Intratesticular fibroma of gonadal stromal origin, with or without minor sex cord elements, must be considered, analogous to similar tumours in ovary, as a benign tumour.
Histologic and/or immunohistochemical evidence of sex cord differentiation confirms that it could constitute a distinct clinicopathologic entity among unclassified sex cord–stromal tumours. It could be considered the testicular equivalent to ovarian fibroma.
On gross examination, the lesions are circumscribed, firm, whitish, and intratesticular. They usually measure 0.8 and 1.5 cm in diameter. Gross necrosis and hemorrhage are usually absent.
On light microscopy, the tumours consists of a nonencapsulated proliferation of irregularly intermixed fusiform cell bundles separated by a hyalinized fibrocollagenous stroma containing scattered blood vessels. Cellularity may fluctuate in the various sites. The spindle cells are arranged in some areas in a storiform or hemangiopericytoma-like pattern. They have scant, slightly eosinophilic cytoplasm and elongated nuclei with tapered ends. Mitotic figures usually range from 1 to 2 per 10 high-power fields. In some cases after examination of multiple-level sections a minor sex cord component may be found in the periphery of the tumour. It may be composed of small cells with scant basophilic cytoplasm and an elongated hyperchromatic nucleus, as in indifferentiated cells of sex cord type. In adjacent testicular parenchyma, spermatogenesis may be normal or immature in seminiferous tubules.
By immunohistochemistry, spindle cell tumours are positive for vimentin, smooth muscle actin, and sometimes for desmin, cytokeratin, and S100 protein.
Differential diagnosis includes rare cases of intratesticular leiomyoma. Both intratesticular fibroma and leiomyoma of the testis are spindled neoplasms with potential immunoreactivity for vimentin, smooth muscle actin, and desmin. The finding of a minor sex cord component or a positive reaction for MIC2 and inhibin in intratesticular fibroma can be very helpful features in differentiating these 2 entities.
Differential diagnosis also includes intraparenchymatous growth of neurofibroma and solitary fibrous tumor of the tunica vaginalis. Neurofibroma contains spindle cells positive for S100 protein, but negative for smooth muscle actin, desmin, MIC2, and anti-inhibin.
Solitary fibrous tumor of tunica vaginalis contains spindle cells positive for CD34, unlike intratesticular fibroma.
Abstract
Testicular fibroma of gonadal stromal origin with minor sex cord elements: clinicopathologic and immunohistochemical study of 2 cases. Arch Pathol Lab Med.1999 May;123(5):391-4.
OBJECTIVE: To report the histologic and immunohistochemical features of 2 cases of intratesticular fibromatous tumors. RESULTS: Microscopically, these tumors were composed of short, randomly interweaving fascicles of spindle cells dispersed within a fibrocollagenous stroma. A sex cord component was detected in one case by microscopic examination and in both cases by immunohistochemical study using MIC2 and anti-inhibin antibodies. CONCLUSIONS: The presence of minor sex cord elements, morphologically or by immunohistochemistry, suggests that these fibromatous tumors are related to and are a subset of sex cord-stromal tumors. Intratesticular fibromatous tumors, of which 11 other cases lacking sex cord elements have been reported, could be considered as the testicular equivalent of ovarian fibroma. These tumors could then be referred to as testicular fibroma of gonadal stromal origin, with or without minor sex cord component.
Abstract:
Benign fibromatous tumors of the testis and paratesticular region: a report of 9 cases with a proposed classification of fibromatous tumors and tumor-like lesions. Am J Surg Pathol.1997 Mar;21(3):296-305.
Benign intrascrotal fibrous proliferations are uncommon, with most arising from the paratesticular region and falling into the category of so-called fibrous pseudotumor. We describe two neoplastic forms of benign fibrous tumor of the testis and its adnexa: fibroma of gonadal stromal origin and fibroma of the testicular tunics. Three patients with gonadal stromal fibroma were 28, 33, and 35 years of age and presented with painless masses. The tumors were circumscribed, intratesticular, yellow-white or white lesions 0.9 to 4.0 cm in diameter and had microscopic features identical to those of the ovarian fibroma. Immunohistochemically, the tumor cells were strongly positive for vimentin (3/3 cases), focally positive for actin and desmin (2/3 cases) and negative for S-100, keratin, and CD34 (3/3 cases). Six fibromas of the testicular tunics arose in patients 22, 34, 60, 68, 70, and 74 years old and were also asymptomatic masses. Four of them were circumscribed, whorled, white masses arising from the tunica albuginea with variable areas of myxoid change; one was pedunculated and grew exclusively into the cavity of the tunica vaginalis, whereas the other three at least partially extended into the testis as well. The other two tumors were unattached to the tunica albuginea and presented as circumscribed, white-tan paratesticular masses, partially covered by tunica vaginalis. Microscopically, the tumors were slightly to moderately cellular, with bland spindle or stellate cells lying in a myxoid or collagenous stroma with prominent vessels. The two paratesticular tumors had features typical of solitary fibrous tumor. Immunohistochemically, the fibromas of the testicular tunics were negative for S-100, keratin, and desmin. Focal, weak reactivity for actin was present in one case. CD34 was positive in three cases; in the two tumors resembling solitary fibrous tumors it was strong, and in the other it was focal and was limited to the region just below the tunica vaginalis. Eight tumors were treated by radical orchiectomy and one by excision of the mass alone. The outcome was benign in the seven cases in which followup information is available.
Abstract:
Benign fibrous tumor of the tunica vaginalis testis. Report of a case with light, electron microscopic, and immunocytochemical study, and review of the literature.Arch Pathol Lab Med.1992 Mar;116(3):277-80.
Benign fibrous tumor of the tunica vaginalis testis is an uncommon lesion of unknown pathogenesis and histogenesis, frequently described as fibrous pseudotumor. We describe a case of a fibrous tumor of the tunica vaginalis testis studied with light, immunocytochemical, and electron microscopy in a 64-year-old man who also developed a metachronous renal cell carcinoma. To our knowledge, this is the first such case to be presented. We describe the cell of origin of this rare entity and its similarity to fibrous tumors of pleura and extrapleural sites, with a review of the English-language literature and emphasize that not all intrascrotal tumors are malignant.
