Soft tissue
Fibroblastic / myofibroblastic tumors
Intranodal palisaded myofibroblastoma

Author: Lauren N. Stuart M.D., M.B.A. (see Authors page)
Editor: Jerad M. Gardner, M.D.

Revised: 24 August 2016, last major update April 2013

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Intranodal palisaded myofibroblastoma

Cite this page: Intranodal palisaded myofibroblastoma . PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/softtissueintranodalpalisaded.html. Accessed December 3rd, 2016.
Definition / General
  • Benign lymph node tumor composed of myoid or myofibroblastic spindle cells, with focal palisading and so-called "amianthoid" fibers
  • Distinctly resembles schwannoma
Terminology
  • Also called intranodal hemorrhagic spindle cell tumor with amianthoid fibers
  • Formerly called intranodal schwannoma
  • Amianthoid: resembles amianthus, a type of asbestos with particularly fine fibers (see images below); although tumor fibers resemble amianthoid fibers, they are actually composed of normal thickness collagen rather than the thick collagen fibers comprising "true" amianthoid fibers (Arch Pathol Lab Med 2007;131:306)
  • Initially described by Weiss et al (Am J Surg Pathol 1989;13:341) and Suster et al (Am J Surg Pathol 1989;13:347)

Images hosted on other servers:

Amianthoid

Epidemiology
Sites
Pathophysiology
Clinical Features
Prognostic Factors
Case Reports
Treatment
  • Local excision is almost always curative
Gross Description
  • Well circumscribed, gray-white with hemorrhage and peripheral nodal tissue
Gross Images

Images hosted on other servers:

Lymph node with areas of hemorrhage

Micro Description
5 key features:
  • Spindle cell proliferation surrounded by hemorrhage and collagenous pseudocapsule; growing nodule compresses remaining nodal tissue
  • Bland spindle cells with areas of nuclear palisading
  • Intraparenchymal hemorrhage and red blood cell extravasation
  • So-called amianthoid fibers
  • Extra- and intracellular fuchsinophilic bodies (best seen with SMA stain, Arch Pathol Lab Med 2007;131:306)
Micro Images

Images hosted on other servers:

Figure 1: Amianthoid fibers composed of a central vessel surrounded by a core
of collagen with peripheral spokes, strongly stained by Van Gieson (elastin)



Various images

Cytology Description
  • Moderately cellular with benign appearing, dissociated, single spindle cells with elongated nuclei, pointed ends and occasional twisted forms
  • In pale fibrillary matrix with hemosiderin granules, no atypia (Acta Cytol 2002;46:1143)
Positive Stains
Negative Stains
Electron Microscopy Description
  • Rough endoplasmic reticulum cisternae
  • Some smooth-muscle type myofilaments
  • Subplasmalemmal densities, plasmalemmal caveolae, and external lamina at cell surface
  • Lacks the fibronexus junctions typical of myofibroblasts
  • So-called "amianthoid fibers" are actually collagen fibrils with typical diameter of 50 - 83 nm, compared to giant collagen fibrils typical of true amianthoid (Ultrastruct Pathol 1996;20:79)
Differential Diagnosis
  • Benign metastasizing leiomyoma: smooth muscle cells are more ovoid with more prominent eosinophilic cytoplasm, no hemorrhage, no amianthoid fibers, usually metastasizes to lung
  • Follicular dendritic cell sarcoma: nests or whorls of plump cells with scattered inflammatory cells, no prominent hemorrhage, no amianthoid fibers, CD21+, CD35+
  • Kaposi sarcoma: curved fascicles of spindle cells with atypia and PAS+ hyaline globules, brisk mitotic activity, slit-like vessels with extravasated red blood cells, scattered plasma cells in infiltrate, no amianthoid fibers; HHV8+, FLI1+, CD34+, CD31+
  • Sarcoma (metastatic to lymph node): more atypical and more mitotically active, most sarcomas do not present initially with lymph node metastases (although nodal metastasis may develop in patients with disseminated disease)
  • Schwannoma: often biphasic, no amianthoid fibers, not nodal, S100+
  • Spindle cell carcinoma (metastatic to lymph node): more atypical and more mitotically active, often keratin+, p63+
  • Spindle cell melanoma (metastatic to lymph node): more atypical and more mitotically active, S100+