Other surface epithelial tumors

Undifferentiated carcinoma

Topic Completed: 1 July 2014

Minor changes: 28 June 2021

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PubMed Search: Undifferentiated carcinoma [title] ovary

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Cite this page: Gupta N. Undifferentiated carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/ovarytumorundifferentiated.html. Accessed September 19th, 2021.
Definition / general
  • Undifferentiated carcinomas are characterized by a patternless solid, sheet-like growth of tumor cells, with an aggressive clinical course (Mod Pathol 2010;23:781)
  • There are no nests, papillae, glands, trabeculae or spindled patterns, no squamous or mucinous metaplasia, and no/minimal neuroendocrine differentiation
  • If areas of a differentiated component are found, the tumor is called dedifferentiated carcinoma (Int J Gynecol Pathol 2006;25:52)
Clinical features
  • Abdominal pain or swelling
Radiology description
  • USG: solid adnexal mass with variable hemorrhage and necrosis
Prognostic factors
  • Poor prognosis
  • Presence of undifferentiated component in a differentiated tumor carries similar prognosis as pure undifferentiated carcinoma
  • 83% cases present in FIGO stage III - IV (Mod Pathol 2010;23:781)
Case reports
  • Primary ovarian tumor treated primarily with chemotherapy followed by surgery
  • Total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAH-BSO) with or without lymphadenectomy
Gross description
  • Large tan-brown, fleshy adnexal masses with areas of necrosis, mostly with ovarian surface involvement
Gross images

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Surgical specimen

Microscopic (histologic) description
  • Sheets of dyshesive round to ovoid cells, frequently resembling large cell lymphoma, separated by delicate fibrovascular septa
  • No evidence of gland formation, trabecular or nested growth pattern
  • May have foci of spindling / keratinization / necrosis
  • Vascular invasion in 20%
  • Frequent mitoses and apoptosis; mitotic rate of 5 - 50 per 10 high power fields
Microscopic (histologic) images

AFIP images
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Cells growing in masses

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Atypical nuclei

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Malignant neoplasm of small round cells

Positive stains
  • Focal but strong positivity for AE1 / AE3, EMA, CK18, ER, PR
  • Variable staining for S100, chromogranin, synaptophysin (Mod Pathol 2010;23:781)
Negative stains
  • HMB45
Electron microscopy images

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Undifferentiated neoplasm of polygonal cells

Molecular / cytogenetics description
  • May have loss of MMR proteins, most frequently MLH1 and PMS2, but sometimes MSH2 / MSH6
  • May be associated with hereditary nonpolyposis colorectal cancer / Lynch syndrome
Differential diagnosis
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