Testicular Mass in an Adult

Specimen Type:

Testis

History:

A 45-year-old man presented with a mass in the undescended testis clinically suspicious for malignant neoplasm. The sectioning of the testis reveals a 1.0x 0.8 x 0.5 cm well-circumscribed tan-yellow firm nodule that abuts the tunica albuginea. Hemorrhage and necrosis are absent.

Pathologic Features:

Sections contain a sharply delineated tumor which is attached to the tunica albuginea (Figure 3.1) and extends into the testicular parenchyma with a pushing border (Figure 3.2). The tumor is non-encapsulated. The tumor comprises cytologically bland spindle cells in parallel or whorling bundles. (Figure 3.3) Moderate amount of intercellular coarse collagen fibers are present (Figures 3.4, 3.5). No cytological atypia is present (Figure 3.6) but rare mitotic figure is noted (Figure 3.7). The tumor contains numerous scattered mast cells (Figure 3.8). The tumor cells are positive for BCL-2 (Figure 3.9), negative for pan-keratin, cytokeratin 7, smooth muscle actin, desmin, CD34, CD117, CD68, S-100, and HMB45.

Differential Diagnosis:

  • Sex cord-stromal tumor, unclassified (Fig 3.10)
  • Solitary fibrous tumor (Fig 3.11, 3.12)
  • Sarcoma
  • Leiomyoma

Sex cord-stromal tumor of unclassified:The tumors in this category frequent lack specific differentiation or contain patterns and cells resembling to varying degrees both testicular and ovarian elements. Clinically, 10% of patients present with gynecomastica. Microscopically, a spectrum of patterns is seen, ranging from predominantly epithelial to predominantly stromal. The better differentiated tumors typically contain solid to hollow tubules or cords composed of cells resembling Sertoli cells, and islands of cells resembling granulosa cells. The less differentiated tumors exhibit varying degrees of nuclear pleomorphism and mitotic activity; diffuse and sarcomatoid patterns are frequent and it may be difficult or impossible to distinguish the epithelial and stromal components on routine staining. Spindle cell predominant cases are often reactive for S-100 and actin, similar to granulosa cell tumors.

Solitary fibrous tumor: Solitary fibrous tumour (SFT), a rare mesenchymal neoplasm usually arising from the pleura, can also occur in the urogenital tract, including spermatic cord, seminal vesicles, urinary bladder, prostate (Fig 11, 12), and kidney. Two paratesticular tumors with features typical of solitary fibrous tumor were reported (reference 1). However, SFT occurring in the testicular parenchyma has not been reported so far. Microscopically, SFT is described as a "patternless" growth pattern, and consists of haphazardly arranged spindle cells admixed with dense collagenous bands. Immunohistochemically, the tumor consistently expresses vimentin, CD34, bcl2 and CD99.

Sarcoma: The diagnosis of a pure sarcoma of any type in the testis should only be made after thorough sampling to exclude an underling tumor from which the sarcoma may have arisen, such as teratoma. Careful gross examination is also required to exclude growth of sarcoma from paratestis into the testis. Tumor invariably displays malignant features such as nuclear pleomorphism and hyperchromasia, brisk mitotic activity or necrosis.

Leiomyoma: Testis leiomyoma is a very rare neoplasm, and only few cases were reported (reference 3). The diagnosis is made using the same criteria as in the ovary and soft tissue.

Diagnosis:

  • Grossly: Attached to the tunica albuginea; well circumscribed, firm, tan-white to yellow.
  • Microscopically:
    • spindle cells growing in a storiform pattern
    • Variable amount of collagen
    • Spindle cells are bland-looking; mitotic figures may be seen (Cellular tumor may have up to 2 mitotic figures per 10 high-power field)
  • Immunohistochemically: Variable results. Most consistently positive markers are vimentin and actin.

Table 1.Diagnostic Features of Fibroma and Unclassified Sex Cord Stromal Tumor

Distinguishing features Fibroma Unclassified Sex Cord Stromal Tumor
Incidence rate Very rare Common
Components    
Epithelial None Invariably present, even mininal in some cases, with cells resembling Sertoli cells or granulosa cells
Stromal
 
Architecture
Collagen
Present, and pure
 
Storiform pattern
Present
Present, of variable amount
 
Haphazard pattern
None
Immunoprofile Vimentin+ Vimentin+
  Keratin- Keratin+ (Sertoli cells), at least focally
  Actin+ Actin + (Granolosa cells)
  S100- S100+ (Granolosa cells)

Comment: Fibromas of the testicular parenchyma are very rare (ref. 1). Based on the histogenesis, they can be further classified into parenchymal fibroma of gonodal stromal origin and fibroma of tunica albuginea (arising from soft tissue fibroblasts). More common, although still rare, are fibroma of the testicular tunics. There are less than 10 documented cases in the literature. The tumor can be located entirely in the testis as seen in this case, pedunculated, or unattached to the tunica albuginea as a circumscribed paratesticular mass. The major differential diagnosis is unclassified sex cord-stromal tumor (Table 1). Cellular fibromas should be distinguished from exceptionally rare fibrosarcoma of the testis using the similar criteria as in the ovary. The tumors are distinguished from leiomyoma (very rare in the testis) based on the hisotological features; actin staining is not reliable in this differential since it is consistently expressed in fibroma.

References:

  1. Jones MA, Young RH, Scully RE. 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.
  2. Sadowski EA, Salomon CG, Wojcik EM, Albala D. Fibroma of the testicular tunics: an unusual extratesticular intrascrotal mass. J Ultrasound Med. 2001 Nov;20(11):1245-8.
  3. Inman RD , Green NJ , Coppinger SW. Re: Monoclonal antibody confirmation of a primary leiomyoma of the testis. J Urol. 2000 Aug;164(2):460-1.