Mature and Immature Teratoma

Synonyms: Differentiated Teratoma

Low-power microscopic view of mature teratoma. Large islands of cartilage are seen surrounding well-differentiated glandular structures.

Definition

Malignant germ cell neoplasm with differentiation towards embryonic structures of endodermal, ectodermal and/or mesodermal derivation. The tissue could either be well differentiated (mature) or primitive (immature).

Clinical Features

5–10% of testicular neoplasms1

Gross Pathology

Predominantly:
- cystic
- multiloculated (Fig. 1
  Fig. 1: Gross appearance of mature (adult) teratoma of testis. There are multiple cystic areas, lobules of mature adipose tissue, and shiny solid nodules corresponding to well-differentiated cartilage.
  )
Usually:
- foci of cartilage
Infrequently:
- bone
Extremely rare:
- sebum, keratin and hairs2 (pilomatrixomas of the testis are probably variations3)

Histopathology

All types of tissue (Fig. 2
Fig. 2: Low-power microscopic view of mature teratoma. Large islands of cartilage are seen surrounding well-differentiated glandular structures.
)
Most commonly:
- neural tissue
- cartilage
- various types of epithelium, which can differentiate in the direction of gastrointestinal, respiratory, cutaneous, or virtually any other tissue type
All cells normally present in the corresponding somatic structures may be identified, including:
- neuroendocrine cells in the case of gastrointestinal epithelium
- meningothelial cells (may form meningioma-like structures) in the case of neural tissue4–6
Sometimes one component (such as cartilage) predominates 7

Diagnosis

Mature teratoma

A requisite for diagnosis is that all tissues are well differentiated

Immature teratoma

WHO classification designation8,9 if there are areas of tissue immaturity in the stroma, epithelium, or neural component; these areas:
- range from a slight hypercellularity of the stroma around the glandular component to large foci of primitive glands, neuroepithelium, or tissue with an appearance reminiscent of Wilms’ tumor (Figs 3 and 4
  Fig. 3: Immature teratoma. Gross appearance.
  Fig. 4: Immature teratoma. Microscopic appearance. Hypercellular stroma is seen growing in a concentric fashion around glandular formations.
  )
- have a yet-to-be-determined prognostic significance
- are not indicative of embryonal carcinoma
- sometimes almost exclusively composed of primitive neuroepithelial tissue with the appearance of neuroblastoma or peripheral neuroectodermal tumor10,11 (primitive neuroectodermal tumor of the testis may represent an extreme manifestation 12)

Immature germ cell tumors with a distinctive appearance

Polyembryomas

Characterized by the presence of multiple embryoid bodies throughout

Diffuse embryoma

Proposed term for a testicular germ cell tumor with an orderly arrangement of embryonal, yolk sac, and trophoblastic elements13,14

Teratoma with malignant transformation (teratoma with malignant areas)

WHO classification designation8,9 for the rare development of a focal malignancy of somatic type in an otherwise mature teratoma;15,16 this is:
- may present as sarcoma (e.g. rhabdomyosarcoma or angiosarcoma)17,18

Prognosis

More important to search for microscopic foci of yolk sac tumor 19 than to determine the extent and grade of the immaturity

Differential Diagnosis

Select up to 2 differential diagnoses to compare with Mature and Immature Teratoma

References

1 Leibovitch I, Foster RS, Ulbright TM, Donohue JP. Adult primary pure teratoma of the testis. The Indiana experience. Cancer. 1995;75:2244–2250.

2 Ulbright TM, Srigley JR. Dermoid cyst of the testis: a study of five postpubertal cases, including a pilomatrixoma-like variant, with evidence supporting its separate classification from mature testicular teratoma. Am J Surg Pathol. 2001;25:788–793.

3 Minkowitz G, Lee M, Minkowitz S. Pilomatricoma of the testicle. An ossifying testicular tumor with hair matrix differentiation. Arch Pathol Lab Med. 1995;119:96–99.

4 Allen EA, Burger PC, Epstein JI. Microcystic meningioma arising in a mixed germ cell tumor of the testis: a case report. Am J Surg Pathol. 1999;23:1131–1135.

5 Michal M. Meningeal nodules in teratoma of the testis. Virchows Arch. 2001;438:198–200.

6 Pichmann S, Mikuz G, Schmid KW. Chromogranins A and B in nonseminomatous testicular tumors. An immunohistochemical study. J Urol Pathol. 1993;1:43–54.

7 Singh N, Cumming J, Theaker JM. Pure cartilaginous teratoma differentiated of the testis. Histopathology. 1997;30:373–374.

8 Bar W, Hedinger CE. Comparison of histologic types of primary testicular germ cell tumors with their metastases. Consequences for the WHO and the British nomenclatures? Virchows Arch [A]. 1976;370:41–54.

9 Mostofi FK, Sesterhenn IA. Histological typing of testis tumours. ed. 2. Berlin: Springer; 1998;.

10 Michael H, Hull MT, Ulbright TM, Foster RS, Miller KD. Primitive neuroectodermal tumors arising in testicular germ cell neoplasms. Am J Surg Pathol. 1997;21:896–904.

11 Serrano-Olmo J, Tang CK, Seidmon EJ, Ellison NE, Elfenbein IB, Ming PM. Neuroblastoma as a prominent component of a mixed germ cell tumor of testis. Cancer. 1993;72:3271–3276.

12 Aguirre P, Scully RE. Primitive neuroectodermal tumor of the testis. Arch Pathol Lab Med. 1983;107:643–645.

13 Cardoso de Almeida PC, Scully RE. Diffuse embryoma of the testis. A distinctive form of mixed germ cell tumor. Am J Surg Pathol. 1983;7:633–642.

14 de Peralta-Venturina MN, Ro JY, Ordóñez NG, Ayala AG. Diffuse embryoma of the testis. An immunohistochemical study of two cases. Am J Clin Pathol. 1994;101:402–405.

15 Ahmed T, Bosl GJ, Hajdu SI. Teratoma with malignant transformation in germ cell tumors in men. Cancer. 1985;56:860–863.

16 Ulbright TM, Goheen MP, Roth LM, Gillespie JJ. The differentiation of carcinomas of teratomatous origin from embryonal carcinoma. A light and electron microscopic study. Cancer. 1986;57:257–263.

17 Hughes DF, Allen DC, O'Neill JJ. Angiosarcoma arising in a testicular teratoma. Histopathology. 1991;18:81–83.

18 Nagahara N, Kitamura H, Kanisawa M, Ikeda A, Shirai K, Matsushita K. A testicular teratoma with rhabdomyosarcoma and seminoma. Acta Pathol Jpn. 1991;41:707–711.

19 Heifetz SA, Cushing B, Giller R, Shuster JJ, Stolar CJ, Vinocur CD, et al. Immature teratomas in children: pathologic consideration: a report from the combined Pediatric Oncology Group/ Children's Cancer Group. Am J Surg Pathol. 1998;22:1115–1124.

Last updated: 30 Mar 2006