Obermeier mentions several cases.

Gibson and Malet describe a presternal fissure uncovering the base of the heart.

Ziemssen, Wrany, and Williams also record congenital fissures of the sternum.
Thomson has collected 86 cases of thoracic defects and summarizes his paper by saying that the structures deficient are generally the hair in the mammary and axillary regions, the subcutaneous fat over the muscles, nipples, and breasts, the pectorals and adjacent muscles, the costal cartilages and anterior ends of ribs, the hand and forearm; he also adds that there may be a hernia of the lung, not hereditary, but probably due to the pressure of the arm against the chest.

De Marque gives a curious instance in which the chin and chest were congenitally fastened together.

Muirhead cites an instance in which a firm, broad strip of cartilage resembling sternomastoid extended from below the left ear to the left upper corner of the sternum, being entirely separate from the jaw.
Some preliminary knowledge of embryology is essential to understand the formation of branchial fissures, and we refer the reader to any of the standard works on embryology for this information.