Metastatic lung adenocarcinoma presenting as diminutive colonic polyp

We present a rare case of adenocarcinoma of lung metastatic to the colon. A 67-year-old woman was referred for colonoscopy for new onset iron deficiency anemia and occult blood in the stool. Colonoscopy showed a 3-mm polyp in the cecum (Figure 1A). Polypectomy was performed. Histopathology revealed poorly differentiated lung adenocarcinoma undermining colonic mucosa (Figure 1B). The cells were positive for CK7, AE1/AE3, and TTF-1 (focal), while negative for CK20, CDX-2, S-100 protein, and CD117 consisted with adenocarcinoma of the lung. A CT scan revealed a lobulated left lower lobe pleural-based mass measuring 4.1 cm × 5.6 cm (Figure 1C). Of note, her past medical history was significant for stage IIIA right lung adenocarcinoma diagnosed 13 years prior to the presentation and treated by right upper lobectomy and adjuvant chemoradiation therapy. Palliative chemotherapy was initiated for the patient.

Figure 1 A rare case of adenocarcinoma of lung metastatic to the colon. (A) Polyp in cecum; arrow indicates polyp; (B) histological findings showing adenocarcinoma (hematoxylin and eosin stain; magnification 100×); arrows indicate adenocarcinoma; (C) CT scan showing pleural based mass; arrow indicates mass.

Metastatic disease to the colon from an extracolonic primary malignancy is very rare. In a large multicenter European study of 10,365 patients with colorectal malignant tumors, there were 35 patients found to have metastasis to colon from an extracolonic primary (1). The most common primary sites were breast (17 cases) and melanoma (7 cases). The other sites were lung, osteosarcoma, leiomyosarcoma, clear cell carcinoma of kidney and Merkel cell carcinoma of skin. Most of the cases presented as large colonic masses with intestinal obstruction, perforation or lower gastrointestinal bleed. All patients had died from widely disseminated disease with a mean survival time of 10.67 months (range, 1–41 months).

Up to 50% lung cancers have distant metastases at time of diagnosis (2). The most common sites are brain, liver, adrenal glands and bone (3). Only 14 cases of lung cancer with metastases to colon were described of which 10 were squamous cell cancers, 2 were small cell cancers, 1 adenocarcinoma and 1 large cell cancer of lung (4). Our patient has adenocarcinoma of lung presenting as diminutive colonic polyp which was not reported before. The diagnosis was aided by use of special stains which confirmed adenocarcinoma of the lung.

Acknowledgements

None.

Footnote

Conflicts of Interest: The authors have no conflicts of interest to declare.

Informed Consent: Patient has passed away and no next of kin listed. Since there is no identifying information, no individual can object to publication.

References

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