Lymph nodes & spleen, nonlymphoma
Ectopic tissue / inclusions
Other ectopic tissue / inclusions


Topic Completed: 1 June 2006

Minor changes: 6 April 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: Extramedullary hematopoiesis[TI] lymph node, Megakaryocytes [title] lymph nodes, Nevus cells [title], Squamous epithelium inclusions lymph nodes, Thymus [title] lymph nodes [title]


Page views in 2021 to date: 39
Cite this page: DePond W. Other ectopic tissue / inclusions. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lymphnodesotherectopic.html. Accessed April 18th, 2021.
Extramedullary hematopoiesis

Definition / general

Microscopic (histologic) images

Contributed by Nikhil Sangle, M.D.

Liver with extramedullary hematopoiesis



Differential diagnosis
Megakaryocytes

Definition / general
  • Often associated with extramedullary hematopoiesis when present in lymph nodes

Case reports

Microscopic (histologic) images

Images hosted on other servers:
Missing Image

Megakaryocytes in bone marrow



Positive stains

Negative stains

Differential diagnosis
  • Multinucleated histiocytes:
    • Larger, more cytoplasm, vesicular nuclei that are not multilobated
    • CD68+
Nevus cells

Definition / general

Microscopic (histologic) description
  • Single cells, linear arrangements or aggregates of small, round / oval nevus cells with moderate pale / clear cytoplasm, round nuclei with fine chromatin, no prominent nucleoli or pleomorphism, usually within fibrous capsule and trabeculae but also within nodal parenchyma or surrounding a small vessel (Am J Surg Pathol 2003;27:673, Am J Surg Pathol 1996;20:834)

Microscopic (histologic) images

Contributed by Debra L. Zynger, M.D.
Nests within capsule

Nests within capsule

Bland cells

Bland cells

SOX10

SOX10

S100

S100

AE1/3

AE1/3



Positive stains

Negative stains

Differential diagnosis
  • Blue nevus:
    • Also spindled / dendritic cells with heavy pigmentation
  • Metastatic carcinoma or melanoma:
    • Usually not confined to capsule, atypia, mitotic figures, different immunostaining
  • Spitz nevus:
    • Larger cells with abundant eosinophilic cytoplasm
    • Vesicular nuclei with prominent nucleoli
Squamous epithelium

Definition / general
  • Also called lymphoepithelial cyst
  • Most common in upper cervical nodes
  • Depending on location, may be a branchial pouch derivative or derive from metaplastic calyceal urothelium (Hum Pathol 1990;21:1239)

Case reports

Microscopic (histologic) description
  • Small cystic structures lined by well differentiated squamous epithelium

Differential diagnosis
Thymus

Definition / general
  • Ectopic thymus may be present in supraclavicular nodes

Microscopic (histologic) description
  • Lymphoid stroma with Hassall corpuscles

Differential diagnosis
Back to top
Image 01 Image 02