What the pyogenic granuloma hides

Abstract

A 10-year-old male was referred to our outpatient dermatological clinic complaining of a lesion with vascular characteristics on the right thigh of 2 months of evolution (Fig. 1A). The lesion was asymptomatic but bled with minimal trauma. Dermoscopic study revealed purplish and reddish lacunae with slight hyperkeratosis in the lower pole without melanocytic structures (Fig. 1B). The double rail sign was not appreciated (This sign comprises white lines that correspond to the histologic finding of fibrous septa that surround the lobules). Clinical diagnosis of pyogenic granuloma was stated, and a biopsy was performed. The histological report revealed a lesion made up of rounded cells and epithelioid to a lesser extent that affects papillary and reticular dermis (Fig.1C), ulcerated epidermis and significant inflammatory infiltrate and a high number of mitoses (9 mitoses/mm2) (Fig. 1D). Immunohistochemistry revealed Ki67 greater than 70% and HMB45 intensely +. What is your diagnosis and how to manage this case? (Answer on page ••) We concluded the diagnosis of Spitzoid Melanoma pT3b. A massive DNA and RNA sequencing study of genes associated with familial melanoma was performed, being negative. The case was discussed in the Multidisciplinary Committee and Sentinel Lymphatic Node Biopsy (SLNB) was performed with a negative result. Six months after the SLNB, the patient remains disease-free. Spitz nevus (SN) is a melanocytic neoplasm of epithelioid or spindle cells first described in 1910 by Darier and Civatte and characterised in 1948 by Spitz under the name of Juvenile Melanoma. It was described as a melanocytic tumour, present in childhood, with clinical and pathological characteristics similar to a melanoma but with a benign behaviour.1 Melanocytic neoplasms with a spitzoid morphology include a spectrum of progression between benign and malignant lesions. In recent decades, there has been a tendency to classify them into 3 types, sometimes difficult to distinguish from each other: conventional NS, atypical Spitz tumour (AST) and spitzoid melanoma (SM).2 SM is relatively rare in paediatric patients and has a favourable prognosis. Scientific evidence is supported by a retrospective series of patients who identify a low prevalence of death from this cause in the period 1949 to 2006 (25 fatal cases).3 The incidence of childhood cutaneous melanoma in the USA was 0.3–0.4% in patients less than 10 years old.4 From a clinical point of view, SM is usually presented as amelanotic lesions, which are frequently ulcerated with serous crusts. It is not uncommon for the clinician to raise the following as differential diagnoses: infantile haemangioma, pyogenic granuloma, xanthogranuloma or basal cell carcinoma (extremely rare in paediatric age). Therefore, the biopsy is mandatory. Concerning the complementary tests, histological examination remains the gold standard. Histopathology shows atypical melanocytic nests with fusiform or epithelioid morphology with a hyperchromatic and pleomorphic nucleus. The main immunohistochemical markers used to differentiate its malignant character are HMB45 and MIB-1. The use of genomic tests to assist in the diagnosis of SM has been expanded in recent years,5 helping us to understand and characterise it. Copy number abberations through FISH or CGH are increasingly been used to assist in its diagnosis. The main associated controversy arises in the positioning of the selective biopsy of the sentinel node in contrast to the adult population due to the high number of positive cases with good evolution. A series of 10 paediatric patients with SM treated by complete excision and without SLNB revealed, after a mean follow-up of 3 years, that all patients were disease free. In conclusión, MS is a rare disease that requires a different approach compared to adult melanoma. There is a propensity for SM to metastasize to local lymph nodes but not distant sites. Although there have been reports of late recurrence, we would like to emphasise that involvement with a multidisciplinary team is essential and an appropriate clinical long-term follow-up is important.6