PMC4978837_01
(a) Ultrasound imaging demonstrating hypoechoic mass at left penoscrotal junction. (b) Subcutaneous, unencapsulated, but well-circumscribed scrotal lesion with unremarkable overlying epidermis (H&E x5). (c) Interlacing fascicles and bundles of smooth muscle with eosinophilic cytoplasm and elongate, cigar-shaped nuclei (H&E x100). (d) Rare mitotic figure (H&E x400).
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This demonstrated a 7 mm superficial, hypoechoic soft-tissue nodule (Figure 1(a)). Histologic evaluation revealed a well-circumscribed, nodular lesion arising from the tunica dartos, comprised of interlacing fascicles of bland, spindled cells with eosinophilic cytoplasm and blunt-ended, elongated, cigar-shaped nuclei with perinuclear halos and mild to moderate cytologic atypia (Figures 1(b) and 1(c)). Rare mitotic figures without atypia (0-1 per 10 high-power fields) were present (Figure 1(d)), without myxoid change or hyalinization.
(a) Immunohistochemical staining for desmin shows strong, diffuse cytoplasmic staining of the lesional cells (x100). (b) Immunohistochemical staining for Ki-67 shows positivity in 1-2% of lesional nuclei (x400). (c) Immunohistochemical staining for fumarate hydratase, demonstrating intact expression of this enzyme in lesional cells (x200).
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Immunohistochemical staining demonstrated immunoreactivity of the spindled cells using antibodies directed against smooth muscle actin and desmin, but not CD34, S-100 protein, or AE1/AE3, supporting a diagnosis of a smooth muscle neoplasm (Figure 2(a)). The proliferative index of the lesion, as demonstrated by a Ki-67 immunohistochemical stain, was 1-2% (Figure 2(b)). Biotechnology, Santa Cruz, CA) and performed staining on the lesion using two benign uterine leiomyomas as positive controls. By this method, we found intact FH expression in the patient's lesion (Figure 2(c)) suggesting that the tumor most likely arose in a sporadic fashion and offering no overt evidence of FH deficiency or the HLRCC syndrome in the patient, although it should be remembered that FH immunohistochemistry is only 83% sensitive and 75% specific for HLRCC, and intact FH expression does not entirely exclude the possibility of HLRCC.