DP21 A rare case of immature teratoma arising from the central chest wall

Abstract A 39-year-old woman with Fitzpatrick type V skin, hidradenitis suppurativa Hurley stage 3 and extensive keloid scarring presented with a painful, rapidly enlarging, ulcerated, exophytic nodule on the central chest. This was initially suspected to be an inflamed keloid but was excised to exclude a squamous cell carcinoma. Histology revealed an infiltrative tumour with immature neuroectodermal-type tissue. The tumour was comprised of a disorganized mixture of tissues from all three germ cell layers: ectoderm (including keratinizing squamous epithelium with associated adnexal components including follicular and sebaceous-type elements in addition to glial tissue), mesoderm (including areas of bone, cartilage and smooth muscle) and focal endoderm (including ciliated respiratory-type epithelium). This was consistent with a teratoma with transformation to embryonic neuroectodermal tumour and lymphovascular invasion, and was positive for glial fibrillary acidic protein (GFAP) and OCT3/4. Histology from a biopsy of a right cervical lymphadenopathy demonstrated that the lymph node was almost entirely replaced by the germ cell tumour with somatic transformation to pure embryonic neuroectodermal tumour. This metastasis was positive for synaptophysin, CD56, GFAP and OCT4, with high Ki67 (about 50%). Computed tomography of the abdomen and pelvis showed no evidence of ovarian or mediastinal malignancy. Alpha-fetoprotein and human chorionic gonadotropin were normal. To our knowledge this is the first reported case of a cutaneous immature extra­gonadal teratoma arising on the central chest wall. Teratomas are tumours composed of three germ cell layers: ectoderm, endoderm and mesoderm. They account for 10% of all germ cell tumours (Moraru L, Mitranovici ML, Chiorean DM et al. Immature teratoma: diagnosis and management – a review of the literature. Diagnostics 2023; 13: 1516). They may be mature (benign and also known as dermoid cysts), immature (malignant) or monodermal (usually benign). Immature teratomas more commonly arise in young female patients and represent 35.6% of all germ cell tumours in this patient group. Teratomas develop outside of the gonads in 1–2% of cases. Extragonadal germ cell tumours, of which teratomas are the most common, typically affect midline structures along the germ cell migration route and arise most commonly in the mediastinum and central nervous system (Wang C, Du J, Xiang X et al. 46, XX disorder of sexual development associated with mixed germ cell tumor of the prostate: a rare case report. BMC Urol 2024; 24: 36). Islands of poorly differentiated, immature, blast-like cells are seen on histology of immature teratomas. They are graded according to the amount of immature neural tissue present and this provides an indication of prognosis.