When you have surgery to remove a tumor — even if it’s a totally common uterine fibroid tumor — the number one thing you’re waiting to hear is whether it was cancerous or not.

But what many people don’t realize is that even in this day of high-tech pathology labs, it’s not always easy to classify tissue as being distinctly malignant or benign. In fact, in some rare cases, doctors really can’t determine for sure whether or not cancer is present.
Cancer isn’t always obvious

Whenever something is surgically removed from someone, that tissue isn’t just immediately incinerated. Instead, it finds its way to a pathologist, who will examine it with the naked eye as well as under a microscope, often looking to detect any cancer. (Surgical pathology is defined by The Johns Hopkins Hospital as “the study of tissues removed from living patients during surgery to help diagnose a disease and determine a treatment plan.”)

woman examining tissueBut here’s where it gets complicated: Some unusual tumors show signs of being cancerous as well as indications of being benign.

This is not normal, based on what doctors and scientists know about cancer so far. The vast majority of the time, it’s pretty clearly one or the other.

You could think of it kind of like a light switch: it’s on or it’s off. But in the case of certain “tumors of uncertain malignant potential,” it’s more like the light switch might be on or could be off… but there’s no way to tell because the lightbulb is missing.

When that happens, it’s impossible to state definitively whether someone is at risk of cancer spreading through her body, or if she can be safely be given a clean bill of health.

Tumors of uncertain malignant potential

Most commonly (and that’s a relative term), this kind of mysterious diagnosis is related to a uterine tumor, and is called a “smooth muscle tumor of uncertain [unknown] malignant potential” — shortened to the ugly acronym STUMP.

This I know not just from reading scores of research papers or talking to doctors, but because I got the frustrating and worrisome diagnosis myself.

stump diagnosis pathology

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>> The hysterectomy story: An adventure in two parts

Rare, but not unknown

My first response, of course, was to scour the web for information about this rare creature.

Pathology research published in 2011 by the Indian Journal of Pathology and Microbiology noted, “Uterine smooth muscle tumors of uncertain malignant potential (STUMP) are uncommon tumors. They are unclassifiable by current criteria as unequivocally benign or malignant.”

In 2012, a study in the Journal of Research in Medical Sciences stated, “One of the most controversial concepts on the subject of uterine smooth muscle tumors is smooth muscle tumor of uncertain malignant potential (STUMP), a term first used by Kempson in 1973. These are a group of heterogeneous and uncommon uterine smooth muscle tumors which fulfill some but not all the diagnostic criteria for leiomyosarcoma.”

“Histological diagnosis is challenging and usually problematic,” said a case report from 2012 published in the Indian Journal of Medical and Paediatric Oncology. The authors added, “Natural history of the disease as well as the malignant potential remains uncertain. They are usually clinically benign but, in some cases, recurrence can occur many years following hysterectomy.”

Rare tumors aren’t unique to the uterus, however. The same kind of ambiguous tissue can appear elsewhere in the body.

For example, there’s a similar STUMP diagnosis in men for “stromal tumors of uncertain malignant potential” found in the prostate, while “melanocytic tumors of uncertain malignant potential” (MELTUMP) are essentially skin moles that are puzzling. “Thyroid tumors of uncertain malignant potential” have been dubbed TT-UMP, while “glomus tumors of uncertain malignant potential” earned the nearly-unpronouncable nickname GTUMP.

Very little to go on

Typically, physicians review medical research, case studies and existing pathology reports to review and learn about issues they see in practice. But because tumors of this type are so unusual, there is very little information about them in the medical literature, leaving most doctors at a loss.

Uterine smooth muscle tumor with mild mitotic activity (smooth muscle tumors of uncertain malignant potential tumor) via the  Indian Journal of Medical and Paediatric Oncology

Uterine smooth muscle tumor cells with mild mitotic activity (smooth muscle tumors of uncertain malignant potential tumor) under a miscroscope, via the Indian Journal of Medical and Paediatric Oncology

In the words of the the authors of a 2009 analysis published in The American Journal of Surgical Pathology, “STUMPs represent a heterogeneous group of rare tumors that have been the subject of only a few published studies, some of which lack detailed clinicopathologic details and/or follow-up data.”

So deep is the void that Dr Anais Malpica, director of the Gynecologic Pathology Fellowship Program at the MD Anderson Cancer Center in Texas, made it a topic of discussion at a major pathology meeting in August 2012. The title of her presentation? “Uterine Smooth Muscle Tumors that Nobody Wants to Talk About.”

Of benign-appearing smooth muscle tumors in the uterus and other anatomical sites, she writes, “They can represent a true paradox and a management challenge.”

Help for the layperson

While medical professionals have very little data with which to work, there’s practically nothing out there for patients who have been given a STUMP diagnosis.

Sifting through the medical research can be a daunting task — not to mention that not every outcome described is hopeful.

The aforementioned 2009 analysis stated that STUMPS “are usually clinically benign but should be considered tumors of low malignant potential because they can occasionally recur, in some cases, years after hysterectomy,” and added, “Patients diagnosed with STUMPs should receive long-term surveillance.”

That’s why almost all patients with STUMPS are asked to see a gynecologic oncologist at regular intervals — every six months or so seems typical.

Follow-up surgery may also be advised to remove at-risk tissue. For example, if you had a fibroid removed and it ended up being a STUMP, a hysterectomy might be recommended. In my case, I had a sub-total hysterectomy, which left the cervix behind.  Three months later, I was back in the operating room for an even more complex surgery to remove all traces of my uterus.

The checkups and surgeries are all part of the “be on the safe side” medical plan, which is the best anyone can do for now.

“In these tumors, it is simply impossible with current tools to predict the behavior with certainty, and this makes their management difficult. What makes the management more complicated is the difficulty in counselling patients with regards to the likely clinical behavior,” reads another 2012 report published in the Journal of Research in Medical Sciences.

“However,” they say, “data from literature suggest a low risk of recurrence and a generally good clinical outcome.”

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For further insight, see two STUMP pathology reports on the next page


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