Track: Case Reports

Topic: Neoplasia,Carcinogensis,Tumor Biology

Abstract:

A 64-year-old Vietnamese male presented to the dermatology clinic with a 2-month history of a rapidly growing, ulcerated, firm, red, nodular plaque on the right chin. Prior treatments including incision and drainage and 2 courses of oral antibiotics were ineffective. The patient had no significant past medical history but complained of a chronic cough and was noted to have a 40-pack-year smoking history. A punch biopsy revealed diffuse infiltration of the dermis by atypical epithelioid cells forming glandular structures, consistent with adenocarcinoma. The cells were positive for CK7, CDX2, and CEA, focally positive for CK20 and GATA3, and negative for p63, TTF-1, PAX-8, WT-1 and CD31. A chest CT showed a mass in the right lower lung lobe. Core samples from the pulmonary mass revealed CK7/CK20 positive adenocarcinoma with scattered GATA3, CDX2, and Napsin A positivity. Laboratory evaluation showed elevated CA19-9 (2036 U/mL) and CEA (42.8 ng/mL). A PET-CT revealed FDG avid lesions in the right lung and right chin only. Colonoscopy and MRCP were normal. Taken together, these findings were consistent with metastatic pulmonary enteric adenocarcinoma (PEAC). PEAC represents a rare non-small cell lung cancer subtype which shares morphologic and immunohistochemical features with colorectal adenocarcinoma. Differentiation of PEAC from other forms of non-small cell lung cancer and metastatic colorectal adenocarcinoma is a challenge and relies on clinical, histopathological, immunohistochemical, laboratory and imaging information to confirm the diagnosis. It is important for dermatopathologists to be aware of this rare metastatic process to avoid diagnostic confusion and delays in care.

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Neelesh Jain, MD