Therapeutic Excision of Hidradenitis Suppurativa with Immunoblastic Component: Occam’s Razor or Hickam’s Dictum?

Summary: Patients with chronic hidradenitis suppurativa (HS) have an increased risk of secondary malignancies. Effective HS therapies such as TNFa inhibitors putatively increase this risk. An HIV positive adult man with 20 year history of HS, Hurley Stage III being treated with adalimumab underwent therapeutic excision of a recurrent, gluteal HS lesion. The excision showed an area exhibiting large atypical CD30+ lymphocytes with prominent vesicular nuclei and prominent nucleolation expressing B-cell markers (CD20+/PAX5+/CD79a+/MUM1+/BOB1+/OCT2+) with elevated Ki-67 proliferative index. These changes were notable but not diagnostic of plasmablastic lymphoma. HHV8 and T. pallidum immunohistochemical stains were negative. In situ hybridization for Epstein Barr virus (EBER) was negative. Furthermore, there was no evidence for amyloid deposition nor micro-organisms with Congo Red, GMS, PAS and Fite stains. There was no clinical evidence of recurrence at 1 year follow up. HS lesions can be complicated by development of secondary malignancies, squamous cell carcinoma being most commonly reported. However, cases of metastatic adenocarcinoma and plasmablastic lymphoma have also been observed in stage III HS patients' new or worsening lesions. The setting of immunosuppression likely represents a risk factor. Thus, even when presented with excisional HS specimens, the dermatopathologist must always be open to a secondary diagnosis.