Primary immature teratoma of the thigh

Abstract

Teratomas are germ cell tumours composed of a variety of somatic tissues derived from more than one germ layer (ectoderm, endoderm and mesoderm), commonly found in the gonads, in children and young adults.1Kurman R.J. Carcangiu M.L. Herrington C.S. WHO Classification of Tumours of Female Reproductive Organs. 4th ed. IARC Press, Lyon2014Google Scholar Less frequently teratomas arise in extragonadal sites, usually in a midline location, such as sacrococcygeal region, retroperitoneum, mediastinum and central nervous system. Mature teratomas harbour, by definition, mature, benign, well-differentiated tissues, while immature teratomas are composed of variable amounts of fetal, immature tissues. Monodermal teratomas are defined by the presence of a single tissue type (i.e., thyroid tissue in struma ovarii). Usually, immature teratomas are graded according to the Norris grading system,2Norris H.J. Zirkin H.J. Benson W.L. Immature (malignant) teratoma of the ovary: a clinical and pathologic study of 58 cases.Cancer. 1976; 37: 2359-2372Crossref PubMed Scopus (545) Google Scholar based on the presence and amount of immature neuroepithelial component. Both mature and immature teratomas may contain foci of other germ cell tumours, as well as foci of malignant transformation. We report the very unusual case of a primary immature teratoma arising in left thigh soft tissue in an elderly woman. An 86-year-old female presented with an ulcerated soft tissue mass in the postero-inferior region of the left thigh. The resected lesion, measuring 14 × 13 × 4.5 cm, appeared soft, brownish and multilobulated on the surface. After sectioning, the mass showed both solid and cystic-like areas containing a mucoid material; necrosis and haemorrhages were also present. Histological examination revealed a neoplasm with both mesenchymal and epithelial differentiation. Areas with tubular and glandular structures, reminiscent of embryonic tissues, embedded in a cellular stroma, were frequently observed (Fig. 1A,B). Cystic spaces lined by a prismatic or cubic epithelium were also present. Primitive MAP2+/CD56+ neuroepithelium arranged in tubules and rosettes, with brisk mitotic activity, admixed with mature glial (GFAP+) and meningeal tissue, was frequently detected (Fig. 1C). A scarce mesenchymal component was also present, prevalently consisting of mature cartilage islands (Fig. 1D) and well differentiated smooth muscle fibres, without overt features of malignancy. Infiltration of soft tissues at the periphery of the lesion was focally observed. In the specimens examined, there was no evidence of residual ovarian tissue. The above morphological features led to a diagnosis of immature teratoma (grade 3, according to Norris et al.).2Norris H.J. Zirkin H.J. Benson W.L. Immature (malignant) teratoma of the ovary: a clinical and pathologic study of 58 cases.Cancer. 1976; 37: 2359-2372Crossref PubMed Scopus (545) Google Scholar Based on the absence of clinical and radiological evidence of an ovarian lesion or tumour mass elsewhere, the teratomatous lesion of the thigh was assumed originating primarily in soft tissues. Serological levels of AFP and CA19.9 were not evaluated in the postoperative course. After surgery, the patient was lost to follow-up. The occurrence of a teratoma outside the common gonadal and midline locations is exceedingly rare. Interestingly, in female patients we did not find reports on primary immature teratoma located in soft tissues of the extremities, but only two cases of thigh metastasis from ovarian teratoma.3Plaza J.A. Perez-Montiel D. Mayerson J. et al.Metastases to soft tissue: a review of 118 cases over a 30-year period.Cancer. 2008; 112: 193-2013Crossref PubMed Scopus (138) Google Scholar,4Byun J.C. Choi I.J. Han M.S. et al.Soft tissue metastasis of an immature teratoma of the ovary.J Obstet Gynaecol Res. 2011; 37: 1689-1693Crossref PubMed Google Scholar Ovarian immature teratoma commonly metastasises to the peritoneal cavity or regional lymph nodes and, less frequently, to lung and liver. In male patients, only three cases of primary teratoma located in soft tissue of the extremities have been reported, in the absence of clinically appreciable testicular or lesions elsewhere.5Chinoy R.F. Soman C.S. Swaroop D. et al.Extragonadal malignant teratoma of the foot.Indian J Cancer. 1992; 29: 96-99PubMed Google Scholar, 6Benali A.H. Lalya L. Allaoui M. et al.Extragonadal mixed germ cell tumor of the right arm: description of the first case in the literature.World J Surg Oncol. 2012; 10: 69Crossref PubMed Scopus (11) Google Scholar, 7Zuquello R.Á. Tagliari G. Bagatini R. et al.Immature teratoma presenting as a soft-tissue mass with no evidence of other sites of involvement: a case report.Diagn Pathol. 2016; 11: 76Crossref PubMed Scopus (3) Google Scholar Notwithstanding, cases of soft tissue metastases from testicular germ cell tumours have been documented.8Bilici A. Ustaalioglu B.B. Seker M. et al.Case report: soft tissue metastasis from immature teratoma of the testis: second case report and review of the literature.Clin Orthop Relat Res. 2010; 468: 2541-2544Crossref PubMed Scopus (9) Google Scholar In the present case, the occurrence of an immature teratoma located in soft tissues of the thigh in an elderly female patient, in the absence of clinical and radiological evidence of ovarian or tumours elsewhere, strongly favours a primary origin of the lesion. Our assumption seems supported by the common knowledge that ovarian immature teratomas occur during the first decades of life, as confirmed by Norris et al., who did not find any such tumour in female patients older than 40 years.1Kurman R.J. Carcangiu M.L. Herrington C.S. WHO Classification of Tumours of Female Reproductive Organs. 4th ed. IARC Press, Lyon2014Google Scholar,2Norris H.J. Zirkin H.J. Benson W.L. Immature (malignant) teratoma of the ovary: a clinical and pathologic study of 58 cases.Cancer. 1976; 37: 2359-2372Crossref PubMed Scopus (545) Google Scholar