A 30-year-old man has pain in the right wrist after falling on his outstretched right hand. Radiographs of the wrist show normal findings; a radiograph of the hand is shown above. Which of the following is the most likely diagnosis?

(A) Chondromyxoid fibroma
(B) Enchondroma
(C) Giant cell tumor
(D) Osteoid osteoma
(E) Osteosarcoma

The correct response is Option B.

The most likely diagnosis is enchondroma, a benign cartilaginous tumor that is the most common primary tumor of bone in the hand. Enchondromas typically develop during the second or third decade of life. Although they are often asymptomatic and discovered incidentally on imaging studies, as in this patient, pathologic fractures occurring in the
area of the tumor may lead to diagnosis. Pain in the absence of fracture is suggestive of malignant degeneration.
In patients with enchondromas, radiographs show a scalloped, lytic lesion within the medullary canal of the affected bone, occasionally with scattered calcification. Periosteal reaction is rare. Microscopic examination shows benign clusters of hyaline cartilage surrounded by lamellar bone with varying calcification.

Enchondromas that develop on the surface of the bone or within the cortex are known as periosteal or juxtacortical chondromas. Conditions associated with enchondroma include Ollier disease, or multiple enchondromatosis, and Maffucci syndrome, in which patients have multiple enchondromas associated with subcutaneous hemangiomas.
Appropriate management is curettage of the lesion. Bone grafting or use of a bone substitute may be required.

Chondromyxoid fibromas are benign cartilaginous tumors that rarely occur in the upper extremity. Radiographs show a radiolucent lesion with small sclerotic rims that separate the tumor from lamellar bone.

Giant cell tumors of bone are not common in the hand, wrist, or distal forearm. Only 2% to 5% of all giant cell tumors of bone occur in the hand; in contrast, the radius is the third most commonly affected site, with 16% of all giant cell tumors of bone occurring in this region. Management is controversial, as limited resection is associated with high recurrence rates locally, and more aggressive resection is likely to result in significant limitation of function.

Osteoid osteomas are symptomatic lesions. Affected patients have pain, especially at night, that is relieved with administration of nonsteroidal anti-inflammatory agents. Radiographs show a target-like lesion, illustrating the central nidus of the tumor within the bone.

Osteosarcomas are also rare in the hand. These malignant tumors exhibit varying degrees of bone erosion and periosteal reaction.

References
1. Floyd WE 3rd, Troum S. Benign cartilaginous lesions of the upper extremity. Hand Clin. 1995;11:119-32.
2. Putnam MD, Cohen M. Malignant bony tumors of the upper extremity. Hand Clin. 1995;11:265-286.

A 67-year-old man has a mass overlying the metacarpal of the right index finger that has enlarged rapidly over the past six weeks. He underwent kidney transplantation for polycystic renal disease five years ago. Which of the following is the most appropriate management?

(A) Observation for spontaneous involution
(B) Electrodesiccation and curettage
(C) Interlesional injection of 5-fluorouracil
(D) Excisional biopsy and primary wound closure
(E) Excision and sentinel node biopsy

The correct response is Option D.

This 67-year-old man has a keratoacanthoma, a cutaneous lesion that appears similar to squamous cell carcinoma. Although keratoacanthomas had been thought previously to be benign, recent studies have suggested that this lesion
is actually a variant of squamous cell carcinoma. Keratoacanthoma first appears as a red papule on sun-damaged skin and expands rapidly over several weeks. Although most keratoacanthomas regress even without treatment, some can be aggressive and metastasize. Because these lesions have shown an affinity for immunosuppressed patients, an association has been suggested.

Excisional biopsy is most appropriate because the architecture of the lesion is important for accurate diagnosis. In this patient who has a keratoacanthoma affecting the right index finger, the wound can be closed primarily.

Observation for spontaneous involution is obviously inadequate and even dangerous in an immunocompromised patient with a keratoacanthoma because of the risk for aggressive tumor growth and metastasis.

Electrodesiccation and curettage and interlesional injection of 5-fluorouracil are not appropriate therapy in immunocompromised patients.

Sentinel node biopsy is excessive because the risk for lymphatic spread is low.

References
1. Magee KL, Rapini RP, Duvic M, et al. Human papilloma virus associated with keratoacanthoma. Arch Dermatol. 1989;125:1587-1589.
2. Sanders GH, Miller TA. Are keratoacanthomas really squamous cell carcinomas? Ann Plast Surg. 1982;9:307-309.