Discussion:

Müllerian adenosarcoma is a biphasic malignant tumor composed of benign müllerian glands and malignant stroma.

It is rare and accounts for 5-7% of uterine sarcomas with a wide age range of 10-90 years (mean: 58 years)

It can presents as abnormal vaginal bleeding, pelvic pain, enlarged uterus, recurrent endometrial polyps and symptoms related to prolapse.

Poor prognosis in high grade sarcomatous growth, myometrial invasion or high grade tumor.

Gross and microscopic description:

Typically polypoid endometrial mass, and rarely mural or serosal.

Cut surface is tan-gray with small cysts and focal hemorrhage and necrosis.

Mixed tumor with benign epithelial and malignant mesenchymal components.

The glands are usually large, dilated, with periglandular stromal “cuffing”. Polypoid projection of stroma into the glandular lumen is characteristic.

Microscopic description:

Hypercellular and atypical stroma with mitosis ranging from 5-20 mitotic figures/10 hpf. There may be extensive stromal fibrosis, hyalinization, elastosis, edema, myxoid change and foamy histiocytes.

Sex cord-like, smooth muscle, osseous, rhabdomyoblastic, cartilaginous and adipocytic differentiation may occur. This case has focus of chondrosarcoma.

When >25% of the tumor is composed of only neoplastic stroma, typically high grade, and often with rhabdomyoblastic differentiation; it is called müllerian adenosarcoma with sarcomatous overgrowth (MASO).

Immunohistochemistry:
  • Stromal component
    • ER, PR and frequently AR positive
    • WT1 and CD10 positive
    • SMA, desmin and CD34 positive
    • ER, PR and CD10 expression very low if sarcomatous overgrowth
    • C-kit negative
  • Epithelial component
    • AE 1/3, ER and PR typically positive
    • CD10 and AR uncommonly positive
Differential diagnosis (1/3):
  • Malignant mixed müllerian tumor
    • BOTH epithelial and stromal components are malignant and high grade
    • Some areas may resemble adenosarcoma architecturally, but cytology is always high grade
    • Extensive areas of necrosis and hemorrhage
  • Embryonal rhabdomyosarcoma
    • Often younger age
    • Rare in uterine corpus (most common in vagina and cervix)
    • Prominent cambium layer
    • Primitive appearing neoplastic mesenchymal cells
    • Minimal glandular component
Differential diagnosis (2/3):
  • Müllerian adenomyoma
    • Most commonly in myometrium
    • Very rarely polypoid and intraluminal
    • Benign endometrioid-type glands and smooth muscle
    • Variable amount of endometrial stroma around glands without “cuffing” or cytologic atypia
  • Müllerian adenofibroma
    • Extremely rare
    • No periglandular “cuffing”
    • Diffusely hypocellular stroma
    • No cytologic atypia
    • Not mitotically active (<2 mitoses per 10 HPF)
Differential diagnosis (3/3):
  • Endometrial stromal sarcoma with glands
    • No phyllodes architecture
    • Permeative infiltrative growth into myometrium
    • The sarcoma is typically low grade
    • Typically only endometrioid-type glands but not tubal, mucinous or squamous epithelium
References:

Nucci, Marisa R., et al. (2014). Diagnostic pathology: gynecological. Amirsys.

Logani, S., MD. Adenosarcoma. (Retrieved 12/20/2017) from http://www.pathologyoutlines.com/topic/uterusadenosarcoma.html

Gattuso, P. (2010). Differential diagnosis in surgical pathology. Philadelphia, PA: Saunders

Kurman RJ., et al. (2014) WHO Classification of tumors of female reproductive organs.

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