Smooth muscle tumor of uncertain malignant potential, abbreviated STUMP, is an uncommon tumor of the uterine

smooth muscle Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...

that may behave like a benign tumor or a cancerous tumor. This tumor should not be confused with the prostatic stromal tumor of uncertain malignant potential which may be abbreviated the same way (''STUMP''). The Bell criteria were developed to help categorize them and differentiate them from their main

differential diagnoses In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...

leiomyosarcoma Leiomyosarcoma is a malignant (cancerous) smooth muscle tumor. A benign tumor originating from the same tissue is termed leiomyoma. While leiomyosarcomas are not thought to arise from leiomyomas, some leiomyoma variants' classification is evolvi ...

and

uterine leiomyoma Uterine fibroids, also known as uterine leiomyomas or fibroids, are benign smooth muscle tumors of the uterus. Most women with fibroids have no symptoms while others may have painful or heavy periods. If large enough, they may push on the bl ...

Bell criteria

Atypia

*none *minimal: smooth nuclei, smooth contours, minimal variation in nuclear size, shape, and evenly distributed

chromatin Chromatin is a complex of DNA and protein found in eukaryotic cells. The primary function is to package long DNA molecules into more compact, denser structures. This prevents the strands from becoming tangled and also plays important roles in r ...

*moderate: many large, plump, irregular nuclei, 1-2 mitotic figures *severe: obvious pleomorphism, enlarged bizarre nuclei with dense chromatin,

giant cells A giant cell (also known as multinucleated giant cell, or multinucleate giant cell) is a mass formed by the union of several distinct cells (usually histiocytes), often forming a granuloma. Although there is typically a focus on the pathological ...

, often

multinucleated Multinucleate cells (also known as multinucleated or polynuclear cells) are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinat ...

, enlarged, atypical

nucleoli The nucleolus (, plural: nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of sig ...

Mitotic figures

Evaluation of the mitotic figures in a STUMP requires evaluation of 3 specific criteria #Hairy extensions of chromatin must be present, extending from a central clot-like dense mass of

chromosomes A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

. Hairy extensions from an empty center favor a non-mitosis. Count 4 sets of 10 fields in the area of highest mitotic activity and use the highest count #No

nuclear membrane The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material. The nuclear envelope consists of two lipid bilayer membrane ...

#Rule out

lymphocytes A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adap ...

mast cells A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a par ...

, stripped nuclei, degenerated cells, and

precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

hematoxylin Haematoxylin or hematoxylin (), also called natural black 1 or C.I. 75290, is a compound extracted from heartwood of the logwood tree (''Haematoxylum campechianum'') with a chemical formula of . This naturally derived dye has been used as a h ...

Necrosis

Coagulative tumor cell necrosis is common in clinically malignant smooth muscle cell tumors. It consists of an abrupt transition between necrotic cells and preserved cells. Ghost nuclei from necrotic cells are often seen, but inflammatory cells are uncommon. Hyalinizing necrosis is more common in leiomyomas. It consists of a zone of hyalinized collagen between dead cells and preserved cells, commonly eosinophilic. If dead nuclei present, they are uniform and the chromatin is often. Necrosis secondary to ulceration in submucous leiomyomas features acute inflammatory cells and a peripheral reparative process, whereas ghost outlines of nuclei are usually inconspicuous or absent.

Algorithm

* Bell's criteria do not apply to extrauterine tumors * No or mild atypia, no tumor cell necrosis ⇒ leiomyoma. If 5 or more mitotic figures are present in 10 high powered fields but the behavior still appears benign, may append “with significant mitotic activity”. * Moderate to severe atypia without tumor cell necrosis ** atypical leiomyoma if < 10 mitotic figures per high power field or **

if ≥ 10 mitotic figures per high power field *Moderate to severe atypia and tumor cell necrosis ⇒

(mitotic figures don’t matter).

References

* * * * *

External links

{{Soft tissue tumors and sarcomas Types of cancer