A huge primary adenoid cystic carcinoma of the lung: case report and review of the literature

Primary adenoid cystic carcinoma (ACC) of the lung is a rare tumor, accounting for 0.04–0.2% of all lung tumors. It typically demonstrates slow progression and a propensity for recurrence and relapse. This report describes an unusual radiological presentation of pulmonary ACC and provides a literature review to contextualize its clinical, radiologic, pathologic, and therapeutic aspects.

Pulmonary ACC is a salivary gland-type malignancy that can occur in multiple organs, including the bronchus and lung, and typically shows slow evolution and late metastasis. It reportedly has slight female predominance and no clear risk factors; smoking may paradoxically be protective. Respiratory symptoms are nonspecific, commonly dyspnea, cough, and chest pain. The authors reference work suggesting pulmonary ACC is usually central with longitudinal extension >3 cm and significant luminal wall infiltration. No prior studies or series report a lesion of comparable size to the present case. Histologically, ACC has cribriform, tubular, and solid types; the solid type portends worse prognosis with rapid clinical course and higher metastatic risk, whereas cribriform is less aggressive. Differential diagnoses include carcinoid tumor and adenocarcinoma; immunohistochemistry (lack of TTF1 and neuroendocrine markers such as CD56 and chromogranin) aids diagnosis. Molecular targeted therapy appears ineffective per a small study that found no mutations in common driver genes (EGFR, KRAS, BRAF, ALK, PIK3CA, PDGFRA, DDR2). Surgery is generally the treatment of choice when feasible; the role of radiotherapy is less defined and is often reserved for positive margins or unresectable disease. Prognosis depends on histologic type, TNM stage, and completeness of resection. References include case reports and series, imaging reviews, clinicopathologic analyses, and molecular studies.

Case report of a 50-year-old male farmer (30 pack-year smoker, no TB or cancer family history) with 4 months of dry cough and dyspnea, afebrile, without night sweats or significant weight loss. Exam: dullness to percussion and decreased breath sounds over the left lower lung field. Chest X-ray: opaque left hemithorax with ipsilateral mediastinal shift. Chest CT: large well-limited solid-cystic mass occupying the entire left hemithorax. Hydatid serology negative. Bronchoscopy: endobronchial mass occluding the left upper lobe entrance. Biopsy: cribriform architecture with pseudoglandular cavities filled with mucoid material; tumor cells with rounded hyperchromatic nuclei. Immunohistochemistry: TTF1 negative; features consistent with adenoid cystic carcinoma. Cervicofacial MRI: no primary salivary gland ACC. Staging with PET and brain imaging: solid-cystic left pulmonary process occupying entire left hemithorax, mediastinal lymphadenopathy (right paratracheal and hilar), and hypermetabolic micronodules in the right upper lobe. Staging: T4N3M1a, stage IVa (8th edition TNM). Management: palliative chemotherapy given unresectable stage IVa disease and despite initial performance status 0. After three chemotherapy cycles and 8 months from diagnosis, the patient’s general condition worsened (PS 3); follow-up thoracic CT showed significant decrease in lung mass volume.

- Extremely large solid-cystic pulmonary mass occupying the entire left hemithorax, an unusual radiological presentation not previously reported in size or aspect per the authors. - Endobronchial obstruction of the left upper lobe entrance on bronchoscopy. - Histology confirmed ACC with cribriform pattern; immunohistochemistry negative for TTF1. - Whole-body workup excluded salivary gland primary and revealed mediastinal lymphadenopathy and contralateral upper lobe hypermetabolic micronodules; staged T4N3M1a (stage IVa). - Managed with palliative chemotherapy; after 3 cycles and 8 months, imaging showed a significant reduction in tumor volume, but clinical status declined to PS 3. - Literature emphasizes rarity of pulmonary ACC, central airway predilection, slow progression, diagnostic challenges with potential misclassification as carcinoid or adenocarcinoma, and limited role/evidence for targeted therapies; surgery is preferred when feasible, with variable roles of radiotherapy and chemotherapy.

This case exemplifies the diagnostic and therapeutic challenges of pulmonary ACC, particularly with an exceptionally large, solid-cystic mass occupying an entire hemithorax, which is atypical for reported cases. The clinical presentation was nonspecific, underscoring the need for thorough imaging, endoscopy, and histopathologic assessment. Immunohistochemistry (TTF1 negativity) supported the diagnosis and helped exclude adenocarcinoma and neuroendocrine tumors. Systemic staging established advanced disease (IVa), precluding surgery—the standard of care for localized ACC—and necessitating palliative chemotherapy. Despite radiological response (tumor volume reduction), clinical deterioration occurred, reflecting the complex relationship between tumor burden, airway involvement, and overall functional status in advanced ACC. The literature suggests prognosis is influenced by histologic subtype, stage, and resectability; targeted therapies have not demonstrated efficacy in small series. This case highlights the need to recognize atypical imaging presentations to avoid misdiagnosis and to consider multidisciplinary management strategies in unresectable disease.

Pulmonary ACC is a rare, slow-growing salivary gland-type lung malignancy that can present with atypical radiologic features, including very large solid-cystic masses. Accurate diagnosis relies on histopathology and immunohistochemistry. Surgical resection remains the preferred treatment when feasible; however, advanced disease may require palliative systemic therapy. The unusual radiological presentation in this case further complicates timely diagnosis. Future research should better define the roles of radiotherapy, chemotherapy, and potential molecularly targeted treatments in unresectable or advanced pulmonary ACC.

Single-patient case report limits generalizability. Exact chemotherapy regimen and comprehensive molecular profiling beyond immunohistochemistry are not detailed. Follow-up duration is limited, and clinical outcomes beyond 8 months are not reported. Imaging figures are referenced but the full quantitative measurements of tumor size are not provided in text.