Key Pearls On Diagnosing And Addressing Leiomyoma Of The Foot

Emphasizing the importance of early diagnosis, this author presents a guide to the treatment of the rare leiomyoma tumor in two patients.

Leiomyomas are benign soft tissue tumors that arise from smooth muscle. They represent 4.4 percent of all benign soft tissue neoplasms. While leiomyomas are commonly present along the uterus, they rarely occur in the lower extremities. However, clinicians may locate these lesions in any location in which smooth muscle is present, such as the arrector pili muscles, dermal blood vessel walls, scrotum, vulva, nipple and areola.¹

Authors have suggested several classifications of leiomyomas. One classification system describes three types of leiomyomas based on origin: piloleiomyoma, arising from the arrector pili muscles; angioleiomyoma, arising from tunica media found in blood vessel walls; and genital leiomyomas arising from the smooth muscles of scrotum, vulva, nipple and areola.^1-7 Another system classifies leiomyomas into three types: superficial, including cutaneous lesions, angioleiomyomas and leiomyomas of deep soft tissue. Leiomyomas of the extremity are classified as superficial or deep, and can be vascular or non-vascular.

Most leiomyomas are acquired, although researchers have proposed familial inheritance patterns. The most commonly reported types of leiomyomas in the extremities are cutaneous leiomyomas and angioleiomyomas. While leiomyomas of deep soft tissue are rarely discussed in the literature, they have most commonly been described in the lower extremity.^6-7 The medical community has previously questioned the existence of deep soft tissue leiomyomas but the use of well-defined histological criteria has proven their existence.⁸ Deep soft tissue leiomyomas reportedly occur between ages 5 to 65 and are more common in males.⁹ Affected individuals with these lesions in the feet usually present with pain and tenderness associated with shoe gear or ambulation.⁹

Leiomyomas grow slowly and are therefore less symptomatic, tending to present later in life in comparison to cutaneous leiomyomas. Furthermore, these lesions are rarely diagnosed before surgery as imaging modalities, such as magnetic resonance imaging (MRI) and computed tomography (CT) scans, are not specific for diagnosis. Imaging may, however, help in identifying the extent of the lesion and aid with surgical planning. These lesions are usually isointense to muscle on T1 imaging studies and may be heterogeneous on T2 imaging if dystrophic calcifications are present within the lesion. On T2 images, one may appreciate serpiginous hyperintense areas consistent with vascular channels. Physicians have also reported scattered calcification when describing deep soft tissue leiomyomas on imaging, a finding that could lead to clinical misdiagnosis.¹⁰ The differential diagnosis for leiomyoma includes, but is not limited to, neurofibroma, lipoma, schwanomma, hemangioma and soft tissue giant cell tumor of the tendon sheath.

On gross examination, deep soft tissue leiomyomas are typically round, beige, and encapsulated with a shiny appearance. Calcifications may be present within the tumor and often represent degeneration of the tumor. Calcifications more frequently occur with leiomyomas of deep soft tissues than any other type of leiomyoma. Authors have described different patterns and the pathophysiology associated with these calcifications is unknown.^11-13 

Microscopically, leiomyomas lack mitotic activity and are usually composed of fascicles of smooth muscle cells with elongated and blunt-ended nuclei and ample eosinophilic cytoplasm. Calcifications may be large, small or psammoma-like bodies. On an immunohistochemical exam, leiomyomas are positive for smooth muscle actin and caldesmon, and negative for S100 protein, findings that are important for diagnosis.^9,13

The treatment of choice for leiomyoma of deep soft tissue is surgical excision, which allows for a definitive diagnosis. One must take care to ligate or cauterize all vessels associated with the mass. Although recurrence and malignant transformation of leiomyomas are rare, a careful treatment approach is recommended with histopathologic testing to rule out necrosis, nuclear atypia and mitotic activity.¹⁴

Here are two cases of patients who presented with leiomyoma of the foot.

Case Study One: When There Is A Draining Wound Due To Deep Soft Tissue Leiomyoma

A 65-year-old male presented to the emergency department with a new, painful, draining first metatarsophalangeal joint (MPJ) wound. He reported a growing mass and worsening pain over the past 15 years under the first metatarsal near the site of the ulceration. He also complained of episodic pain throughout the years, which became worse with ambulation and shoe gear. The patient related no fevers, lymphadenopathy, weakness or unintentional weight loss.

The initial physical examination revealed a 3 cm palpable mass with an overlying ulceration medially that probed approximately 1 cm but did not probe to bone. Radiographs of the left foot revealed several amorphous areas of soft tissue calcification adjacent to the plantar aspects of the heads of the first and second metatarsals. The cortex of the first metatarsal and proximal phalanx remained intact. A MRI of the left foot revealed a complex 40 mm lesion along the plantar and medial aspect of the left forefoot in contiguity with the plantar aspect of the flexor hallucis longus tendon subjacent to the first MPJ. The lesion contained mixed elements that represented calcifications evident on all views. The hyperintense areas formed a sinus tract that extended medially and communicated with the wound. Differential diagnosis for this patient included lipoma, fibroma, hemangioma, gouty tophi and rheumatoid nodule.

