Soft tissue
Uncertain differentiation

Topic Completed: 1 November 2012

Revised: 5 September 2019

Copyright: 2002-2019,, Inc.

PubMed search: Myospherulosis

Vijay Shankar, M.D.
Page views in 2018: 1,006
Page views in 2019 to date: 750
Cite this page: Shankar V. Myospherulosis. website. Accessed September 22nd, 2019.
Definition / general
  • Iatrogenic benign mass composed of fungi-like spherules that are actually erythrocytes damaged by endogenous and exogenous fat
  • Due to erythrocyte damage from endogenous and exogenous fat
  • Also due to endogenous membranocystic degeneration of fat that occurs in lupus erythematosus and in membranous lipodystrophy with dermal atrophy due to local application of steroid ointment (Arch Dermatol 1991;127:88)
  • In the gluteal region, this entity is described in relation to old injections of petrolatum based hormones and penicillin (Diagn Cytopathol 1988;4:137, J Am Acad Dermatol 1989;21:400)

  • First described by McClatchie (E Afr Med J 1969;46:625), who reported 7 patients from Kenya with unusual soft tissue nodules in arm, legs and subcutaneous tissue of buttock
  • Called myospherulosis due to the involvement of skeletal muscle in some patients (Am J Clin Pathol 1969;51:699)
  • Five patients were subsequently reported by Hutt in Uganda (Trans R Soc Trop Med Hyg 1971;65:182)
  • Initially these structures were thought to be a fungus, but the usual stains for fungi were negative
  • Kyriakos (Am J Clin Pathol 1977;67:118) reported non African cases in paranasal sinuses, nasal cavity and middle ear; most patients had undergone surgery and the surgical wound was packed with gauze impregnated with petrolatum and tetracycline ointment, suggesting an iatrogenic etiology
  • De Schriver and Kyriakos confirmed this etiology by inducing similar lesions in experimental animals (Am J Pathol 1977;87:33)
  • Rosai (Am J Clin Pathol 1978;69:475) and Wheeler (Arch Otolaryngol 1980;106:272) demonstrated that the spherules were erythrocytes damaged by endogenous and exogenous fat
  • Travis (Arch Pathol Lab Med 1986;110:763) and Shimada (Am J Surg Pathol 1988;12:427) confirmed the presence of damaged erythrocytes by immunostaining for hemoglobin
  • Kakizaki (Am J Clin Pathol 1993;99:249) demonstrated that the wall of the spherules was due to the physical emulsion phenomenon that occurs between lipid containing materials and blood
  • The damaged erythrocytes are enclosed by a lipid membrane and later phagocytosed by histiocytes as part of the lipogranulomatous reaction that takes place in adipose tissue
Clinical features
Case reports
Treatment and prognosis:
  • Benign process; no treatment needed other than for symptomatic relief
Gross description
  • Large saccular cyst-like lesion, surrounded by fat
  • May contain oily substance with a yellow color
Gross images
Images hosted on PathOut server:

Buttock tumor

Images hosted on other servers:

Large gluteal mass

Microscopic (histologic) description
  • Cyst composed of spherules which are damaged erythrocytes
  • Wall of the cyst made of fibrous tissue, accompanied by a lipogranulomatous reaction
  • Many eosinophilic spherules containing red blood cells are within histiocytes lining the cyst wall
  • Some larger spherules resemble a bag of marbles
  • Dermal nodules are cystic cavities with a fibrous wall lined by histiocytes and multinucleated foreign body giant cells, with lipogranulomatous inflammation in the adipose tissue adjacent to the cavities
Microscopic (histologic) images
Images hosted on PathOut server:

Case of the Week #173:

Buttock tumor

Images hosted on other servers:

Gluteal mass

Negative stains
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