Teratoma (Dermoid)

 

Etiology & Epidemiology:

    • Immature teratoma:
      • First three decades most frequently
    • Mediastinum:
      • Mature teratomas:
        • Adolescents most frequently
        • Females always are mature teratomas
      • Immature teratomas:
        • Males only
        • Children and adolescents
      • Malignant teratoma:
        • Males only
    • Klinefelter syndrome:
      • Increased risk of developing germ cell tumours, particularly extragonadal

 

Common sites:

    • Ovary
    • Testis
    • Midline:
      • Anterior mediastinum / thymus
      • Pineal gland
      • Retroperitoneum
      • sacrococcygeal

 

Gross features:

    • Ovary:
      • bilateral 10-15%
      • usually unilocular cyst
      • cyst contains hair and cheesy sebaceous material
      • thin wall lined by opaque, gray-white, wrinkled epidermis, frequently with hair growing from it
      • commonly areas of calcification in wall
      • immature (malignant) teratoma:
        • almost always largely solid
        • areas of necrosis and hemorrhage
        • hair, cartilage, bone, calcification may be present
    • testis:
      • large (5-10cm)
      • heterogenous appearance
      • solid, cartilagenous, cystic areas
      • hemorrhage & necrosis if mixed with embryonal or choriocarcinoma
    • mediastinum:
      • mature teratoma:
        • often cystic
          • brown fluid or oily or grumous materials with or without hair
        • encapsulated
        • variegated cut surface
          • fatty tissue
          • medullary soft tissue
          • flecks of cartilaginous tissue
      • immature teratoma:
        • large (often over 1 kg)
        • solid
        • adhere to or invade adjacent structures and organs

 

Histologic features:

    • heterogeneous collection of differentiated cells and organoid structures, such as:
      • clusters of squamous epithelium
      • brain substance
      • intestinal wall
      • neural tissue
      • muscle bundles
      • islands of cartilage
      • thyroid gland structures
      • bronchial or bronchiolar epithelium
    • embedded in a fibrous or myxoid stroma
    • Rare microscopic foci of immature neural tissue may occur
      • Excellent outcome
    • immature areas:
      • tissues in various stages of maturation from embryonic to fetal
      • organized tissues and stroma composed of small blue cells
      • immature mesenchyme – very cellular, spindle cells
    • immature teratoma (malignant):
      • contains variable amounts of immature (typically primitive/embryonal neuroectodermal) tissues
        • neuroectodermal tubules and rosettes mostly
          • overlapping, hyperchromatic cells lining
          • numerous mitoses
          • pigmented maybe
        • cellular mitotically active glia maybe
        • admixed with ectodermal and endodermal elements with varying degrees of maturation
        • immature cartilage, adipose tissue, bone, and skeletal muscle often
        • embryoid bodies maybe (most primitive component)
          • yolk sac epithelium and germ disc whose epithelium resembles that of embryonal carcinoma
      • Grading:
        • Low-grade (grade 1):
          • Rare foci of immature neuroepithelial tissue
          • < 1 low power field (40X) in any slide
        • High-grade (grade 2/3):
          • Grade 2:
            • 1-3 low power fields (40X) in any slide (immature neuroepithelial tissue)
          • Grade 3:
            • > 3 low power fields (40X) in any slide (immature neuroepithelial tissue)
    • Mediastinum:
      • Mature teratoma:
        • Skin and appendages (constantly)
        • Bronchial tissue
        • Gastrointestinal mucosa
        • Smooth muscle
        • Fat
        • Bone
        • Cartilage
        • Exocrine and endocrine pancreas
          • (not seen in teratomas of the gonads)
        • Salivary gland
        • CNS including ependyma
      • Immature teratoma
        • Occasionally microscopic foci fo nongerm cell malignant tumours
    • Malignant transformation of mature cystic teratoma:
      • germ cell tumour
      • Squamous cell carcinoma
      • Adenocarcinoma
      • Poorly-differentiated carcinoma
      • Adenosquamous carcinoma
      • Sarcoma
        • Embryonal rhabdomyosarcoma
        • Angiosarcoma
        • Myxoid liposarcoma
        • Chondrosarcoma
        • Leiomyosarcoma
        • GBM
        • Neuroblastoma
        • Nephroblastoma
    • Often presence of embryonal, yolk sac, and choriocarcinoma
    • Monodermal teratoma:
      • Struma ovarii:
        • Mature teratoma composed exclusively or predominantly of thyroid tissue
        • Microfollicular architecture maybe
        • Sertoliform tubules maybe
        • Solid areas with abundant eosinophilic or clear cytoplasm maybe
        • Edematous or fibromatous stroma maybe
        • Thyroglobulin and TTF1 positive
        • Benign
        • Carcinoma may arise within similar to thyroid
          • Favourable outcome in general
      • carcinoid
        • grossly uniformly solid, or a nodule/mass within a dermoid cyst or struma ovarii or a mucinous cystic tumour
        • insular carcinoid most common
          • small acini and solid nests
        • trabecular carcinoid is less common
        • strumal carcinoid: associated with struma ovarii (25-45%)
          • intestinal-type mucinous glands component frequently
          • TTF1- / CK7- in carcinoid component
        • Mucinous (goblet cell) carcinoid is rare
        • stroma may be striking and often fibromatous
        • almost invariably benign
          • mucinous carcinoid may have an aggressive behavior particularly if associated with atypical features
      •  

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

 

 

 

 

Molecular features:

    •  

 

Other features:

    • behaviour depends on age in males:
      • benign in children
      • malignant post-puberty
    • mature teratoma
      • benign except if malignant transformation occurs
      • peritoneal implants composed entirely of mature glial tissue may occasionally be observed in cases of mature solid teratoma, but do not adversely affect prognosis
      • rarely immature teratoma develops in residual ovary after excision of a dermoid cyst, particularly if the latter was multiple or had ruptured
    • immature teratoma
      • chemotherapy has improved prognosis
      • stage and grade of the primary tumour and metastases remain important predictive factors
      • prognosis remains favourable even in presence of innumerable military nodules of mature glia in the peritoneum and abdominal lymph nodes

 

References:

    • Kumar V, Fausto N, Abbas A. Robbins & Cotran Pathologic Basis of Disease, Seventh Edition. 7th ed. Saunders; 2004:1552.
    • Shimosato YM, Mukai KM. Tumors of the Mediastinum. American Registry of Pathology; 1998.
    • Kurman RJ, Carcanjiu ML, Herrnington CS, Young RH.  WHO Classification of Tumours of Female Reproductive Organs (2014)
      • (monodermal teratoma and somatic-type tumours and immature teratoma section)