Pain without palpation may be a clue to differentiate invasive squamous cell carcinoma (SCC) from actinic keratoses (AK), an Australian study has shown
Dermatologists in three practices in Sydney and Melbourne investigated the frequency and nature of pain associated with 190 consecutive cases of AK suspected of being SCC, 299 cases of intraepidermal (IEC) SCC and 853 cases of invasive SCC.
As expected, pain frequency was found to increase on the spectrum from AK to invasive SCC and also with larger diameter and deeper invasive SCC.
Pain with palpation was recorded with 15.8% cases of AK, 15.1% of IEC and 29.0% invasive SCC. Pain without palpation was recorded in 1.1%, 4.0% and 6.7% cases of AK, IEC and invasive SCC, respectively.
The researchers, led by Dr John Pyne of the Prince of Wales Clinical School, University of NSW, noted that pain frequency for SCC was relatively constant (around 30%) up to a 2mm invasion depth.
Beyond an invasion depth of 2mm the pain frequency progressively escalated to 60% for invasion depths over 4mm.
“This finding indicates pain may be a useful clinical clue to SCC with deeper invasion beyond 2 mm,” they wrote in Clinical and Experimental Dermatology.
They also found the average invasion depth for SCC on the ear (1.9mm) and lip (1.7mm) exceeded the average depth (1.5mm) for the remaining head and neck sites in these early disease cases.
Pain did not vary significantly by the grade of differentiation in males, but did in females. In females, pain was recorded in 45.4% of cases of well differentiated SCC and 9.1% of poorly differentiated SCC.
Acantholytic SCC, which has been controversially linked to higher risk, was found to be more pain prone than non-acantholytic SCC (48.7% vs 35.2% recorded pain.
However, an absence of pain does not exclude acantholysis or perineural invasion (PNI) from an SCC, they emphasised.
The study had only a small number of cases of PNI, of which three of the five cases (60%) recorded pain.
The study authors concluded that “although infrequent, pain without palpation is an indicator for invasive SCC” as it was a more specific clue to invasive SCC than pain with palpation.