Table 1.

Clinical characteristics of patients and histologic features of the lesions.

Patient	Sex (age in years)	Smoker	Hurly Stage	Duration of HS (years)	Previous treatments for HS	Location of Cancer	Macroscopic appearance	Histology	HPV	Surveillance	Comments
1	Female (73)	Yes	?	?	?	Vulva	6.2 × 6 cm tumor in the anterior region of the vulva, affecting labia mayor and minor of both sides.	Keratinizing and well-differentiated squamous cell carcinoma over foci of hidradenitis suppurativa with abscesses and scarring fibrosis. Depth of infiltration: 14 mm.	–	Free of relapse 6 months after surgical intervention	No nodal involvement or distant metastases
2	Male (60)	Yes	III	35	Antibiotics Metformin Surgery	Gluteal region	Multiple fistulae with fibrosus scars all over gluteal region. In the inferior pole of the right buttock there is an 8×4 cm hyperkeratotic and ulcerated nodule	Multiple epidermal fistulae with surrounding mixed inflammatory infiltrate and areas of fibrous scarring are seen. In various foci, well-differentiated squamous cell carcinoma nests can be observed arising from these fistulae. Various corneal pearls and pseudoepitheliomatous hyperplasia are seen.	–	Died due to infectious complications of the HS 3 months after surgery of the SCC	Sacral and pelvic osteomyelitis, epidural empyema, bacterial meningitis, and bacteriemia secondary to sacral and gluteal abscesses No nodal involvement or distant metastases
3	Male (63)	Yes	III	41	Antibiotics Retinoids Corticosteroids Metformin Secukinumab (last 10 months) CO2 laser Surgery	Gluteal region	Indurated erythematous plaque with multiple subcutaneous abscesses and fistulae affecting both buttocks and intergluteal region	Numerous cavities and fistulae with surrounding inflammation and fibrosis. Multiple foci of well differentiated squamous cell carcinoma can be seen arising from cavities and fistulae, affecting dermis and hypodermis.	–	Free of relapse 9.5 months after the surgical intervention	No nodal involvement or distant metastases
4	Female (62)	Yes	?	?	?	Right inguinal region	Ulcerated greyish plaque of 9.7 × 4 cm with surrounding erythema, suppurating fistulae, and fibrous scars	Solid basal cell carcinoma	?	Free of relapse 22.5 months after the surgical intervention

Abbreviations: HPV: human papilloma virus; HS: hidradenitis suppurativa; SCC: squamous cell carcinoma; ?: Unknown; –: negative.