TTF-1 Immunoexpression in Primary Rectal Adenocarcinoma with Brain Metastasis

Abstract

Abstract Introduction/Objective Rectal adenocarcinoma metastatic to the brain occurs in 0.6%-3% of cases and is associated with advanced-stage disease.TTF-1 expression in rectal adenocarcinoma is an uncommon finding and less than five cases of TTF-1 positive rectal adenocarcinomas have been reported in the literature. Herein, we report a primary rectal adenocarcinoma with biopsy-proven brain metastasis, radiographic evidence of hepatic and pulmonary involvement and unique expression of TTF-1, a marker with high sensitivity for primary pulmonary and thyroid lesions. Furthermore, we discuss the importance of distinguishing this entity from Pulmonary Enteric Adenocarcinoma (PEA). Methods/Case Report A 68-year-old male with hypertension presented with a two-day history of left facial drooping and dysarthria. Brain MRI revealed a 2.9 cm, contrast-enhancing, solitary, right insular mass. A pterional craniotomy and gross total resection of the lesion was performed. Microscopic examination revealed metastatic adenocarcinoma with immunohistochemical expression of CAM 5.2, CDX2, CK20, focal immunoreactivity with Napsin A and TTF-1, and lack of expression of CK7 and Synaptophysin. Radiographic investigation revealed a right posterior rectal lesion and multiple hepatic and bilateral pulmonary nodules. Sigmoidoscopy a fungating, partially circumferential, ulcerated, and friable rectal mass extending 6 cm proximally from the anal verge. Biopsy demonstrated invasive well- differentiated rectal adenocarcinoma with microsatellite stable phenotype, expression of CDX2, CD20, TTF-1 in the lesional cells, and lack of immunostaining with CK7. Given these findings, we favored a diagnosis of invasive well- differentiated rectal adenocarcinoma. Results (if a Case Study enter NA) N/A Conclusion TTF-1 positive rectal adenocarcinoma is an important differential diagnosis for PEA. As the two primary lesions share histomorphological features, clinical history, radiological findings and immunohistochemical staining with CK7 can aid in distinguishing between the two entities. Recent literature suggests a possible role for CDH17 and SATB2 immunostaining to increase the sensitivity and specificity of distinction between the two entities. Lack of expression of CK7 in both the rectal and brain lesion biopsies, radiological finding of numerous bilateral pulmonary infiltrates and one large, solitary rectal mass supports the diagnosis of advanced stage primary rectal adenocarcinoma with distal metastasis in our patient.