Adenomatoid tumor with extensive reactive smooth muscle: a diagnostic dilemma

Abstract

Abstract Introduction/Objective Adenomatoid tumors are slow-growing benign tumors of mesothelial origin. They comprise 30% of all tumors of the paratesticular area. In this location, they commonly involve the epididymis, spermatic cord, ejaculatory duct and rarely testicular parenchyma. Histologically, a spectrum of growth patterns can be seen, such as adenoid, tubular, glandular, solid, or cystic. In some cases, a smooth muscle component can also be present. The purpose of this report is to describe a case of adenomatoid tumor with exuberant smooth muscle component, mimicking leiomyoma. Methods/Case Report A 28-year-old male presented with painless left inguinal bulge. He noticed it five years prior, and it had been slowly growing since then. Examination revealed a paratesticular mass which was subsequently excised. Grossly, the tumor was firm with smooth, white-tan cut surfaces. Microscopically, the tumor was well- circumscribed, showing predominance of smooth muscle bundles and rare cuboidal to ovoid cells in tubular growth pattern. In the background there was little intervening stroma. Immunohistochemical stains showed the cuboidal cells to be positive for WT1 and calretinin, confirming the mesothelial origin. Diagnosis of adenomatoid tumor was rendered. In contrast to adenomatoid tumors, leiomyomas are whiter and firmer on gross examination and lack the characteristic tubules or cystic spaces lined by mesothelial cells. Results (if a Case Study enter NA) N/A Conclusion Exuberant smooth muscle differentiation in adenomatoid tumor can mislead to diagnosis of leiomyoma. Careful inspection for tubules of mesothelial origin and appropriate immunohistochemical stains are key to accurate diagnosis. Pathologists need to be aware of this potential pitfall.