The phrase "are a small subset" is correct and usable in written English.
It can be used when referring to a specific group that is part of a larger category or population.
Example: "The species we studied are a small subset of the diverse flora found in the region."
Alternatives: "represent a minor portion" or "constitute a limited group".
"Even within the kinds of cancer where such a link is known, the genetically linked ones are a small subset.
And keep in mind, those 200 are a small subset of the total number of companies that are trying to get onto the calendar to pitch.
Lightning injuries are a small subset of electrical injuries and are responsible for an average of 300 injuries and 100 deaths per year in the US.
The data used here are a small subset of already partially published data in previous experimental studies [15, 22, 61, 62].
Side population (SP) cells are a small subset of cells isolated from a cultured cancer cell line that exhibit characteristics similar to those of cancer stem cells (CSCs), such as high metastatic and tumorigenic potential.
These highly conserved scaffolds are a small subset of the total scaffolds with homologs in two or more YNP metagenomes (~6.6% of 659,351 scaffolds, with the remainder of scaffolds having only 30 50% DNA identity).
"Malevolent behavior is a small subset," said Jay Doolan, assistant commissioner of the New Jersey Department of Education.
A positive database containing all the data in question would be a small subset of those combinations.
Among the condos is a small subset of superluxury buildings like 101 Warren Street and 7 Hubert Street, brokers said.
Such a census, "which was deliberated at the highest levels," is a small subset that is nonetheless informative and comparable from one year to the next, he said.
In fact, he sometimes defines "white people" in opposition to "the wrong kind of white people," because his true target is a small subset of white people, a white cultural élite.
