Other benign tumors

Benign stromal spindle cell tumors

Last author update: 1 September 2015
Last staff update: 17 February 2021

Copyright: 2002-2019,, Inc.

PubMed Search: Benign stromal spindle cell tumors breast

Monika Roychowdhury, M.D.
Page views in 2021: 4,828
Page views in 2022 to date: 2,996
Cite this page: Roychowdhury M. Benign stromal spindle cell tumors. website. Accessed August 17th, 2022.
Definition / general
  • Represent variations of the same tumor entity, likely arising from the uncommitted vimentin+ / CD34+ fibroblasts of the mammary stroma, capable of multidirectional mesenchymal differentiation (Pathol Res Pract 2001;197:453)
  • Can be subtyped into 4 main groups based on morphology and immunohistochemistry:
  • Mesenchymal tumors composed of cells capable of various lines of differentiation, including fibroblasts, myofibroblasts, adipocytes and smooth muscle cells
  • Histologic variations reflect the features seen in the four types of myofibroblasts:
Clinical features
  • Benign
Case reports
Gross description
  • Solid, well circumscribed, noncystic breast mass
Microscopic (histologic) description
  • Myofibroblastoma:
    • Spindle cells, hyalinized collagen bundles and adipocytes
    • Can have cellular pleomorphism
    • Based on the ratio of components and pleomorphism, subclassified as classic, collagenized, epithelioid, cellular, lipomatous and variants resembling solitary fibrous tumor
  • Spindle cell lipoma: spindle cells intermingled with adipocytes and collagen bundles
  • Hemangiopericytoma:
    • Closely packed, spindle shaped cells with indistinct cell margins arranged around thin walled irregular branching vessels
    • The latter may have a 'staghorn' configuration
Microscopic (histologic) images

Images hosted on other servers:
Missing Image

Spindle cell carcinoma, CD10, S100, SMA

Missing Image

Myofibroblastoma, CD34, S100

Missing Image

Spindle cell lipoma, CD34

Missing Image

Leiomyosarcoma, desmin

Missing Image

Myoepithelial carcinoma, S100, CD10

Cytology description
  • Myofibroblastoma: cellular specimen with bipolar spindle cells, bland nuclei with grooves
  • Nonspecific cytologic features for spindle cell lipoma and hemangiopericytoma
Positive stains
Differential diagnosis
  • Myoepithelial carcinoma, spindle cell subtype: nuclear atypia, mitotic figures, necrosis, keratin+
  • Myofibrosarcoma: mitotic figures and necrosis
  • Nodular fasciitis: spindle to round plump cells with frequent mitoses, myxoid tissue-culture like stroma, inflammatory lymphocytic component and extravasated RBCs
    • Desmin negative, positive for actin and focal CD34
  • Sarcomatoid carcinoma: may have hemangiopericytoma-like vascular pattern but also nuclear atypia, frequent and atypical mitotic figures, necrosis
  • Spindle cell myoepithelioma: no collagen bundles, keratin+
Back to top
Image 01 Image 02