Copy Number Alterations of SCC Arising in HS
Hidradenitis suppurativa (HS) is a chronic inflammatory condition affecting the apocrine glands of the axilla, inguinal, or anogenital areas often leading to recurrent abscesses and fistulous tracts . Squamous cell carcinoma (SCC) is a very rare, but clinically aggressive complication with a high mortality rate. SCC can be difficult to distinguish histologically from its reactive, benign counterpart (pseudoepitheliomatous hyperplasia, PEH) which is frequently seen in HS. Copy number assessment was performed on cases of SCC (malignant) arising in HS and cases of PEH (benign) arising in HS. The aim was to identify any recurrent changes that could be used diagnostically or for future research. Retrospectively, 5 cases of SCC arising in HS and 4 comparison cases of chronic HS with benign, PEH were identified through institutional Mayo Clinic medical records (1978-2011). All cases of SCC arising in HS had a documented history of HS with subsequent surgical resections which demonstrated SCC. The comparison group (benign HS) all had > 10 years of follow up with no prior history of cancer. Hematoxylin and eosin stained tissue slides were obtained with available tissue from Mayo Clinic’s internal tissue registry. The slides were reviewed and a diagnosis of SCC or benign HS was confirmed along with other histologic characteristics by a board certified dermatopathologist. Copy number alterations were assessed via single nucleotide polymorphism microarray (OncoScan, Applied Biosystems) on formalin-fixed paraffin embedded tumor tissue . Histologically, all cases showed features of invasive squamous cell carcinoma, ranging from well (minimal cytological atypia and lack of highly infiltrative growth pattern) to moderate differentiation (unequivocal cytological atypia and infiltrative growth pattern). No poorly differentiated areas or sarcomatoid features were observed. All patients died of their disease, with four patients succumbing within a year after the diagnosis, and one locally recurrent case died 4 months after the onset of recurrence (Table 1). Extensive CNAs were identified in 4 of 5 cases, all of which demonstrated moderately differentiated histology. EGFR gene gain (chromosome 7p) and CDKN2A loss or loss of heterozygosity (chromosome 9p) were recurrent changes identified, each detected in 3/4 and 4/4 cases, respectively. The last case (case 5) was an invasive well differentiated SCC with early bone destruction and rapid clinical deterioration, which however did not demonstrate any CNAs. The comparison group of 4 patients with benign HS and PEH showed either normal genomic copy number findings or small change of undefined significance (Figure 2) (Table 1). Finally, HPV infection was not detected in these cases of SCC via a previously published study .