Vulva, vagina & female urethra

Mesenchymal neoplasms

Smooth muscle tumors


Editorial Board Member: Ricardo R. Lastra, M.D.
Deputy Editor-in-Chief: Jennifer A. Bennett, M.D.
David B. Chapel, M.D.

Topic Completed: 27 April 2021

Minor changes: 27 April 2021

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PubMed Search: leiomyoma vulva [title] or leiomyosarcoma vulva [title]

David B. Chapel, M.D.
Page views in 2020: 748
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Cite this page: Chapel DB. Smooth muscle tumors. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/vulvaLMS.html. Accessed October 21st, 2021.
Definition / general
  • Leiomyoma and leiomyosarcoma are, respectively, the most common benign and malignant mesenchymal neoplasms of the vulva and vagina
  • Subset of tumors with equivocal features is diagnosed as smooth muscle tumor of uncertain malignant potential (STUMP)
Essential features
  • Leiomyoma and leiomyosarcoma are, respectively, the most common benign and malignant vulvovaginal mesenchymal tumors
  • The morphologic spectrum of vulvovaginal smooth muscle neoplasia mirrors that seen in the uterus, including leiomyoma variants
  • Although myxoid stroma is more common in vulvovaginal smooth muscle tumors than in their uterine counterparts, conventional spindled morphology still predominates
  • The diagnostic criteria for vulvovaginal leiomyosarcoma have evolved over the last 5 decades, with recent evidence suggesting that criteria for diagnosing malignancy in uterine smooth muscle tumors are also accurate in vulvovaginal tumors
  • The diagnosis smooth muscle tumor of uncertain malignant potential (STUMP) is applied to tumors with worrisome morphologic features that fall short of the diagnostic threshold for leiomyosarcoma
Terminology
  • For uniformity of diagnosis, smooth muscle tumor of uncertain malignant potential should be used, when applicable, in place of atypical leiomyoma or atypical smooth muscle tumor
ICD coding
  • ICD-10: D28.0 - benign neoplasm of vulva
  • ICD-10: C51.9 - malignant neoplasm of vulva, unspecified
  • ICD-10: D28.1 - benign neoplasm of vagina
  • ICD-10: C52 - malignant neoplasm of vagina
Epidemiology
Sites
Clinical features
Diagnosis
Radiology description
Radiology images

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Vulvar leiomyoma

Vaginal leiomyoma, MRI

Vaginal leiomyoma, MRI and angiography


Vaginal leiomyoma, ultrasound

Vaginal leiomyoma, MRI & CT

Vaginal leiomyosarcoma, MRI

Prognostic factors
  • Leiomyoma: excellent prognosis
  • Smooth muscle tumor of uncertain malignant potential (STUMP): intermediate prognosis
  • Leiomyosarcoma: guarded prognosis
    • In a recent study with median follow up of 64 months (Am J Surg Pathol 2018;42:84):
      • Local or distant recurrence in 12 of 15 (80%) vulvovaginal leiomyosarcomas
      • Distant metastasis in 10 of 15
      • Death from disease in 8 of 15
    • Recurrences reported up to 10 years after diagnosis (Am J Surg Pathol 1996;20:779)
Case reports
Treatment
Clinical images

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Vulvar leiomyoma, preoperative examination

Vulvar leiomyoma, intraoperative

Vulvar leiomyosarcoma, preoperative examination

Vaginal leiomyosarcoma, preoperative examination

Gross description
Gross images

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Vulvar leiomyoma, excision specimen

Vulvar leiomyoma, cut surface

Vaginal leiomyoma, cut surface

Vaginal leiomyosarcoma, gross examination

Microscopic (histologic) description
Microscopic (histologic) images

Contributed by David B. Chapel, M.D.
Vulvar leiomyoma Vulvar leiomyoma Vulvar leiomyoma

Vulvar leiomyoma

Vulvar leiomyosarcoma, low grade Vulvar leiomyosarcoma, low grade Vulvar leiomyosarcoma, low grade

Vulvar leiomyosarcoma


Vulvar STUMP

Vulvar STUMP

Vaginal leiomyosarcoma Vaginal leiomyosarcoma Vaginal leiomyosarcoma

Vaginal leiomyosarcoma

Virtual slides

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Vulvar leiomyosarcoma

Negative stains
Electron microscopy description
  • Pleomorphic cells with complex cytoplasmic projections (Taiwan J Obstet Gynecol 2020;59:314)
  • Well developed rough endoplasmic reticulum
  • Large indented nuclei with prominent nucleoli
  • Myofilaments may be rare
  • Intercellular junctions absent
Electron microscopy images

