The majority of cysts that develop in the hand affect the metacarpals and phalanges. Due to the rarity of these lesions, aneurysmal bone cysts are often misdiagnosed as more common tumors such as giant cell tumors, benign cartilage tumors, or interosseous ganglion (Mankin et al. 1995). Progression of aneurysmal bone cysts has been described in four phases. The initial phase is characterized by osteolysis of the marginal aspect of the bone with periosteal elevation. The growth phase is indicated by progressive destruction of the bone leading to poor demarcation of the lesion. The stabilization phase is identified by the classic appearance of the cyst with a well-defined bony shell and osseous septations. Lastly, the healing phase is observed when advancing ossification of the lesion is apparent (Dabaska and Buraczewski 1969; Rapp et al. 2012).

Initially, ABCs were thought to develop in response to an intraosseous hemorrhage, leading to formation of a cyst (Lichtenstein 1950; Ratcliffe and Grimer 1993). However, recent genetic and histopathologic studies have suggested that aneurysmal bone cysts are likely to represent true neoplasms undergoing tumorigenesis rather than reactive lesions (Oliveira et al. 2004; Ye et al. 2010; Fig. 1).

Bizarre parosteal osteochondromatous proliferation (BPOP, Nora’s lesion) is a benign, reactive proliferation of bone and cartilage that is often associated with a traumatic injury to the hand (Orui et al. 2002; Payne and Merrell 2010). These lesions arise from cortical bone and are not continuous with the medullary cavity. Plain radiographs typically demonstrate a well-defined calcified mass arising from the surface of the bone (Michelsen et al. 2004; Orui et al. 2002). Histology demonstrates a lesion with a cartilage cap comprised of bizarre-appearing chondrocytes and hypercellularity (Payne and Merrell 2010). Due to the aggressive appearance on radiographs and histology, BPOP may initially be mistaken for a parosteal osteogenic sarcoma. Surgical excision is the treatment of choice for these lesions despite the high risk for local recurrence. In order to decrease the risk of recurrence, Michelsen et al. have suggested excising the underlying periosteum as well (Michelsen et al. 2004). Wide or radical excision is generally unwarranted due to the benign clinical course.

Chondromyxoid fibroma is a rare benign cartilaginous tumor that accounts for less than 1 % of all bone tumors. This lesion typically presents in the second or third decade of life, with males affected twice as often as females (Nalbantoglu et al. 2005).

Enchondroma is a benign intramedullary cartilaginous neoplasm. It is the most common primary bone tumor of the hand, accounting for approximately 90 % of bone tumors in the hand. Furthermore, approximately 35 % of all enchondromas develop in the hand (Bauer et al. 1988). Enchondromas typically occur in younger patients with more than 50 % of patients between 11 and 30 years of age (Nurboja et al. 2006).

Giant cell tumor (GCT) of bone is an uncommon tumor that accounts for approximately 5 % of bone tumors (Athanasian et al. 1997). Although classified as benign based on histology, GCTs of bone may be locally aggressive, metastasize, and ultimately be fatal.

Maffucci’s syndrome is a rare, congenital enchondromatosis similar to Ollier’s disease; however, patients with Maffucci’s syndrome additionally exhibit multiple hemangiomas. The hands are affected in the majority of cases of Maffucci’s syndrome. Radiographically, Maffucci’s syndrome appears identical to Ollier’s disease, except for the presence of phleboliths, which correspond to the hemangiomas. Deformity of the hands may occur, and patients with this syndrome are at high risk for the development of both bone and soft tissue sarcomas (Jacobs et al. 2010).

Multiple enchondromatosis (Ollier’s disease) is a rare, nonhereditary condition in which multiple enchondromas occur, predominantly in a unilateral distribution (Fig. 5) (Fang et al. 2009). The disease typically affects the metaphysis and diaphysis of long bones or short tubular bones of the hands and feet (Bükte et al. 2005). Ollier’s disease has an incidence of approximately 1:100,000, with females more commonly affected (Fang et al. 2009; Van Loon and Lammens 2008).

Evidence of Ollier’s disease generally presents prior to puberty, as the lesions become more apparent with progressive skeletal growth (Bükte et al. 2005). Therefore, it is important to note that growth of an enchondroma after skeletal maturity may indicate malignant transformation. Approximately 30 % of patients with Ollier’s disease will develop a malignant bone neoplasm, specifically chondrosarcoma or osteosarcoma. Thus, patients with Ollier’s disease should undergo regularly scheduled serial physical and radiologic examinations. Other sequelae of Ollier’s disease can include skeletal deformities and/or a limb-length discrepancy (Van Loon and Lammens 2008). Progressive nonmalignant deformity can be treated with a diaphysectomy and fibula strut grafting (Fatti and Mosher 1986). Partial resection of the cortical bone with curettage of the tumor (corticoplasty) has also been shown to be successful in treating Ollier’s disease (Kim et al. 2012).

Multiple hereditary exostoses are a rare autosomal dominant condition that has numerous cartilage-capped benign bony lesions, osteochondromas, at areas of active bone growth. The incidence is approximately 1 in 50,000 (Vanhoenacker et al. 2001). The osteochondromas typically affect both the upper and lower extremities (Fig. 6), with the humerus being the most common location in the upper extremity (Shapiro et al. 1979). Complications arising from this disorder include bony and cosmetic deformities; pathological fracture; bursa formation with subsequent pain; impingement of nearby tendons, nerves, and blood vessels; and malignant transformation (Murphey et al. 2000). Malignant transformation has been reported to occur in 3–5 % of patients with multiple hereditary exostoses (Murphey et al. 2000). It is impossible to remove all of the lesions, and therefore, only the symptomatic ones are addressed. Surgical excision is reserved for the lesions that cause growth disruption, pain, or neurovascular injury. Patients may require multiple procedures over the course of their lives to correct limb-length discrepancies or to excise painful lesions (McBride 1988).

Non-ossifying fibroma is a benign fibrous growth resulting from a developmental defect in which fibrous connective tissue fills areas that normally ossify. These lesions develop in childhood and adolescence and generally arise in the metaphysis of long bones (Noh et al. 2013). The incidence of non-ossifying fibroma in skeletally immature children is 30–40 %, with males affected twice as much as females (Hudson et al. 1993; Shimal et al. 2010).

Osteoblastoma is a rare benign bone tumor accounting for approximately 1 % of bone tumors (Cerase and Priolo 1998). These lesions commonly present in the second decade of life and affect males more often than females.