Myoid Gonadal Stromal Tumor

A Clinicopathologic Study of Three Cases of a Distinctive Testicular Tumor

Chia-Sui Kao, MD; Thomas M. Ulbright, MD


Am J Clin Pathol. 2014;142(5):675-682. 

In This Article

Abstract and Introduction


Objectives To report three new cases of testicular myoid gonadal stromal tumor to better characterize its features.

Methods The clinicopathologic findings (including follow-up) were evaluated and a review of the literature was performed.

Results The patients were 38, 43, and 59 years old, and tumor sizes were 1.2, 1.3, and 3.2 cm. All were unilateral, well circumscribed, adjacent to the rete testis, and composed exclusively of spindled cells with elongated nuclei and occasional nuclear grooves arranged in fascicles with admixed variably ectatic blood vessels. Nucleoli were inconspicuous, and the cytoplasm was scant, ill-defined, and pale/lightly eosinophilic. No sex cord component was present. Mitotic figures ranged from zero to five per 10 high-power fields. Significant atypia, lymphovascular invasion, and necrosis were absent. All were consistently positive for smooth muscle actin, S100 protein, FOXL2, and steroidogenic factor 1 but negative for h-caldesmon, calretinin, and SOX9. Inhibin and calponin were focally positive. All patients were alive and well at 5, 31, and 58 months postorchiectomy. Combining our cases with those previously reported (n = 6) shows that this neoplasm occurs mostly in younger men (mean, 37 years), and all follow-up thus far (mean, 25 months) has been benign.

Conclusions Myoid gonadal stromal tumors are small (<4 cm) indolent testicular tumors distinctly different from other sex cord–stromal tumors and are adequately managed by orchiectomy.


Myoid gonadal stromal tumor of the testis is an uncommon spindle cell tumor hypothesized to arise from peritubular myoid cells or intertubular primitive mesenchymal cells.[1–4] To our knowledge, there are only six previously documented cases in the literature, including those reported by Weidner[3] and Du et al,[4] who together defined this rare, yet distinctive, testicular tumor.[1–5] It is characterized by uniform, cytologically bland spindled cells forming short, interwoven fascicles with intervening collagen and coexpression of S100 protein and smooth muscle actin (SMA). All have been small, circumscribed, nonencapsulated masses with no reports of metastasis. In this study, we examined three previously unreported myoid gonadal stromal tumors of the testis to better characterize their clinicopathologic features, including their immunoreactivities for a comprehensive panel of sex cord–stromal markers.[5–15] We also provide additional follow-up concerning this rare entity as well as a review of the literature.