Myoid Gonadal Stromal Tumor

In This Article

Abstract and Introduction

Abstract

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.

Introduction

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.

Table 1. Antibodies Used for Immunohistochemistry Staining
Antibody	Vendor	Pretreatment	Dilution	Incubations (min)^a
Actin, SMA	Dako^b	High pH	RTU	20/15/10
h-Caldesmon	Dako	High pH	RTU	20/20/20/10
Calponin	Dako	Low pH	1:80	20/10/10/10
Calretinin	Dako	High pH	RTU	10/10/10/10
Desmin	Dako	High pH	RTU	20/10/10
FOXL2	Imgenex^c	High pH	1:100	20/10/10/5
Inhibin	Dako	High pH	RTU	10/10/10/10
SF-1	R&D Systems^d	EDTA	1:100	20/10/10/10
SOX9	R&D Systems	Low pH	1:200	20/10/10/10
S100	Dako	High pH	RTU	20/10/10
WT1	Dako	High pH	RTU	20/15/15/10

RTU, ready to use; SMA, smooth muscle actin.
^aPrimary antibody/labeled polymer/DAB development or primary antibody/secondary antibody/labeled polymer/DAB development.
^bCarpinteria, CA.
^cSan Diego, CA.
^dMinneapolis, MN.

Table 2. Pathologic Features of Testicular Myoid Gonadal Stromal Tumor (n = 3)
Case No.	Gross Findings	Growth Pattern	Cell Shape	Nuclear Shape	Nuclear Grooves	Perinuclear Vacuole	Cytoplasm	Atypia	Mitosis per 10 hpf	Necrosis	LVI	IHC Profile
1	Subcapsular, well-circumscribed 1.2-cm golden yellow nodule	Short fascicles	Spindled	Fusiform	Occasional	No	Scant, ill-defined, eosinophilic	No	5	No	No	S100+, SMA+, FOXL2+, SF-1+, vimentin+, inhibin+ (focal weak), desmin–, h-caldesmon–, calretinin–, WT1–, SOX9–, CD34–
2	Well-circumscribed 3.2-cm tan, whorled nodule	Short and broad fascicles	Spindled	Elongated	Occasional	No	Moderate, ill-defined, pale to lightly eosinophilic	Mild	3	No	No	S100+, SMA+, FOXL2+, SF-1+, vimentin+, inhibin+ (focal), calponin+ (focal weak), desmin+ (focal), h-caldesmon–, calretinin–, WT1–, SOX9–
3	Well-circumscribed 1.3-cm yellow-white nodular mass focally contiguous with tunica albuginea	Short fascicles	Spindled	Fusiform	Occasional	No	Scant, ill-defined, pale to lightly eosinophilic	No	<1	No	No	S100+, SMA+, FOXL2+, SF-1+, vimentin+, inhibin+ (focal), calponin+ (focal weak), desmin+, WT1+, h-caldesmon–, calretinin–, SOX9–, CD34–, chromogranin–, synaptophysin–, AE1/3–

hpf, high-power field; IHC, immunohistochemistry; LVI, lymphovascular invasion; –, negative; +, positive.

Table 3. Clinicopathologic Summary of Testicular Myoid Gonadal Stromal Tumors
Reference	No. of Cases	Age, y	Laterality	Size, cm	Follow-up, mo	Disease Status
Evans¹	1	4	Left	3.5	3	Alive and NED
Greco et al²	2	28, 48	Unknown	2, 3.5	12, 32	Both alive and NED
Weidner³	1	46	Right	2.5	12	Alive and NED
Renshaw et al⁵	1 (patient 4)	45	Unknown	2.1	60	Alive and NED
Du et al⁴	1	25	Right	1.5	12	Alive and NED
Kao and Ulbright (present study)	3	38, 43, 59	1 Left, 2 right	1.2, 1.3, 3.2	5, 31, 58	All alive and NED
Total	9	4–59 (mean, 37)	2 Left, 4 right, 3 unknown	1.2–3.5 (mean, 2.3)	3–60 (mean, 25; median, 12)	All alive and NED

NED, no evidence of disease.

Table 4. Immunohistochemical Findings in Myoid Gonadal Stromal Tumor and Potential Mimics ^a
Tumor	S100	SMA	Desmin	h-Caldesmon	Inhibin	Calretinin	SOX9	FOXL2	SF-1
Myoid gonadal stromal tumor	+ (diffuse, strong)	+ (diffuse, strong)	+/–	–	–/+ (focal)	–	–	+	+
Leiomyoma	–	+(diffuse, strong)	+ (diffuse, strong)	+	–	–	–	–	–
Fibrothecoma	Variable	+	+ (focal)	Not available	+	Variable	+/–	+	+

–, negative; +, positive; +/–, positive or negative.
^aReticulin stain works best in differentiating unclassified sex cord–stromal tumor from others, where the former shows reticulin fibers surrounding nested arrangements of cells, but myoid gonadal stromal tumor and fibrothecoma show fibers around individual cells.