Lymph nodes - not lymphoma
Inclusions, pigment, ectopic cells or tissue
Smooth muscle

Senior Author: Abdelsalam Sharabi, M.D.
Jayalakshmi Balakrishna, M.D.

Topic Completed: 1 September 2014

Revised: 2 February 2019, last major update September 2014

Copyright: (c) 2003-2018,, Inc.

PubMed Search: Smooth muscle [title] lymph nodes

Jayalakshmi Balakrishna, M.D.
Page views in 2018: 400
Page views in 2019 to date: 331
Cite this page: Balakrishna J. Smooth muscle. website. Accessed October 21st, 2019.
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)
  • Superficial, inguinal and axillary lymph nodes are most commonly involved
  • 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
  • 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

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Angiomyomatous hamartoma of lymph node

Negative stains
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