Ultrasound Examination of Unilateral Seminoma in a Salernitano Stallion

Abstract

An 18-year-old Salernitano stallion developed a progressive enlargement of the left testicle over eight months. An ultrasound evaluation was performed, along with a hormonal profile. A histopathological evaluation of the testis was performed after unilateral orchiectomy. On B-mode ultrasound examination, testicular parenchyma was characterized by the loss of internal structure, with the presence of multiple coalescing, nodular, well-defined and heterogeneous lesions with capsule deformity, appearing with an irregular profile. On dissection, the testicular parenchyma bulged over the cut section, confirming the increase in size. Microscopically, the lesion consisted mainly of large, densely packed, polygonal-to-round-shaped neoplastic cells. Mitotic figures were plentiful and frequently atypical; further microscopic features included apoptosis and necrosis. At immunohistochemistry, the entire neoplasm showed strong and diffuse immunolabeling for vimentin, while CD117-specific immunoreactivity was only observed in scattered clusters of neoplastic cells. Based on the gross, microscopic and IHC findings, a diagnosis of diffuse seminoma was made. Three months later, a follow-up examination showed no evidence of recurrence and the preservation of reproductive abilities. The case presented shows an unusual ultrasonographic pattern for seminoma and the basis of the correlation between the characteristics of the sonoelastographic examination and histological diagnosis.

Keywords: histopathology; seminoma; stallion; testis; ultrasound.

Figure 1

Medio-lateral (A) and caudo-cranial (B) view of the scrotum, showing an increase in the volume of the pathological testis (left) compared to the contralateral (right).

Figure 2

B-mode longitudinal (A) and transverse (B) images of the right testicle; note the homogeneous appearance of normal testicular parenchyma.

Figure 3

B-mode longitudinal (A) and transverse (B) images of the left testicle; the black arrows point at the heterogeneous and well-defined nodular lesions effacing the normal testicular parenchyma.

Figure 4

B-blow images (A,B) and Color Doppler (C,D) of the left testicle; note the heterogeneous vascular lesion distribution appearing as both peripheral and central in different portions of the same testicle.

Figure 5

Images from SE of a normal (A,B) and a diseased testicle (C,D). In panel A and B, the B-mode image and the elastogram are presented, respectively; in the elastogram, notice the color distribution, characterized by central parenchymal red-green color with blue edges (white solid arrow). In panels C and D, B-mode image and elastogram are presented as well, with the elastogram characterized by an heterogenous pattern, mostly blue with a central small green areas (score 5—white solid arrow). The white dotted arrows point at a color bar is indicative of the quality of examination, which is considered good if it appears green.

Figure 6

Images from 2D-SWE of a normal (A,B) and a diseased testicle (C,D). In panels A and B, the B-mode image and the elastogram are presented, respectively; the white dotted arrow points at the values from the ROIS manually drawn on the elastogram (white solid arrow). In panels C and D, a B-mode image and elastogram are presented as well; notice the higher values (white dotted arrow) from the ROIS pointed on the elastogram (white solid arrow).

Figure 7

Horse testis. At the external inspection (a), the shape of the testicle is partially altered, due to the presence of a large bulge (white arrowheads). On the cut section (b), the features of the testicular parenchyma are completely modified. About 50% of the surface appears to be invaded by a cluster of whitish, lardaceous nodules (lower part of the picture), while the remaining part was reddish-to-greyish, with hemorrhagic foci also being evident (bounded with a white line).

Figure 8

Horse testis. (a) Neoplastic cells are densely packed, and multinucleated cells can be easily detected (white arrowheads). Individual cell death (black arrowheads) determines a starry-sky pattern. (b) At a higher magnification, the main features of the neoplastic cells are better appreciated. Most of them are mononuclear and polygonal in shape, with a central, often vesicular nucleus, surrounded by a more or less abundant eosinophilic cytoplasm. Prominent nucleoli are also evident. Multinucleated cells usually have their nuclei arranged in a horseshoe-shaped pattern, at the cell periphery. The apoptosis of a single cell (black arrowhead) and an atypical mitosis (yellow arrowhead) are also seen. (c) Neoplastic cells are arranged as cords, tubular-like structures (red asterisks) embedded within nucleoli are very evident, and the stroma shows a loose appearance. (d) A lymphocytic aggregate is shown embedded within the neoplastic proliferation. Hematoxylin and eosin stain. Final magnification: ×200 (a,c,d), ×400 (b).