; DOI 10.1055/a-2804-9147. Zystische Lungenläsionen und -erkrankungen umfassen eine Vielzahl von Krankheitsbildern, die für Radiologen eine diagnostische Herausforderung darstellen. Das liegt unter anderem an einer uneinheitlichen Nomenklatur, ähnlichen Erscheinungsbildern sowie der Koexistenz verschiedener Erkrankungen.Ziel ist die Vorstellung eines umfassenden, schrittweisen Algorithmus, der Radiologen eine präzise Beschreibung zystischer Lungenläsionen ermöglicht und zur korrekten Diagnose von Erkrankungen, die mit Lungenzysten oder zystenähnlichen Erscheinungen einhergehen, beiträgt.Auf Grundlage der persönlichen Erfahrungen der Autoren und einer umfassenden Literaturrecherche (PubMed) wird ein verfeinerter Diagnosealgorithmus vorgeschlagen.Der vorgeschlagene Ansatz umfasst drei zentrale Schritte: (1) Überprüfung, ob die Definition einer echten Lungenzyste erfüllt ist (dünnwandig ≤2 mm, scharf abgegrenzt, luftgefüllte Struktur) und Unterscheidung zwischen echten Zysten und zystenähnlichen Läsionen; (2) Evaluierung verschiedener Ätiologien: angeborene, entzündliche, altersbedingte, neoplastische, diffuse zystische Lungenerkrankungen; und (3) Identifikation diffuser zystischer Lungenerkrankungen (DCLDs) wie Lymphangioleiomyomatose, Birt-Hogg-Dubé-Syndrom, pulmonale Langerhans-Zell-Histiozytose, lymphoide interstitielle Pneumonie, Leichtketten-Ablagerungskrankheit und Neurofibromatose Typ 1 unter Verwendung wichtiger CT-Merkmale und assoziierter thorakaler und extrathorakaler Befunde.Radiologen sollten mit zystischen und morphologisch ähnlichen Lungenläsionen vertraut sein, um eine korrekte Klassifizierung der Befunde zu ermöglichen. Die Ursachen reichen von angeborenen über altersbedingte bis hin zu neoplastischen und diffusen zystischen Lungenerkrankungen. Ein klarer und schrittweiser Ansatz unterstützt Radiologen bei der Beurteilung zystischer Lungenläsionen und -erkrankungen und verbessert so die klinische Entscheidungsfindung und das Patientenmanagement. · Unterscheidung zwischen echten Lungenzysten und mimetischen Läsionen. · Bewertung eines breiten Spektrums von Ätiologien zystischer Lungenläsionen. · Diagnose diffuser zystischer Lungenerkrankungen. · Radiologen sollten mit der Terminologie zystischer Lungenläsionen vertraut sein, um Unklarheiten in den Befunden zu reduzieren und die Kommunikation mit den Klinikern zu verbessern.. · Ein schrittweiser, strukturierter Ansatz bei zystischen und zystenähnlichen Lungenläsionen kann zu sichereren radiologischen Diagnosen beitragen.. · Das Erkennen spezifischer radiologischer Muster bei zystischen Lungenerkrankungen erleichtert die Diagnose und ermöglicht bei Bedarf eine rechtzeitige Überweisung zur multidisziplinären Beurteilung..

A woman in her 50s was referred by her general practitioner to the Emergency department for workup of mild hyponatraemia. Her background was significant for an established diagnosis of primary Sjogren's syndrome (pSS), and she was attending a rheumatologist regularly. Further investigations undertaken to establish the cause of her hyponatraemia included CT of the thorax, abdomen and pelvis, which revealed multiple ground glass opacities mostly in the lower lobes. CT-guided biopsy of the lesion in the left lower lobe revealed cores of lung parenchyma with chronic lymphoplasmacytic infiltration and fibrosis. Her case was discussed at the lung multidisciplinary meeting (MDM), and the consensus opinion was a diagnosis of Lymphocytic Interstitial Pneumonia (LIP) based on clinical, radiological and histological evidence. This case illustrates markedly abnormal radiological findings of LIP in a patient with pSS who has remained asymptomatic after a 2 year period of clinical, radiological and physiological monitoring.