A Prepatellar Soft Tissue Mass in a 56-Year-Old Man (2003)

A 56-year-old man presented with an enlarging painless mass in the soft tissue around his right knee. The patient initially noticed the lesion 2 to 3 years before presentation. It began as a small nodule in the soft tissue anterior to the patella. The patient denied any antecedent trauma. He had no activity-related pain, nocturnal pain, weight loss, or any restriction of motion. His medical history was significant for insulin-dependent diabetes mellitus, hypertension, and coronary artery disease. His surgical history was remarkable for a kidney transplant in 1995 and a coronary artery bypass in 1999. On physical examination the patient was afebrile. There was a 4 × 3 cm scaly, firm, freely mobile mass over the prepatellar region of his right knee (Fig 1). The mass was nontender to palpation and without drainage. The skin overlying the lesion was hyperpigmented. Active and passive knee ROM was full, symmetric, and painless. There was no knee effusion and the distal neurovascular examination was normal. There was no inguinal adenopathy.Fig 1.: Clinical appearance of lesion over prepatellar region of right knee.Admission laboratory data including complete blood count, erythrocyte sedimentation rate, and metabolic panel were normal. Imaging studies included plain radiographs and MRI scans (Figs 2–5).Fig 2.: Sagittal T1-weighted image shows the lesion.Fig 3.: T2-weighted axial image shows the mass.Fig 4.: Sagittal short tau inversion recovery image that shows the lesion clearly.Fig 5.: Axial fat suppressed T1-weighted image with gadolinium showing rim enhancement of the lesion.Based on the history, physical examination, and imaging studies, what is the differential diagnosis? RADIOLOGIC INTERPRETATION Radiographs of the knee were obtained and showed no evidence of bony erosions of the patella or soft tissue calcifications. Sagittal T1-weighted (589/16) (Fig 2) spin-echo and axial turbo spin echo T2-weighted (3500/90) (Fig 3) MRI scans show a relatively well-defined, lobulated, superficial soft tissue mass anteromedial to the patella (arrow, Fig 2), overlying portions of the medial retinaculum and infrapatellar tendon. The sagittal STIR (short-tau inversion recovery: (4500/75/100) (Fig 4) MRI scan delineates the lesion best. Axial fat-suppressed T1-weighted (663/16) (Fig 5) MRI scans obtained after the administration of intravenous contrast show predominately peripheral enhancement compatible with a cystic lesion. DIFFERENTIAL DIAGNOSIS Based on the radiographs, the differential diagnostic considerations in this case may seem extensive. However, when analyzed in the context of the clinical presentation, patient age, lesion location, and salient radiologic features, the differential is limited and includes the following: Sarcoma (subcutaneous malignant fibrous histiocytoma or dermatofibrosarcoma protuberans) Tumoral calcinosis Inflammatory lesions (abscess) Gout Hemangioma or lymphangioma Pilomatrixoma The lesion was biopsied and studied histologically (Figs 6–9). Based on the history, physical examination, imaging studies, and histologic picture, what is the diagnosis and how should this lesion be treated?Fig 6.: Hemisected gross specimen of prepatellar mass is shown.Fig 7.: Low power photomicrograph of the lesion (Stain, hematoxylin and eosin; magnification, ×100).Fig 8.: Low power photomicrograph of the lesion (Stain, hematoxylin and eosin; magnification, ×150).Fig 9.: Higher power photomicrograph of the lesion (Stain, gomori methenamine silver; magnification, ×400).HISTOLOGY The hemisected gross specimen showed nodules with central necrosis and surrounding fibrosis and hemorrhage (Fig 6). Low power hematoxylin and eosin stained slides (Figs 7, 8) showed a fibrovascular stoma on the periphery with a region of central necrotic tissue. Chronic inflammatory cells, necrotic debris, budding hyphae and spores can be visualized throughout the slides. Gomori methenamine silver stain histomicrograph showed spores and budding hyphae (Fig 9). DIAGNOSIS Majocchi’s granuloma TREATMENT AND DISCUSSION Majocchi 4 first described an intercutaneous or subcutaneous granulomatous inflammation arising from local invasion by a dermatophyte in 1883. The lesion was termed Majocchi’s granuloma. There are two main forms of Majocchi’s granuloma: a small perifollicular papular form and a deep subcutaneous nodular form. The superficial form typically is encountered on the legs of immunologically healthy individuals, especially women who shave their legs, and men after prolonged skin maceration from wearing combat boots. The deep nodular form is present in patients who have immunosuppression and typically presents as a group of firm or fluctuant nodules 6 (Fig 9). Majocchi’s granuloma primarily is a disease of adults and is more common in women. The lesion typically is unilateral and presents as a plaque of erythema and scaling on a limb with small nodules or pustules around the hair follicle. The lesion has indistinct borders, a scaly texture, and is darker in coloration than the surrounding skin. The invasive infection, or deep form, is linked to underlying systemic conditions such as leukemia, lymphosarcoma, diabetes mellitus, dysproteinemia, Cushing syndrome, and the administration of exogenous steroids or immunosuppressive agents. 5 Etiologically, the granuloma is thought to arise from hypheal invasion within the cornified keratinocyte of the hair follicle precipitating a suppurative folliculitis with rupture of the hair follicle and it’s contents into the dermis, producing a granulomatous dermal response. 3 Trichophyton rubrum is the most common fungus causing the granuloma. 8 Histologic evaluation of the lesion shows necrotic areas containing fungal elements surrounded by polymorphonuclear leukocytes, epithelioid cells, giant cells, fibroblasts, lymphocytes, and plasma cells. The epidermis often appears ulcerated or hyperplastic. Magnetic resonance imaging typically reveals a heterogeneous mass with hypointense signal intensity on T1-weighted images and hyperintense signal changes on T2-weighted images. Gadolinium produces diffuse enhancement peripherally with central nonenhancing areas. Treatment involves the use of systemic antifungal agents such as griseofulvin, ketoconazole, or terbafine. Topical antifungals are inadequate because they cannot reach the fungus in the dermal layer. Surgical excision, because of its high cure rate, is the gold standard for treatment of primary cutaneous deep fungal infections in patients who are immunocompromised. 1 This patient had the deep nodular form of Majocchi’s granuloma that is common in patients who are immunosuppressed. The patient’s diabetes mellitus and kidney transplant were predisposing factors for this fungal infection. He had surgical resection of the lesion and was given oral ketoconazole. In this case, Candida was the etiologic organism and to the authors’ knowledge has not been described previously as a cause for Majocchi’s granuloma. At the latest followup, this patient remains free of recurrent infection.