sex cord-gonadal stromal tumor of the rete testis

Sex cord-stromal tumors (SCSTs) represent approximately 3% of testicular neoplasms and are rare outside the testicle.

In the testis, approximately one-half of sex cord-stromal tumors are Leydig cell tumors, with the remainder including Sertoli cell tumors, Granulosa cell tumors, mixed tumors, and tumors of uncertain or indeterminate differentiation (unclassified sex or undifferentiated SCSTs).

Undifferentiated SCSTs are comprised of elements which cannot, at the light microscopic level, be characterized as having Sertoli, Leydig, or Granulosa cell differentiation.

Unclassified SCSTs with a predominance of spindle cells have been described in the testis proper. In these cases, immunohistochemistry is useful to establish that the spindle cell proliferation is of sex cord-stromal origin.

In a series by Renshaw et al., reactivity for S-100 and smooth muscle actin was consistently present. Interestingly, three of the four unclassified SCSTs they identified arose adjacent to the rete testis.

Inhibin is specific for SCSTs and was uniformly reactive in a series of unclassified SCSTs reported by Compérat et al.. In that series, 95% of all SCSTs identified showed immunoreactivity to Vimentin, CD99, and/or inhibin.

The behavior and prognosis of SCSTs is difficult to predict. As many as 80–90% of these lesions behave in a benign fashion, but they cannot be differentiated from germ cell tumors and their behavior cannot be predicted clinically or sonographically.

Features associated with a malignant clinical behavior include large size, invasive margins, vascular invasion, mitotic activity, and necrosis.

References

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 Compérat E, Tissier F, Boyé K, de Pinieux G, Vieillefond A. Non-Leydig sex-cord tumors of the testis. The place of immunohistochemistry in diagnosis and prognosis: a study of twenty cases. Virchows Archiv. 2004;444(6):567–571. [15088145]

 Renshaw AA, Gordon M, Corless CL. Immunohistochemistry of unclassified sex cord-stromal tumors of the testis with a predominance of spindle cells. Modern Pathology. 1997;10(7):693–700. [9237180]