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Lymph nodes & spleen, nonlymphoma

Ectopic tissue / inclusions

Other ectopic tissue / inclusions


Jayalakshmi Balakrishna, M.D.

Last author update: 1 June 2006
Last staff update: 28 March 2024

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

PubMed Search: Lymph node inclusions

Jayalakshmi Balakrishna, M.D.
Page views in 2024 to date: 1,020
Table of Contents
Extramedullary hematopoiesis | Megakaryocytes | Müllerian inclusions | Nevus cells | Salivary gland | Smooth muscle | Squamous epithelium | Thymus
Cite this page: DePond WD, Balakrishna J, Sharabi A. Other ectopic tissue / inclusions. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lymphnodesotherectopic.html. Accessed April 19th, 2024.
Extramedullary hematopoiesis
Definition / general

Case reports
  • 26 year old woman presented with modified Bloom Richardson grade 2 invasive ductal carcinoma and ipsilateral axillary lymph node metastasis at diagnosis; her cancer was hormone receptor positive, HER2 equivocal (2+) on IHC (Case of the month #537)

Microscopic (histologic) images

Contributed by Nikhil Sangle, M.D., Sherif Shabaan, M.D. and Julie M. Jorns, M.D. (Case #537)
 

Liver with extramedullary hematopoiesis

H&E SLN capsule and parenchyma

H&E SLN capsule and parenchyma

H&E Another region of the SLN

H&E Another region of the SLN

Metastatic carcinoma

Metastatic carcinoma

Cytokeratin AE1 / AE3

Cytokeratin AE1 / AE3



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+
Müllerian inclusions
Definition / general
  • Benign glandular inclusions lined by salpingeal or ovarian epithelium with no endometrial stroma or hemosiderophages

Terminology
  • Also called endosalpingiosis

Sites
Pathophysiology
  • Theories include:
    • Passage of epithelial cells through the tubal ostium for implantation in the peritoneum following peeling, followed by transportation by the lymphatic route to reach the pelvic lymph node
    • Metaplastic origin from the peritoneum
    • Foci of endometriosis
    • Vestiges of paramesonephricus ducts
    • Metastases from ovarian serous borderline tumors (Am J Surg Pathol 2000;24:710)

Clinical features
  • Incidental finding / enlarged lymph nodes

Case reports
Treatment
  • Benign process, with no clinical significance

Gross description
  • Enlarged lymph nodes

Microscopic (histologic) description
  • Glandular / cystic inclusions lined by cuboidal / columnar cells with a Müllerian or coelomic appearance commonly found in the capsule
  • Psammoma bodies are common
  • May undergo squamous metaplasia
  • No / rare mitotic figures, no / mild atypia, no desmoplastic stroma, no endometrial stroma

Microscopic (histologic) images

AFIP images
Missing Image

In pelvic lymph node



Positive stains
Differential diagnosis
  • Metastasis from borderline / malignant ovarian tumors or uterine carcinomas

Additional references
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
Salivary gland
Definition / general
  • Benign salivary gland structures in lymph nodes
  • Includes ducts and acini

Terminology
  • Salivary gland inclusions
  • Ectopic salivary tissue
  • Heterotropic salivary gland tissue

Epidemiology
  • Common incidental finding

Sites
  • Most common in upper cervical lymph nodes
  • Rarely - thoracic, mediastinal lymph nodes

Pathophysiology
  • Considered a normal event related to the embryology of the region

Clinical features
  • None - incidental finding
  • Enlarged lymph nodes

Prognostic factors
  • Benign with no significance
  • May undergo diseases of salivary glands including neoplastic processes - Warthin tumor is most common tumor

Case reports
Treatment
  • Usually none but may be indicated based on clinical situation

Clinical images

Images hosted on other servers:

Circumscribed mass lesions due to
sialometaplasia arising in ectopic
salivary gland ductal inclusions



Gross description
  • Normal / enlarged lymph nodes

Microscopic (histologic) description
  • Both ducts and acini are usually present
  • Benign ducts are lined by double layer of epithelium and myoepithelium
  • Benign acini have zymogen granules

Microscopic (histologic) images

AFIP images
Missing Image

Salivary gland inclusion in lymph node



Images hosted on other servers:
 

Inclusions undergoing sialometaplasia show extensive squamous metaplasia

Inclusions with sialometaplasia: SMA



Differential diagnosis
Additional references
Smooth muscle
Definition / general
  • Topic discusses the presence of smooth muscle within the capsule and hilum of normal lymph nodes
  • Common, incidental finding in lymph nodes of hilar smooth muscle proliferation, more commonly in males than females (Virchows Arch A Pathol Anat Histopathol 1985;406:261)

Sites
  • Superficial, inguinal and axillary lymph nodes are most commonly involved

Etiology
  • Suggested etiological factors include back pressure in efferent lymphatics, local inflammation

Clinical features
  • Asymptomatic, with no apparent clinical significance, but may have enlarged lymph nodes

Diagnosis
  • Biopsy
  • Immunohistochemistry for smooth muscle to confirm

Case reports
Gross description
  • Enlarged lymph nodes with firm, tan cut surface

Microscopic (histologic) description
  • Nodal architecture is well preserved
  • Muscle fibers run parallel to capsule or hilar blood vessels
  • Varied patterns of hilar changes:
    • Smooth muscle fibers may be densely interwoven within fibrous tissue and hug the hilar nodal capsule
    • Smooth muscle fibers may form a loose network extending in all directions within hilar adipose tissue
    • Smooth muscle may surround individual islands of fat cells

Microscopic (histologic) images

Images hosted on other servers:
Missing Image

Angiomyomatous hamartoma of lymph node



Positive stains
Negative stains
Differential diagnosis
Additional references
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
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