Every day, bits of human tissue are removed by Pentucket Medical physicians for examination by pathologists.
Many of these studies will rule out the presence of disease, while others lead to life-saving interventions.
Much of what sets the stage for these outcomes takes place in a small suite on the first floor of our Haverhill office. The Pentucket Medical Histology Lab is a busy and thriving section of our medical service, a world of hot wax and colorful dyes, where tiny biopsies are processed and preserved so that pathologists can rule in or rule out the presence of disease.
The workday in the histology lab begins at 5 a.m., says Diane Santana, the histology lab’s manager.
“When endo starts their day, we start our day,” she says, referring to Merrimack Valley Endoscopy Center, a first-floor neighbor that is histology’s main source of the specimens that make up the lab’s workday.
Diane and her colleague Linda O’Brien are the key link between examining doctors who spot potential trouble and the pathologists who make the call on whether there is truly a problem. Their workdays are continuous round of interaction with endoscopy clinicians, couriers, pathologists and highly specialized equipment.
“They are really an essential gear in our operation,” says Dr. Tom Fazio. “They enable us to provide results to our patients much more promptly, which wouldn’t be possible if we had to outsource the work that’s being done right here.”
“High quality histology is crucial to accurate pathological diagnosis,” says Dr. George Kwass, a Haverhill-based pathologist who interacts on a nearly daily basis with Pentucket’s histology service. “Pentucket Medical is fortunate to have such a high quality histology laboratory with state of the art equipment and talented histotechnologists.”
Work in the histology lab seems to combine science, artistry, craftsmanship and something like the organizational skill of a librarian. In regards to the latter, keeping the specimen linked to the name of the patient from whom it came is a tremendous priority.
“When we receive a specimen it has the patient’s name on it and it also comes with a requisition slip,” Linda says. “We assign a number to the sample. At this point the sample is in a tiny jar, and this, along with the requisition slip and an empty cassette, marked with our number, goes into a plastic bag. The whole package goes into a bin for the courier to bring to the hospital, which is the first time the pathologist will see it.”
As a rule, the pathologists see each sample two times. Their first examination of the specimen records a description of the specimen as it looks to the naked eye. This is
the "gross exam", and it serves mostly to produce a general description that can be used if there is a question of specimen mislabeling.
After gross examination, the samples are couriered back to histology and prepared for a later examination by the pathologist, under the microscope.
On return to the histology lab each sample begins to make its way through a series of machines. The first step is to “fixate” the specimen with a formaldehyde solution in order to keep it from decomposing. Next water is removed from the tissue, which is then replaced, or “infiltrated,” with hot wax. In this step, the sample and the cassette containing it are placed in a machine called an embedder. Here the cassette and the sample inside is encased in hot paraffin.
Wax is big part of the histology environment, and the chairs near the embedder are sheathed in a generous coat of paraffin. The stuff is innocuous, but as Diane and Linda point out, “You don’t come to work in histology wearing nice clothing!”
After the wax in the cassette is set up around the sample, it is placed in a third machine, called a Microtoner.
This cutting machine shaves a 4-microns-thin slice of the wax-embedded specimen. The result is a ribbon that the histologist tweezers into a bath of warm water, on which it floats like a feather. Linda slips a glass slide under the ribbon, and the specimen gently flattens onto the glass.
The slide is given the same number as the block. For obvious reasons, cataloguing and tracking specimens is an obsessive focus of quality control in the histology lab.
Next step is the “stainer” the robotic arm of which first removes excess wax by dipping into a solvent bath. This dunking is the first of as many as 18 such immersions that the sample will undergo during the next hour. The procedure, which the histologists once performed by hand, is somewhat like the darkroom process by which photographic prints are made. The robotic arm of the labs new machine dips the specimen into little vats of colored liquid that are arranged in rows. Each vat contains a different alcohol solution intended to dye different parts of the tissue cells in contrasting colors.
After one final dehydration, the specimen is cover-slipped with glass, and returned by courier to the pathologist at the hospital.
On a typical day, upwards of a hundred slides are prepared in this way. And this volume is predicted to grow, says Diane, who has been with the lab for 4 years. Linda, who has worked there on a per diem basis for nearly three years, just signed on as a full-time staffer. According to Diane, new equipment and more histologists will soon be bolstering the output of this unique and productive section of our clinical operation.
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