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Scanning and transmission electron micrographs

Sample pathology report
  • Leiomyoma:
    • Right labial mass, excision:
      • Leiomyoma (3 cm) (see comment)
      • Margins negative
      • Comment: Microscopic examination reveals a well circumscribed tumor composed of fascicles of bland spindle cells with abundant eosinophilic cytoplasm. The tumor is entirely submitted for histologic examination. No necrosis or mitoses are identified. The morphology is consistent with a leiomyoma.
  • STUMP:
    • Right labial mass, excision:
      • Smooth muscle tumor of uncertain malignant potential (4 cm) (see comment)
      • Margins negative
      • Comment: Microscopic examination reveals a smooth muscle tumor, comprised of fascicles of spindle cells with moderate to focally marked nuclear atypia. Mitoses number up to 6 per 10 high power fields. There is no necrosis and the tumor is well circumscribed, without infiltration of surrounding vulvar tissues. Margins are negative (tumor approaches to within 0.3 cm of one unoriented inked margin, block A3). The morphologic findings, including nuclear atypia and increased mitoses, are worrisome but do not reach the threshold for diagnosis of leiomyosarcoma. Accordingly, this tumor is best classified as a smooth muscle tumor of uncertain malignant potential (STUMP). Recent reports indicate that vulvovaginal STUMPs have the potential for local recurrence (see reference) but specific prognostic factors are not well defined. Clinical correlation is advised and close clinical follow up is recommended (Hum Pathol 2020;103:83).
  • Leiomyosarcoma:
    • Right labial mass, wide local excision:
      • Leiomyosarcoma (6.5 cm) (see comment)
      • Comment: Microscopic examination reveals a high grade spindle cell neoplasm, composed of fascicles of atypical to focally pleomorphic cells, with conspicuous mitoses (up to 12 per 10 high power fields), including atypical forms. Tumor type coagulative necrosis is identified and there is multifocal tumor infiltration of surrounding vulvar tissues. Margins are negative (tumor approaches to within 0.4 cm of the inked lateral margin). Immunostains for SMA, desmin and caldesmon are positive, whereas CD34, S100 and CK AE1 / AE3 immunostains are negative. The findings are diagnostic of leiomyosarcoma. Correlation with clinical and radiographic findings is advised.
Differential diagnosis
Board review style question #1

A 36 year old woman undergoes excision of a 3 cm, slow growing, painless vulvar mass. The lesion is well circumscribed and microscopic examination reveals no nuclear atypia, necrosis or mitotic activity. A representative photomicrograph is shown above. Immunostains for smooth muscle actin, desmin and caldesmon are positive. Which of the following statements is true regarding the depicted tumor?

  1. Approximately 50% recur after simple local excision
  2. CD34 immunohistochemistry is positive in > 90% of cases
  3. Estrogen and progesterone receptor are expressed in < 10%
  4. Plexiform architecture merits a malignant diagnosis
  5. This is the most common vulvar mesenchymal neoplasm
Board review style answer #1
E. Leiomyoma is the most common mesenchymal neoplasm of the vulva.

Comment Here

Reference: Smooth muscle tumors
Board review style question #2

A 60 year old woman presents with vaginal bleeding and is found to have a 7 cm prolapsing mass. A preoperative MRI shows infiltration of the rectovaginal septum. A core biopsy is obtained, showing atypical spindle cells with brisk mitoses (up to 12 per 10 high power fields) and coagulative necrosis. A representative photomicrograph is shown above. Immunostains for desmin and caldesmon are positive. Which of the following statements is true regarding the depicted tumor?

  1. Local recurrence or distant metastasis occur in > 50%
  2. Most are grossly and microscopically well circumscribed
  3. Most cases show predominantly epithelioid morphology
  4. MyoD1 immunohistochemistry is strongly and diffusely positive
  5. Positive surgical margins are not associated with increased risk of local recurrence
Board review style answer #2
A. Primary vulvovaginal leiomyosarcoma is associated with > 50% risk of local recurrence or distant metastasis.

Comment Here

Reference: Smooth muscle tumors
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