The wound cultures of the left foot revealed Stenotrophomonas maltophilia, an aerobic Gram-negative bacillus. Initial treatment consisted of local wound care and oral antibiotics. During subsequent visits, a minimal amount of purulence drained from the medial ulceration site along with chalky white material, and a second medial ulceration developed.

Given the non-healing progression of the wound, I performed surgical excision of the left foot soft tissue mass. I excised the mass and wounds from within the subcutaneous tissue through a plantar 4 cm curvilinear incision along the first submetatarsal area. The mass was firm, tan, round and encapsulated, measuring 3.5 x 2.8 x 1.7 cm. No blood vessels were noted extending into the lesions macroscopically during excision. No deep extension into the long flexor tendon or osseous structures was present.

I excised a sinus tract medial to the site of the mass and sent it separately for pathology. I took pre- and post-lavage cultures and sent them for analysis. The cultures revealed coagulase-negative staphylococci and Candida albicans.

Layered closure of the deep and superficial soft tissues occurred without complications. Postoperatively, the patient bore weight as tolerated in a surgical shoe. His incision healed without complications and he reported significant pain-relief following excision of the mass. No recurrence of the mass, wound or infection has occurred to date. 

Histopathological analysis showed bland spindle cells positive for vimentin and desmin, and negative for S100 and CD34. The findings confirmed the diagnosis of leiomyoma with calcifications. No vascular channels were present within the specimens I examined microscopically.

Case Study Two: Treating Degenerative Leiomyoma With Dystrophic Calcification

A 66-year-old female patient presented for an evaluation of a painful cyst on the dorsum of the right second toe, which she related had been present for 15 years. She denied any history of trauma to the affected area and reported no recent growth in the mass. She related pain and irritation over the affected area with direct palpation and shoe gear. No prior treatment or imaging of the soft tissue lesion were reported by the patient. The patient’s past medical history was significant for hypertension and type 2 diabetes mellitus. The patient denied any nausea, fevers, chills, chest pain, shortness of breath, lymphadenopathy, weakness, and or recent unintentional weight loss.

On physical examination, a palpable, non-mobile, soft tissue mass was present on the dorsal aspect of the right second toe measuring approximately 1.7 cm x 1.7 cm. There was no evidence of erythema, fluctuance or crepitus. No open skin lesion was present. The rest of the patient’s physical exam was unremarkable. Radiographic imaging of right foot revealed multiple localized areas of soft tissue calcification within the area of the soft tissue lesion. No evidence of fracture or dislocation was present. I discussed conservative and surgical treatment options with the patient. She elected to have surgical removal of the soft tissue mass in the right second toe.

The surgical procedure consisted of a dorsal elliptical incision from the level of the right second proximal interphalangeal joint to the proximal nail fold. I easily identified, freed and excised the soft tissue mass. Closer inspection revealed a clearly defined gray and tan-colored, well encapsulated soft tissue mass measuring 1.0cm x 1.0cm x 0.8cm with no associated vasculature infiltration, tendinous or osseous attachment. I sent the soft tissue mass to pathology for assessment.

The final diagnosis of the soft tissue mass was degenerative leiomyoma with dystrophic calcification. The patient tolerated the surgical procedure well and postoperatively, she remained pain-free and healed without complication or recurrence.

In Conclusion

Leiomyomas in the foot are rare entities. When they manifest in the foot, early diagnosis can prove to be challenging initially, thereby increasing the risk of misdiagnosis and delayed treatment. Surgical excision is necessary for definitive diagnosis and treatment. Imaging modalities, although not specific for diagnosis, can aid in surgical planning.

Our first case shows an unprecedented initial presentation of a painful, draining infected wound due to an underlying deep soft tissue leiomyoma while the second case shows a more typical presentation of leiomyoma in a digit. Together, the cases highlight the importance of a wide differential diagnosis, especially in the face of an atypical soft tissue mass presentation.

Dr. Cornell is a Diplomate of the American Board of Foot and Ankle Surgery. She is fellowship trained in diabetic limb salvage and currently in private practice in Havertown, Pa. She is an attending physician with the Crozer-Keystone Health System Podiatric Residency program.

Dr. Patel is a third-year Chief Resident within the Department of Foot and Ankle Surgery at Crozer Keystone Health System in Upland, Pa.

Dr. Guillen is a second-year resident within the Department of Foot and Ankle Surgery at Crozer Keystone Health System in Upland, Pa. 

References

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