Dermatofibrosarcoma protuberans of the hallux

Dermatofibrosarcoma is a rare, slow growing, locally destructive, low grade malignancy that originates in the dermis.[1] This tumor has been reported more than 1,000 times in literature; however, in the authors’ literature search, only three cases were found involving the pedal digits and none involving the hallux. [2,3,4]

Dermatofibrosarcoma is most commonly seen in the second through fifth decades.1 The tumor occurs mostly on the trunk and proximal extremities.[5] This rare malignancy accounts for 0.06% to 0.1% of all neoplasms and 1.17% of all tissue sarcomas.[6,7] Metastasis to distant sites is rare and has been seen in approximately 6% of patients.[2,8,9,10,11]

Clinically, the tumor presents as a multilobulated, protuberant nodule that can enlarge over time and become intimate with the skin.[7] The lesion has a keloid type of appearance and can have a blue, red, tan, or purple hue to it. Typically, patients live with this lesion and it remains asymptomatic. Occasionally, the lesion may become complicated by bleeding, pain, infection, or significant enlargement.[2]

The most common differential diagnoses include the following: histiocytoma, localized scleroderma, keloid, fibromatosis, fibrosarcoma, Kaposi’s sarcoma, malignant melanoma, leiomyosarcoma, schwannoma, neurofibroma, and neurofibrosarcoma. Early diagnosis by biopsy is of utmost importance in prevention of progression and metastasis. Histologically, the tumor consists predominantly of uniform cells with large, spindle-shaped nuclei, arranged as irregular, intertwining bands resulting in a storiform appearance. This gives dermatofibrosarcoma protuberans its classic diagnostic “cartwheeling” appearance (Fig. 1).[10] The cells are highly pleomorphic with a high nucleus to cytoplasm ratio with prominent nucleoli that is classic for malignancy.

Dermatofibrosarcoma protuberans is an easily managed neoplastic entity, once the correct diagnosis is made. The treatment of choice is wide and deep excision of the tumor with preferable safety margins being at least 2.5 cm from the periphery of the tumor. This surgical approach is the best means of decreasing the rate of recurrence.[11,12,13,14] Adjunctive radiation therapy has not proven to significantly enhance the cure rate of dermatofibrosarcoma protuberans nor has chemotherapy proven effective. Recurrence rates have been reported to range from 20% to 55% and there is no relationship between the size of the tumor and recurrence.[15,16,17] Following surgical excision, extended follow-up examinations allow for the best clinical outcome for the patient.

Case Report

A 91-year-old male presented with a chief complaint of an enlarged mass on the distal aspect of his left great toe. The mass had been present for more than 30 years and had been asymptomatic until 1 year ago. Within the past year, the patient had begun experiencing pain and discomfort and was unable to wear shoes and walk. His past medical history was significant for chronic atrial fibrillation, colon cancer treated with resection, and right hip fracture treated with open reduction internal fixation. The patient’s medications included digoxin 0.25 mg, four times daily, and with no known drug allergies.

Figure 1. Histologic presentation with cartwheeling.

Figure 1. Histologic presentation with cartwheeling.

The patient was in remarkably good health with no other medical issues. Lower extremity vascular examination revealed bilateral +2/4 dorsalis pedis and posterior tibial pulses and immediate capillary filling time. The neurologic examination revealed intact sharp, dull, and vibratory sensations with +2/4 deep tendon reflex symmetrically. Extrinsic muscle strength was +5/5 of the anterior, lateral, and posterior compartments, bilateral and symmetrically. The dermatologic examination revealed a multilobular, nodular, firm lesion with areas of tan and bluish discoloration on the distal aspect of the left hallux. The lesion measured 5.5 × 5.0 cm (Fig. 2). There were no palpable inguinal or popliteal lymph nodes.

Radiographically, the lesion appeared as a soft tissue mass at the distal aspect of the left hallux. There was no evidence of calcification within the soft tissue; however, cystic changes were noted to be present within the proximal aspect of the distal phalanx of the left hallux. No cortical disruption of the distal phalanx was noted radiographically (Fig. 3).

The patient subsequently underwent an excisional biopsy (distal Syme’s amputation) of the lesion. He recovered uneventfully, with no complications, and returned to his normal activity levels in his usual shoes.

The pathology report revealed spindle-shaped cells with pleomorphism and a high nucleus to cytoplasm ratio. There was evidence of storiform pattern (cartwheeling) of the spindle cells (Fig. 1). The tumor was noted to invade the deep soft tissue and the central aspect of the distal phalanx (Fig. 4).

Figure 2. Left hallux showing lesion measuring 5.5 × 5.0 cm

Figure 2. Left hallux showing lesion measuring 5.5 × 5.0 cm

Figure 3. Radiograph of left hallux with no cortical disruption.

Figure 3. Radiograph of left hallux with no cortical disruption.

Figure 4. Tumorous invasion of bone.

Figure 4. Tumorous invasion of bone.

Conclusion

The authors present a unique case of dermatofibrosarcoma protuberans involving the hallux with invasion of the bone of the distal phalanx. This rare malignancy has infrequently been reported in the pedal digits, with no known cases of the hallux. This case also reveals the extent of local aggression of this tumor with bony invasion, which is a rare occurrence with dermatofibrosarcoma protuberans. A clinician should include dermatofibrosarcoma protuberans in a differential diagnosis of any soft tissue tumor in the foot, and once diagnosed as such, he or she must treat it aggressively with wide margin excision.