Mediastinum

Thymic carcinoma

Thymic carcinoma-other variants



Last author update: 1 December 2012
Last staff update: 17 April 2024

Copyright: 2003-2024, PathologyOutlines.com, Inc.

PubMed Search: Thymic carcinoma other variants


Hanni Gulwani, M.B.B.S.
Page views in 2023: 2,963
Page views in 2024 to date: 7,574
Cite this page: Gulwani H. Thymic carcinoma-other variants. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/mediastinumthymiccarcinomaother.html. Accessed July 13th, 2024.
Adenocarcinoma
Definition / general
  • Rare, < 10 cases reported
  • Most common type is papillary, mucinous subtype also reported

Epidemiology
  • Mean age 50 years but wide range

Clinical features
  • Must rule out metastatic tumor
  • More likely to be thymic primary if CD5+ and transition from thymoma or thymic cyst to adenocarcinoma is present
  • Outcome is highly variable

Case reports
Basaloid
Definition / general
  • Primary thymic tumor or metastatic tumor to mediastinum from oropharynx, hypopharynx, larynx, esophagus, lung, anorectum

Clinical features
  • Present with intrathoracic mass
  • Primary tumors are associated with multilocular thymic cysts
  • Capable of aggressive behavior and significant mortality (Am J Surg Pathol 2009;33:1113)

Prognostic factors
  • Good prognosis with few fatalities if well differentiated

Microscopic (histologic) description
  • Nests, cords and sheets of small polygonal cells with minimal cytoplasm, hyperchromatic round nuclei, abundant mitotic figures
  • No nuclear molding
  • Separated by myxoid or eosinophilic stroma
  • May have peripheral pallisading of nuclei
  • May have areas of squamous differentiation with keratin pearls or stromal mucin containing gland-like profiles
  • May have cystic structures

Microscopic (histologic) images

Images hosted on other servers:

Prominent peripheral palisading



Positive stains

Negative stains
  • Neuroendocrine markers

Electron microscopy description
  • Poorly differentiated squamous proliferation with limited cytoplasmic tonofilaments, well formed desmosomes, redundant basal lamina
  • No neurosecretory granules
Clear cell
Definition / general
  • Rare; clear cytoplasm due to either glycogen or degenerative changes
  • Almost always fatal

Case reports

Microscopic (histologic) description
  • Lobular or occasionally sheet-like growth pattern of polygonal cells with clear cytoplasm, rather bland nuclear features, round vesicular nuclei, prominent nucleoli; delicate fibrovascular stroma (Am J Surg Pathol 1995;19:835)
  • No blood lakes, no mucin

Microscopic (histologic) images

Images hosted on other servers:

Large cells with abundant optically clear cytoplasm



Positive stains

Differential diagnosis
Mucoepidermoid
Clinical features

Case reports

Microscopic (histologic) description
  • Sheets, lobules and nests of squamous, mucinous and intermediate cells in densely fibrotic stroma

Microscopic (histologic) images

Images hosted on other servers:

Well differentiated mucoepidermoid carcinoma of the thymus

Poorly differentiated
mucoepidermoid
carcinoma of the
thymus

Sarcomatoid
Definition / general
  • Very rare; usually presents as rapidly growing, anterior mediastinal mass
  • Must exclude metastases before making this diagnosis
  • May arise from malignant transformation of preexisting spindle cell thymoma (Am J Surg Pathol 1999;23:691)
  • Aggressive: recurrence, metastasis and death are common

Terminology
  • Also called spindle cell thymic carcinoma

Case reports

Gross description
  • Large (mean 15 cm), well circumscribed, locally infiltrative
  • Firm cut surface, focal hemorrhage, necrosis, cystic changes

Microscopic (histologic) description
  • Irregular fascicles of fusiform and pleomorphic cells with amphophilic or eosinophilic cytoplasm, hyperchromatic nuclei, prominent nucleoli (at least focally), brisk mitotic activity, often atypical mitotic figures
  • May have epithelioid foci
  • Usually transitional areas with spindle cell thymoma
  • May also have lymphoepithelioma-like or anaplastic areas
  • Rarely rhabdomyogenic foci with cross striations

Microscopic (histologic) images

Images hosted on other servers:

Atypical population
of spindle cells
with frequent
mitotic figures



Positive stains

Negative stains

Electron microscopy description
  • Focal junctional complexes between spindle cells, tonofibrils

Differential diagnosis
Undifferentiated
Definition / general
  • Undifferentiated large cell thymic carcinoma accompanied by inflammatory reaction resembling hyaline vascular Castleman disease (Am J Surg Pathol 2005;29:490)
  • May be asymptomatic with incidental detection
  • Tumor cells are cytokeratin+ / CD5-
  • May have neuroendocrine features
  • Indolent behavior
Back to top
Image 01 Image 02