An Ulcerated Nodule on the Scalp

A 58-year-old man presented to the dermatology department with a 2-year history of an erythematous nodule on the right parietal area of the scalp. The lesion initially appeared as a papule and progressively increased in size. One month prior to his presentation to the clinic, the nodule ulcerated and started bleeding. On examination, the nodule was 3 × 3 cm in size, well demarcated, ulcerated and bleeding (Figure 1). There were no palpable regional lymph nodes, and the remainder of the physical examination was unremarkable. A punch biopsy from the nodule was taken (Figure 2). Porocarcinoma (malignant poroma). Histopathological examination of the biopsy showed marked hyperkeratosis and epidermal acanthosis with multiple tumour nests in the dermis (Figure 2a), with some of the tumour lobules connecting to the epidermis (Figure 2b). On higher magnification, the tumour nests demonstrated uniform epithelial cells, central necrosis, multiple atypical cells with large hyperchromatic nuclei and duct-like structures (Figure 2c,d). Immunohistochemical analysis of the biopsy revealed positive CK, EMA and Ki-67 (Figure 3). The clinical findings, histopathological examination and immunohistochemical analysis supported the diagnosis of porocarcinoma. The patient underwent wide local excision with clear surgical margins followed by skin grafting. He was on regular follow-up with the oncology team with an ultrasound of the regional lymph nodes, which were repeatedly negative. The patient presented to us again 3 years after with a 1-year history of a painless erythematous nodule on the right temporal area on the scalp near the skin graft. The nodule was well demarcated, measuring 3 cm in diameter, non-tender, with a smooth surface (Figure 4). No palpable regional lymph nodes were found on physical examination. A punch biopsy from the nodule was performed, which showed similar findings and immunohistochemical features as the previous tumour, thus confirming the diagnosis of recurrent porocarcinoma. Porocarcinoma is a rare appendageal malignancy, accounting for 0.005%–0.01% of cutaneous neoplasms [1]. The mean age at diagnosis is from 62 to 76 years. Porocarcinoma presents as an erythematous firm nodule or plaque [2]. It is most commonly located in the lower limbs, head and neck. It can either develop de novo or in a preexisting poroma. Signs of malignant transformation include spontaneous bleeding, ulceration, itch, pain and sudden growth [1]. Risk factors for developing porocarcinoma include high UV exposure and immunosuppression. The diagnosis of porocarcinoma is challenging because of its rarity and requires clinicopathological correlation. Main differential diagnoses include squamous cell carcinoma, poroma and other adnexal tumours [3]. Histopathological findings may show a tumour with infiltrating growth pattern, malignant cells with hyperchromatic atypical nuclei with mitoses, ductal structures and central necrosis [4]. On immunohistochemistry, porocarcinoma is positive for EMA, CK 5.6, CK7 and P63. Carcinoembryonic antigen (CEA) highlights ductal differentiation and can be positive in about 77% of cases of porocarcinoma [5]. Lymph node metastasis is seen in up to 20% of patients with porocarcinoma, whereas distant metastasis is detected in about 14.5% of patients. The most common areas for distant metastasis are the lungs, liver, brain and skin [1]. Treatment of porocarcinoma is mainly surgical with wide local excision or Mohs micrographic surgery. Recurrence rate after surgical treatment is up to 20%. Some studies reported the use of adjuvant radiotherapy or chemotherapy in patients with metastasis [1]. Zainab Asghar: conceptualization, manuscript writing and editing, investigation and diagnosis. Humoud Al-Sabah: conceptualization, investigation and diagnosis, data curation. Atlal Allafi: supervision. The authors have nothing to report. The patient has given written informed consent for participation in the study and the use of their de-identified, anonymized, aggregated data and their case details (including photographs) for publication. Ethical Approval: not applicable. The authors declare no conflicts of interest. Data sharing is not applicable to this article as no new data were created or analysed in this study.