DISTAL PHALANGEAL EROSIVE LESIONS

Transcription

1 449 RADIOLOGIC VIGNETTE DISTAL PHALANGEAL EROSIVE LESIONS BAKBARA MONSEES and WILLIAM A. MURPHY Many lcsions occur in the distal phalanges of the hand. These may cause pain and mistakenly be attributed to a manifestation of a more generalized arthropathy. While gout and rheumatoid arthritis cause distal phalangcal erosions, other soft tissue and bone lesions do also. Benign and malignant soft tissue and bone neoplasms, as wcll as infection and systemic diseases, will be considered here (Table 1). Acroosteolysis has recently been reviewed and will not be further described (1). The purpose of this vignctte is to discuss these various erosive lesions, their typical clinical presentation, and those radiologic features that help differentiate them. Benign diseases: soft tissue lesions Epidermoid inclusion cyst. Thc cpidermoid inclusion cyst is synonymous with a keratin, scbaceous. epithelial, squamous, or implantation cyst. Pathologically, this is not a true neoplasm. but rather a unilocular cystic cavity consisting of laminatcd masses of keratin with a peripheral zone of squamous epithclium. The origin of the osseous lesion is most likcly trauma (2,3), the probablc mechanism bcing relatcd to thc implantation of epithelial tissue into soft tissue or bone during a crush or penetrating injury. An alternativc ctiologic theory is that of embryologic misplaccment of epidermal cells (43). Clinically, these patients may be totally asymptomatic or may have a history of From the Mallinckrodt Institute of Kadiology. Washington University School of Medicinc, St. Louis. Missouri. Barbara Monsces, MI): William A. Murphy. MD. Address reprint rcquests to William A. Murphy, MD. Mallinckrodt Institute of Kadiology. Washington University School of Medicine, St. Louis, MO Submitted for publication September 23, 1983; accepted September intermittcnt pain. On physical examination they may exhibit tenderness, curving of the overlying nail, and pseudoclubbing of the fingertip. Occasionally, they may prcsent with pain from a pathologic fracture or from a secondary infection of the lesion. A clearcut history of trauma may not exist and it may have taken many years for the lesion to develop and become symptomatic. The age of prescntation is variable, with a pcak incidence in the fourth decade (5). On radiographic cxamination, the epidermoid inclusion cyst is characterized by a well-defined cystic lucency in the distal phalanx. It may be expansile, frequently have a sclerotic rim, lack calcification, and occur more commonly in the phalangeal tuft, rather than at its base (Figure 1). Glomus tumor. The glomus body is an endorgan apparatus. an arteriovenous anastomosis without an intermediary capillary bed. Located in the soft tissucs beneath the fingernails and on the ventral surface of the fingertips, its function is to aid in the regulation of circulation and temperature control. The glomus tumor, a hamartoma of hypertrophied clcrnents of the normal glomus body, is usually a wcllencapsulated, soft, pink or purple mass, smaller than I crn in diameter. In the series of 28 glamus tumors reported by Carroll and Berman (6). 14 wcrc located in the subungual region, 11 were located in the palmar lateral aspect of the distal phalanx, and 3 were locatcd in the palm. The average age of the patients was 40, and they frequently had symptoms long before diagnosis (7). Clinically, thcsc patients complain of paroxysmal lancinating pain and cold scnsitivity. On examination, many of these tumors appear as a blue spot in the subungual region which, when palpated, is very tendcr. Occasionally, the overlying nail is ridged. Arthritis and Rheumatism, Vol. 27, No. 4 (April 1984)

2 MONSEES AND MURPHY Table 1. Diseases causing erosions of the distal phalanx Benign diseases Soft tissue lesions Epidermoid inclusion cyst Glomus t umor Keratoacanthoma Osseous neoplasms Enchondroma Osteoid osteoma Other neoplasms Malignancies Primary epidermoid carcinoma Malignant osseous neoplasms Metastases Infection Manifestation of systemic disease Because this is a soft tissue tumor which arises extrinsic to bone, these patients may have no radiologic findings (6). When there is osseous involvement, it is characteristically an extrinsic pressure erosion, although occasionally, a more punched out appearance develops. Such a lesion has a well-defined, sometimes sclerotic margin and lacks pcriosteal rcaction or calcification of the tumor matrix (Figure 2). Keratoacanthoma. The keratoacanthoma, an uncommon tumor, is a nodule of well-differentiated Figure 2. Glomus tumor. Well-defined pressure erosion along the dorsal aspect of the distal phalanx underlying the nail bed. (The view is slightly oblique.) squamous epithelium that is locally invasive. It is initially manifested by pain, swelling, and inflammation, and has a short history of only weeks or a few months duration. Presence of a tumor mass is fairly common (8). Bone destruction of the distal phalanx is present in virtually all cases of subungual keratoacanthoma and may be seen on radiographs even when examined shortly after clinical prescntation. The destruction is characteristically well-defined, smooth, and circular, and limited to the tip of the phalanx (Figure 3). The bony erosion is generally attributed to pressure from the rapid growth of the adjacent neoplasm. Following excision of the tumor, the phalangeal tuft erosion may repair. Figure 1. Epidermoid inclusion cyst. Well-defined cystic lesion with sclerotic rim in the tuft and a pathologic fracture. Benign diseases: osseous neoplasms Enchondroma. The enchondroma, a benign tumor arising from mature hyaline cartilage, is the most common primary tumor of the tubular bones of the hands and feet. It may occur in monostotic or polyostotic forms, and is most commonly found in the proximal phalanges, but may occur in any of the metacarpals, phalanges, or carpal bones. Only a small

