Lipid Cell Tumor

Definition

Clinical Features

• Any age1
• Most associated with a virilizing syndrome (defeminization and amenorrhea)2
• Sometimes:
  • Cushing's syndrome3
  • clinically biologically inactive
  • estrogenic or progestogenic manifestations
  • associated with endometrioid carcinoma4

Pathogenesis

• Tumors can arise from any of normal steroid hormone-secreting cells, i.e.:
  • lutein (thecal or stromal)
  • Leydig (hilus)
  • adrenal cortical5

Gross Pathology

• Usually unilateral
• Composed of yellow or yellowish brown nodules separated by fibrous trabeculae (Fig. 1
  

  Fig. 1: Cut surface of ovarian lipid cell tumor. The deep brown color is reminiscent of a renal or thyroid oncocytoma.

  )
• Malignant tumors tend to:
  • be larger (≥cm in diameter)
  • have foci of necrosis and hemorrhage

Histopathology

• Masses of large rounded or polyhedral cells Figs 2 and 3
  

  Fig. 2: Lipid cell tumor showing acidophilic appearance of the cytoplasm of the tumor cells.

  

  Fig. 3: Lipid cell tumor showing clear appearance of the cytoplasm of the tumor cells.

  )
• Composed entirely of cells with features indicative of steroid hormone secretion:
  • cytoplasm:
    • abundant
    • eosinophilic
    • may be vacuolated
    • often positive for fat stains
• Malignant tumors tend to exhibit:
  • nuclear atypia
  • mitotic activity1,6
• Ultrastructurally:
  • cytoplasm contains:
    • well-developed smooth endoplasmic reticulum
    • mitochondria with tubulovesicular cristae7

Special Stains and Immunohistochemistry

• Immunohistochemically:
  • reactivity for:
    • vimentin in 75%
    • keratin in 50%
    • actin in ≈33%8
• consistent reactivity for:
  • inhibin
  • A103
  • Mart-1

Diagnosis

• Reinke's crystalloids in a few cases:
  • tumor can then be categorized as Leydig or hilus cell tumor5,10,11
• In few others, ectopic adrenal origin suggested by:
  • hormonal profile (presence of Cushing's syndrome)3
  • adrenal cortical rests in hilus of ovary and broad ligament (but not within adult ovary itself)
• In most cases, exact origin undecided:
  • descriptive term lipid cell tumor proposed for entire group, with added designation Leydig cell type or adrenal cortical type if indicated1,3

Other Investigations

• Variety of androgenic hormones produced in vitro:9
  • occasionally, large amounts of adrenal corticoids

Differential Diagnosis

• Distinguish from lesions in which steroid hormone-producing cell proliferation is secondary event, including:
  • stromal luteoma
  • luteinized granulosa cell tumor (particularly juvenile type)
  • fibrothecoma
  • stromal–Leydig cell tumor
  • non-neoplastic proliferation of steroid cells at periphery of other tumors, such as:
    • struma ovarii
    • strumal carcinoid
    • surface epithelial tumors
    • metastatic carcinoma12

Prognosis

• If Reinke's crystalloids almost invariably benign1,10
• Incidence of clinical malignancy ≈25%:1,6
  • malignant tumors can lead to peritoneal implants1