The value of intraoperative diagnosis in cases of synchronous primary lung adenocarcinoma and colorectal carcinoma metastasis

Öztürk Ç., Okcu O.

38th European Congress of Pathology, Stockholm, İsveç, 12 - 16 Eylül 2026, cilt.489, ss.893, (Özet Bildiri)

  • Yayın Türü: Bildiri / Özet Bildiri
  • Cilt numarası: 489
  • Basıldığı Şehir: Stockholm
  • Basıldığı Ülke: İsveç
  • Sayfa Sayıları: ss.893
  • Recep Tayyip Erdoğan Üniversitesi Adresli: Evet

Özet

Background & Objectives: Colorectal carcinoma (CRC) often spreads to the lungs, but not every new pulmonary nodule in a cancer survivor indicates a metastasis. Distinguishing between a recurrence and a second primary lung tumour presents a significant diagnostic challenge. If these lesions are misclassified, it can result in incorrect staging and the omission of potentially curative surgery. This report discusses a rare case in which both a CRC metastasis and a primary lung adenocarcinoma were discovered in different lobes of the same lung simultaneously. Methods: A 72-year-old male with a history of treated rectal cancer (pT3N1b) presented for routine oncological followup. A PET-CT scan revealed two distinct lesions in his left lung. The first, in the upper lobe, was a 20 mm ground-glass nodule with low metabolic activity (SUVmax 1.4), suggesting an indolent process. The second, in the lower lobe, was a 26 mm solid mass showing significant growth and higher activity (SUVmax 3.4). To resolve this discrepancy, surgeons performed wedge resections guided by intraoperative frozen sections. Results: * The Lower Lobe Lesion: Microscopy revealed a "garland-like" growth pattern and "dirty necrosis"—classic hallmarks of intestinal-type spread. Immunohistochemistry (CDX2+/TTF1-) confirmed this as a colorectal metastasis. * The Upper Lobe Lesion: This nodule displayed a "lepidic" growth pattern, using the lung’s own alveolar walls as a scaffold. Lacking any gastrointestinal features and testing positive for TTF1, it was diagnosed as a primary lung adenocarcinoma (Grade 2). Conclusion: This case serves as a critical reminder that we should not automatically label every new lung nodule as a metastasis in patients with a history of cancer. The close correlation between radiological findings (indolent groundglass versus aggressive solid) and histopathology underscores the importance of a personalised approach to each lesion. Using frozen sections and detailed morphological analysis allows clinicians to accurately stage patients and determine the most suitable treatment.