3 RADIOLOGIC VIGNETTE 45 1 connective tissue. It may arise in medullary, cortical, or subperiosteal locations and the site of origin usually dictates a characteristic radiologic appearance. Clinically, osteoid osteoma occurs in patients approximately 20 years of age, who complain of progressive aching pain. On physical examination, they frequently have an enlarged fingertip with hypertrophy of the nail, hyperhydrosis, and pain on direct palpation. Young patients may have premature fusion of the adjacent epiphysis, perhaps relating to increased blod flow (13). Radiologically, the appearance of an osteoid osteoma depends on its site of origin. Purely intramedullary tumors frequently incite little reactive bone, while cortically-based lesions cause intense bone formation. Subperiosteal lesions elevate the periosteum and incite periosteal reaction. Aulicino et al (I I) reviewed the reported cases of osteoid osteoma in the terminal phalanx and concluded that all the lesions in this area had a similar appearance characterized by a Figure 3. Keratoacanthoma. Fairly well-defined, crescent-shaped erosive lesion of tuft adjacent to the overlying nail bed. percentage occur in the distal phalanges (9,lO). Clinically, patients with an enchondroma may be asymptomatic and the lesion discovered incidentally, or they may present with pain and a pathologic fracture. Radiologically, this lesion may be impossible to differentiate from other lesions, such as an cpidermoid inclusion cyst, especially when the erosion is small. Characteristically, an enchondroma is a small, welldefined cystic lucency in the phalanx, sometimes having scalloped margins or a sclerotic rim, and is most commonly located centrally in the bone. Features that differentiate an enchondroma from an epidermoid inclusion cyst may include expansion of the cortex, presence of bony septae, and calcification within the matrix. In the distal phalanx, the enchondroma is typically located at the base of the phalanx, abutting the articular surface (Figure 4). Osteoid osteoma. Osteoid osteoma has been reported in virtually all bones of the body with the exception of the skull, but its occurrence in the hand is uncommon, especially in the terminal phalanx (11-13). It is a benign osteoblastic lesion consisting of a small oval or round mass, called a nidus. which is usually smaller than 1 cm. Histologically, the nidus is a lln2hvork of osteoid ~ ~~b~culae with varying degrees of mineralization in a background of vascular fibrous Figure 4. Enchondroma. Slightly expansile cystic lesion at base of distal phalanx.

