SG12 A rare case of perianal granular cell tumour in a patient with localized recessive dystrophic epidermolysis bullosa

Abstract A 37-year-old Pakistani woman with localized recessive dystrophic epidermolysis bullosa (RDEB) presented with an 8-mm firm, ulcerated, tender, erythematous plaque at the 9-o’clock position of the anal margin. Initially diagnosed as a haemorrhoid, the lesion failed to improve with conservative measures, prompting a referral to colorectal surgery. Examination under general anaesthesia and a punch biopsy were subsequently performed. Histopathological biopsy analysis revealed fibrocollagenous tissue infiltrated by a tumour with focal surface ulceration. The tumour was composed of aggregates of large epithelioid cells with indistinct cell membranes, rounded-to-oval bland nuclei and abundant granular basophilic cytoplasm separated by thick collagenous stroma. Immunohistochemistry demonstrated strong positivity for CD68 and S100, negativity for melan-A and HMB45, and a Ki67 proliferation index of 1%. These findings were consistent with a diagnosis of granular cell tumour (GCT). Abdominal and pelvic computed tomography and magnetic resonance imaging scans were reassuring, revealing no additional masses, lymphadenopathy, organ infiltration or bone involvement. The GCT was subsequently widely excised with clear margins, as confirmed by histological examination. The wound site was left open to promote healing; however, this was complicated by concomitant RDEB resulting in persisting well-demarcated ulceration unresponsive to topical Oleogel-S10, mupirocin 2% and Trimovate®. Botulinum toxin injections, topical glyceryl trinitrate and diltiazem are now being considered as the next step for this patient, with the aim of encouraging skin healing by relaxing the anal sphincter muscle. GCTs are rare, typically benign neoplasms accounting for < 1% of all soft-tissue tumours, and mostly arise on the head and neck. Only 1–2% are malignant in nature. They rarely present in the perianal region, with fewer than 30 such cases in the existing literature. Perianal GCTs may be overlooked in favour of more common differentials such as haemorrhoids, fissures and abscesses. Localized RDEB further compounded the diagnostic difficulty in this case, as the perianal region is inherently subject to mechanical trauma during defecation, and therefore also commonly affected by blistering and ulceration characteristic of RDEB. This case highlights the importance of a low threshold for biopsy when diagnosing GCT, especially when standard treatments fail to elicit improvement. Additionally, this case presents the importance of tailored examinations under anaesthesia to facilitate perianal diagnoses in patients with EB, where skin fragility and pain limit the feasibility of routine examination methods. This case joins the existing literature that reports the challenges of wound healing in EB postoperatively, but importantly suggests that future management of other, nonsurgical perianal wounds in EB could also utilize similar techniques involving therapeutic anal sphincter muscle relaxation.