Glandular inclusions in inguinal hernia sacs: morphologic and immunohistochemical distinction from epididymis and vas deferens.

Glandular inclusions in inguinal hernia sacs may bear a striking resemblance to the epididymis or vas deferens. Misinterpretation as a transected functional structure may raise significant concerns regarding reproductive capability, even if encountered unilaterally. In a child, resolution of these concerns may be years away with the onset of puberty and documentation of normal sperm counts. CD10 has been shown to be present in Wolffian-type epithelium and to be absent in Mullerian-type epithelium. We hypothesized that an antibody to CD10 would react with vas deferens and epididymis and fail to react with hernia sac inclusions, most of which we thought were Mullerian duct-derived structures. Glandular inclusions in 29 hernia sacs from prepubertal males were classified histologically according to their resemblance to normal structures and analyzed for CD10 by immunohistochemistry. Inclusions resembling vas deferens had their external diameters measured and were also stained for smooth muscle actin. Thirty-one examples of normal vas deferens and 13 examples of normal epididymis were included for comparison. The inclusions were classified as vas deferens-like (9), epididymis-like (13), and Mullerian-like (7). CD10 reactivity was lacking in all vas deferens-like inclusions; their median external diameter was 0.6 mm. Of the epididymis-like inclusions, 7 of 13 were CD10 positive. The CD10-negative cases consisted of glands with well-defined stromal coats distinct from adjacent stromal coats. CD10-positive cases were more numerous, more tightly aggregated, and surrounded by less well-developed stromal coats that blended with adjacent coats. All seven Mullerian-like remnants were CD10 negative. All normal vas deferens and epididymis showed at least focal CD10 reactivity. CD10 positivity in all cases had a luminal membranous staining pattern. Both the vas deferens-like inclusions and the normal vas deferens showed strong smooth muscle actin positivity in their stromal coats. CD10 negativity and external diameter <1 mm are highly useful to distinguish vas deferens-like inclusions from true vas deferens. Epididymis-like inclusions are more problematic. Some react for CD10 and may represent aberrant Wolffian ductules. Others are CD10 negative, distinct from true epididymis, and may be of Mullerian differentiation. Mullerian-like remnants can be diagnosed on the basis of their limited number and scattered distribution. Lack of CD10 immunostaining corroborates this interpretation.