4 452 MONSEES AND MURPHY sclerotic nidus with a radiolucent halo, or the so-called ring sequestrum (12). Other benign neoplasms. Aneurysmal bone cysts (9,14) and giant cell tumors (15) may rarely occur in the distal phalanges. They may both have a history of rapid growth, pain, and swelling. Both may have similar radiologic features characterized by lytic, cxpansile lesions involving the entire phalanx. The cortex may be interrupted, simulating a malignant tumor. Hemangiomas of the hand may arise in the bone or soft tissue. When primary in bone, they have a characteristic radiographic appearance of linear striations parallel to the shaft of the bone (16). Soft tissue hemangiomas are more common lesions and may be radiographically manifested by local soft tissue masses, localized bony overgrowth, phleboliths in the soft tissue, and pressure erosion of the underlying bone (Figure 5). Malignancies Primary epidermoid carcinoma. Subungual epidermoid carcinoma is uncommon and is manifested by pain, swelling, and inflammation. The symptoms are usually of long duration-many months to years. Generally, an obvious tumor mass is not found, although Figure 5. Hemangioma. Well-defined, eccentric, scooped out pressure erosion adjacent to a soft tissue mass. The clue to the diagnosis in this patient is the phlebolith in the proximal soft tissue (arrow). Figure6. Chondrosarcoma. Expansile lytic erosion at the base of the distal phalanx with cortical disruption (arrows) and an associated soft tissue mass. inflammation is present. Chronic infection may complicate or initiate the cancer (17). Carcinoma of the nail bed has radiologic findings in approximately 60% of cases (8). The bone erosion is variable, from irregular destruction to a smooth pressure erosion. Malignant osseous neoplasms. Malignant tumors of the hand are usually of soft tissue origin, predominantly of the skin (18). Malignant tumors of osscous origin rarely occur in the digits of the extremities. Chondrosarcoma (19,20), osteosarcoma, fibrosarcoma, synovial sarcoma (21), and Ewing s sarcoma (22) have all been reported, but chondrosarcoma is by far the most common. These are usually aggressive lesions often manifested by cortical destruction and extension of the tumor into the soft tissue. Patients often have pain and soft tissue swelling and the clinical picture may simulate infection (2 1). Chondrosarcoma may arise in a preexisting enchondroma (18) (Figure 6). Metastatic tumor. Metastases to the peripheral bones of the hands and feet are uncommon because most bone metastases occur in hematopoietically active bones, such as those of the central skeleton. Bronchogcnic carcinoma and, to a lesser extent, sev-

5 RADIOLOGIC VIGNETTE 453 Figure 7. Metastatic epidermoid carcinoma. Near total destruction of the distal phalanx with a large associated soft tissue mass. The articular cortex at the phalangeal base is preserved. A era1 other primary malignancies are known to cause peripheral bone metastases. The probable mechanism involves erosion of the pulmonary veins by tumor, giving tumor emboli access to the systemic arterial circulation (23,24). Clinically, these patients present with a swollen, erythematous, painful, and warm digit-the picture of an acute inflammatory condition. Most of the time they have a known malignancy, usually carcinoma of the lung, but occasionally they may have no history of malignancy and seek medical attention only for their symptomatic digit (25,26). Appearance on radiograph differs dramatically from that of the benign cystic and pseudocystic erosions described above, but is difficult to distinguish from osteomyelitis. Metastases are more destructive, often have a large associated soft tissue mass, and are usually osteolytic without reactive bone or periosteal reaction. The bone erosion is usually fairly welldefined with preservation of the bone mineral around the site of destruction. Distal phalangeal metastases usually do not cross the articular surface. In fact, they preserve a thin margin Of dral cortical bone and sometimes, a blown-out cortical shell (Figure 7). B Figure 8. Osteomyelitis secondary to a felon. Permeative destructive lesion with fragmentation of the bony tuft, Soft tissue predominantly of the pulp space reflects the site of origin of this infection. Anleroposterior (A) and lateral (B) views.

6 454 MONSEES AND MURPHY Figure 9. Tuberous sclerosis. Numerous cystic lesions in the distal and middle phalanges. The multiplicity of lesions, their eccentric location, and accompanying sclerosis aid in the diagnosis. Infection Osteomyelitis of the distal phalanx usually occurs following local injury or soft tissue infection rather than by the hematogenous route. Lacerations, compound fractures, puncture wounds, burns, and bites are common predisposing factors (16). Primary and metastatic tumors can mimic an inflammatory lesion, and infection can complicate underlying primary lesions. Clinically and radiographically, osteomyelitis in the digit is similar to infection elsewhere in the body. Soft tissue swelling, focal osteopenia, periosteal reaction, bone destruction, and sequestrum formation may all be present (Figure 8). Manifestation of systemic disease Certain systemic diseases such as scleroderma have findings referable to the distal phalanges. These are not usually diagnostic problems because the underlying diagnosis is known. However sarcoidosis, for example, may present with finger pain as the initial symptom of the disease (27). When radiographs are carefully evaluated, sarcoid usually exhibits a multiplicity of findings. The clinical distribution of disease may also give a clue to the correct diagnosis. Tuberous sclerosis may exhibit cystic foci in the phalanges (Figure 9). The multiplicity of lesions, accompanied by adjacent areas of sclerosis, is characteristic of this syndrome (28). The appropriate diagnosis in these patients is usually clinically evident. Conclusion There are several common lesions that can cause pain and erosion of the distal phalanx. These include epidermoid inclusion cyst, enchondrorna, glomus tumor, and infection. Other lesions less commonly found in this location have also been discussed. The patient s symptoms, physical, and radiographic findings may help to limit the differential diagnosis and exclude a systemic arthropathy. In many cases, although a best diagnosis may be offered, a biopsy may be necessary to make the correct diagnosis.

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