A Case Report of Tracheal Duplication Cyst with Steatocystomatous histology: A Rare Embryological Overlap

Background: Tracheal duplication cysts (TDCs) are rare congenital anomalies caused by defects in the duplication of the foregut, that is of endodermal origin. These cysts are usually present during childhood and cases in adults are seen very rarely. Steatocystoma multiplex is a disorder of multiple sebaceous cysts, most commonly from skin appendages, that has ectodermal origin. The presence of the two coexisting in the same place has never been reported in literature. We report the first case of a unique embryological overlap between ectoderm and endoderm in a TDC. Case presentation: A 34-year-old Indian male presented with progressive hoarseness and a change in voice. Laryngoscopy revealed left vocal cord paralysis. MRI of the neck done later showed a 3 cm cystic mass in the left tracheoesophageal groove, which was compressing the left recurrent laryngeal nerve. It was surgically excised, and the histopathology revealed a cyst lined by cuboidal epithelium with numerous sebaceous gland nests consistent with steatocystoma multiplex. These findings confirmed a tracheal duplication cyst with unique ectodermal differentiation in this patient. Discussion: Our case stands out for its first-of-its-kind embryological overlap and also for its surgical management. The lack of respiratory epithelium and the presence of sebaceous glands (ectodermal) within a TDC (endodermal) suggest a misdirected embryologic development of the foregut. Dermoid, teratoma, branchial cleft cysts, laryngeal cysts, and malignancy were ruled out. Even though these cysts are benign, they may cause airway obstruction, vocal cord palsy, or other associated compressive symptoms. The treatment of choice for these cysts is en bloc removal, because incomplete excision has been reported to have increased recurrence. Although malignant transformation is rare, histopathological examination is required to rule it out. Conclusion: This is the first reported case of a tracheal duplication cyst with steatocystoma-like histology. It identified the need to consider rare embryologic overlaps while evaluating neck cysts and highlights the importance of thorough histopathological examination for better diagnosis and management.