Storiform describes a pattern in which cells are arranged in short, crisscrossing bundles. The pattern looks like a woven mat or the spokes of a wheel. The word comes from the Latin storea, meaning a woven mat. The cells that form this pattern are usually long, thin spindle cells.
Storiform is a description of what the pathologist saw under the microscope, not a diagnosis on its own. The pattern is seen in both noncancerous and cancerous conditions. It is most often described in skin and soft tissue tumors, such as a dermatofibroma. This article explains what a storiform pattern looks like, where it is found, and what it means in your pathology report.
What does a storiform pattern look like under the microscope?
In a storiform pattern, groups of spindle cells run in short bundles that cross over and weave between each other. In some areas, the bundles radiate out from a central point, like the spokes of a cartwheel. The overall effect looks like woven fabric or a straw mat.
The pattern is easiest to see at low magnification, when the pathologist can view a large area of tissue at once. It is visible on routine hematoxylin and eosin (H&E) slides, so no special test is needed.
Where is a storiform pattern found?
A storiform pattern can be seen in several different conditions. Common examples include:
- Dermatofibroma. A dermatofibroma is a common noncancerous growth in the skin. It often shows a storiform pattern, usually mixed with other cell types.
- Dermatofibrosarcoma protuberans. Dermatofibrosarcoma protuberans (DFSP) is a slow-growing skin cancer. It typically shows a tightly packed storiform pattern that extends deep into the subcutaneous fat.
- Undifferentiated pleomorphic sarcoma. Undifferentiated pleomorphic sarcoma is a type of sarcoma, a soft-tissue cancer. Some tumors of this type contain storiform areas mixed with very abnormal cells.
- IgG4-related disease. In IgG4-related disease, an immune condition, scar tissue often forms in a storiform pattern. Pathologists call this storiform fibrosis.
A storiform pattern can also be seen in some nerve tumors and in other soft tissue tumors. Because the same pattern appears in so many conditions, pathologists never use it alone to make a diagnosis.
How is a storiform pattern identified?
A pathologist identifies a storiform pattern while examining the tissue under the microscope. The pathologist notes the pattern as one of several features that help narrow the diagnosis.
To reach a final diagnosis, the pathologist also considers how abnormal the cells look, how deep the growth extends, and the results of any additional tests. Immunohistochemistry is often used to tell apart tumors that share a storiform pattern. For example, a dermatofibroma and dermatofibrosarcoma protuberans can look similar, but they usually show different results for markers such as CD34 and Factor XIIIa.
What does a storiform pattern mean for me?
The meaning of a storiform pattern depends entirely on the final diagnosis. On its own, the word does not mean that a growth is noncancerous or cancerous. Your report will list the diagnosis separately, and that diagnosis determines what happens next.
Questions to ask your doctor
- What is the final diagnosis in my report?
- Is the growth noncancerous or cancerous?
- Why was the storiform pattern mentioned in my report?
- Were additional stains such as CD34 or Factor XIIIa done?
- Was the growth completely removed?
- Could this growth come back after removal?
- Do I need any further treatment or follow-up?
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