Follicular squamous cell carcinoma rates ‘underestimated’
medwireNews: Rates of follicular squamous cell carcinomas (SCC) are underestimated, suggest results from a study published in the British Journal of Dermatology.
"Recognition of this under-reported form of SCC is essential if an inappropriate diagnosis of metastatic SCC, with potentially harmful and inappropriate therapy and investigation, is to be avoided," say Igor Shendrik (University of Oklahoma, Tulsa, USA) and colleagues.
This issue arises as it can be very difficult to distinguish follicular SCCs from metastatic SCC as they appear almost identical on histological investigation.
To estimate how common follicular SCCs are, Shendrik and team analyzed data collected from 5212 cutaneous SCCs over a 5-year period.
They found that 61 of the cutaneous SCCs in 60 patients were of follicular origin and were mostly located in the head and neck region. Of these, 49 were "pure" follicular SCCs, defined as "deriving from a pre-existing hair follicle structure," and 12 were "hybrid" lesions, defined as having a partial interfollicular epidermal origin.
No signs of metastases were observed in any of these patients, despite 40 tumors having positive margins when originally biopsied. The team says that the true invasion depth of these tumors is less than initially apparent, and adds that "the clinical course of this carcinoma suggests a relatively indolent biological behaviour."
More men in the study had follicular SCCs than women, at 44 cases versus 16, and the mean age of the patients was 74 years. There were no apparent differences between people with hybrid and pure follicular lesions.
A central keratinizing cavity was a common feature of these follicular SCCs, seen in 37 pure and eight hybrid cases while around 50% (25 pure; 6 hybrid) of the patients with follicular lesions had "areas of clear cell cytologic changes of ground glass type, consistent with trichilemmal differentiation," the authors report. Basaloid atypia was also seen in 22 tumors.
The researchers estimate that 1.2% of all primary SCCs are at least partly follicular. They emphasize the importance of recording the structure of origin of these lesions due to the extremely similar histological nature of follicular SCCs and metastatic SCCs.
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By Helen Albert, Senior medwireNews Reporter