The girl at the centre of this case was nine years old, had Turner syndrome and a lump in her neck. What began as a solitary thyroid nodule ended up being something pathologists come across only every so often: a myofibroma, a benign tumour built from fibroblasts and myofibroblasts, sitting in the thyroid of a child with Turner syndrome. The team that treated her reports it in Pediatric and Developmental Pathology and flags a detail that matters: no previous case of this combination has ever been described.
The first step was fine-needle aspiration, the test that in clinic helps make sense of almost any thyroid nodule. The result was inconclusive: a proliferation of spindle cells —elongated, tapering cells— suspicious for a process arising outside the gland. That is exactly where the trap lies. Most thyroid nodules are epithelial, meaning they grow from the tissue that actually makes the hormones; primary mesenchymal tumours of the gland are exceedingly rare, and under the microscope they look like other spindle-cell lesions that really are malignant or that come from nearby structures. Cytology, so useful in ordinary cases, was not enough this time.
What the pathologist saw
A lobectomy —removal of half the thyroid— was performed, and examining the whole specimen changed the diagnosis. The tumour was a well-circumscribed, unencapsulated nodule made of bland-looking myofibroblastic cells arranged in fascicles within a collagenous stroma. The immunohistochemical profile was consistent with myofibroma. Final confirmation came from targeted molecular testing: a pathogenic variant in PDGFRB plus a novel variant of uncertain significance. PDGFRB encodes a growth-factor receptor involved in myofibromatosis, so finding a functional alteration there supports the diagnosis and hints at why this tissue proliferates.
Two lesions of the same lineage in one child
What makes the case unique is not only the neck. Five years earlier, at the age of four, the same patient had a myofibroblastic proliferation in the parotid gland. Two lesions of the same cell lineage, in different locations and separated by years, in a girl with Turner syndrome. The authors do not claim a causal link: they speak of possible shared pathogenetic mechanisms and leave the question open for further cases. It should be read that way, as an observation rather than a warning. What is well established is that people with Turner syndrome have thyroid disease more often, particularly autoimmune forms —Hashimoto’s thyroiditis is the commonest— and that blood tests and ultrasound are part of their routine follow-up; that is why a nodule gets found and investigated in good time.
What it changes in the clinic
The practical message is about pathology, not alarm. When cytology shows spindle cells in the thyroid, rare benign entities belong on the list and the label of malignancy should not be rushed; and for a nodule in a girl with Turner syndrome the sensible route is unchanged: ultrasound, aspiration when indicated and, when cytology does not fit, diagnostic surgery with full examination of the specimen. The authors themselves argue for an integrated approach —cytomorphology, immunohistochemistry and PDGFRB-focused molecular analysis— to avoid misclassifying these lesions.
The limits are those of a single case: it describes what happened in one patient and cannot tell us how many girls with Turner syndrome will develop anything similar, nor does it prove the X chromosome is to blame. Nor is there long-term thyroid follow-up after the lobectomy beyond what the case itself documents. It does serve two concrete purposes: reminding pathology departments that thyroid myofibroma exists and can turn up in this context, and putting on record that repeated myofibroblastic proliferations in the same child deserve a genetic look. If a daughter with Turner syndrome ever has a nodule removed and the report mentions “spindle cells”, the right question is not how frightened to be, but whether the specimen has been studied with immunohistochemistry and, if needed, molecular testing.
Source: Thyroid Myofibroma in a Child With Turner Syndrome: Integrated Cytologic, Histopathologic, and Molecular Characterization. Manukyan I, Rossi CT, Vaidyanathan P, Mudd PA, Sirotnikov S. Pediatric and Developmental Pathology 2026;29(6):710-715. DOI: 10.1177/10935266261452369.
Read the paper: https://doi.org/10.1177/10935266261452369 · PubMed 42210516
