PMC9842888_01
Chest computed tomography image demonstrating a solid nodule (arrow) measuring 21 x 20 mm in diameter in the superior segment (S6) of the left lower lobe.
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A 42-year-old man was diagnosed with rectal cancer (cT2N2bMx [UICC 8th edition]) with a solid nodule measuring 21 x 20 mm in diameter at the superior segment (S6) of the left lower lobe on the chest computed tomography (Fig. 1).
Histopathological findings of the lung tumor and rectal adenocarcinoma (200 x magnification). Hematoxylin-eosin staining of the lung tumor sample demonstrated columnar epithelial cancer cells consisting of tubular structures (a) that resembled rectal adenocarcinoma (i). Thyroid transcription factor-1 (TTF-1) was positive in both the lung (b) and rectal adenocarcinoma samples (j). Further results of immunohistochemistry were as follows: the lung tumor sample was napsin A (-) (c), cytokeratin 7 (CK7) (-) (d), cytokeratin 20 (CK20) (+) (e), Caudal-related homeobox transcription factor 2 (CDX2) (weakly +) (f), special AT-rich sequence binding protein 2 (SATB2) (+) (g) and beta-catenin (+) (h); the rectal adenocarcinoma sample was napsin A (-) (k), CK7 (-) (l), CK20 (partly +) (m), CDX2 (weakly +) (n), SATB2 (+) (o), and beta-catenin (+) (p).
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Hematoxylin-eosin staining of the lung tumor demonstrated columnar epithelial cancer cells consisting of tubular structures (Fig. 2a); these morphologies resembled rectal adenocarcinoma (Fig. 2i). SPT24, Novocastra, San Ramon, CA, USA) was positive in the lung tumor sample (Fig. 2b), prompting us to retrospectively review the rectal adenocarcinoma specimen. Surprisingly, TTF-1 was also positive in the rectal adenocarcinoma specimen (Fig. 2j). Further results of IHC were as follows: the lung tumor sample was napsin A (-) (clone: IP64, Novocastra, San Ramon, CA, USA), cytokeratin 7 (CK7) (-) (clone: SP52, Ventana, Tucson, AZ, USA), cytokeratin 20 (CK20) (+) (clone: SP33, Ventana, Tucson, AZ, USA), Caudal-related homeobox transcription factor 2 (CDX2) (weakly +) (clone: CDX2-88, Biocare Medical, Pacheco, CA, USA), special AT-rich sequence binding protein 2 (SATB2) (+) (clone: EPNCIR130A, abcam, Cambridge, UK), and beta-catenin (+) (clone: 17C2, Leica Biosystems Newcastle Ltd, Newcastle, UK) (Fig. 2c-h); the rectal adenocarcinoma sample was napsin A (-), CK7 (-), CK20 (partly +), CDX2 (weakly +), SATB2 (+), and beta-catenin (+) (Fig. 2k-p).