Diagnosis of desmoid-type fibromatosis (DF) may be challenging on biopsy due to morphologic overlap with reactive fibrosis (scar) and other uniform spindle cell neoplasms. Evaluation of nuclear β-catenin, a surrogate of Wnt pathway activation, is often difficult in DF due to weak nuclear expression and high background membranous/cytoplasmic staining. Lymphoid enhancer-factor 1 (LEF1) is a recently characterized effector partner of β-catenin which activates the transcription of target genes. We investigated the performance of LEF1 and β-catenin immunohistochemistry in a retrospective series of 156 soft tissue tumors, including 35 DF, 3 superficial fibromatosis, and 121 histologic mimics (19 soft tissue perineurioma, 8 colorectal perineurioma, 4 intraneural perineurioma, 26 scars, 23 nodular fasciitis, 6 low-grade fibromyxoid sarcomas, 6 angioleiomyomas, 5 neurofibromas, 5 dermatofibrosarcoma protuberans, 3 low-grade myofibroblastic sarcomas, 3 synovial sarcomas, 3 inflammatory myofibroblastic tumors, 2 schwannomas, and 1 each of Gardner-associated fibroma, radiation-associated spindle cell sarcoma, sclerotic fibroma, dermatofibroma, and glomus tumor). LEF1 expression was not only seen in 33/35 (94%) of DF but also observed in 19/23 (82%) nodular fasciitis, 7/19 (37%) soft tissue perineurioma, 2/3 (66%) synovial sarcoma, and 6/26 (23%) scar, as well as in 1 radiation-associated spindle cell sarcoma. The sensitivity and specificity of LEF1 IHC for diagnosis of DF were 94% and 70%, respectively. By comparison, β-catenin offered similar sensitivity, 94%, but 88% specificity. Positivity for LEF1 and β-catenin in combination showed sensitivity of 89%, lower than the sensitivity of β-catenin alone (94%); however, the combination of both LEF1 and β-catenin improved specificity (96%) compared to the specificity of β-catenin alone (88%). Although LEF1 has imperfect specificity in isolation, this stain has diagnostic utility when used in combination with β-catenin.

Pachydermodactyly (PDD), meaning "thick skin finger" in Greek, is a rare, noninflammatory, benign, superficial fibromatosis. We report the case of PDD in a 15-year-old boy who visited our clinic because of asymptomatic swelling of the proximal interphalangeal (PIP) joints on the third finger of both left and right hands. Physical examination revealed thickening of the skin in the radial and ulnar aspects of the PIP joints of his third finger of both hands without functional limitation or neurological symptoms. He had a habit of biting his swelling fingers, and he belonged to a basketball club at his junior high school. He had no medical history. Plain radiographs and magnetic resonance imaging of both hands showed only soft tissue thickening outside of the radial and ulnar collateral ligament of the bilateral third PIP joint. The lesions were suggestive of PDD. Surgical resection was performed via a midaxial incision and a Z-plasty to confirm the diagnosis and improve the aesthetic appearance of his hands. Histopathological examination of the lesions was compatible with PDD. After surgery on the left hand, the patient underwent the same surgery on the right hand. No recurrence or complications were observed at the one-year follow-up after surgical intervention. Thus, surgery for PDD via a midaxial incision may be a good treatment option for patients who wish to rectify the appearance of their digital deformity.

Pachydermodactyly is a rare and benign superficial fibromatosis characterized by painless and progressive swelling of periarticular soft tissues of the proximal interphalangeal (PIP) joints, most commonly of both hands. There is no tenderness, warmth, morning stiffness, or reduced range of motion associated. Our purpose is to highlight the diagnostic utility of ultrasonography, superb microvascular imaging (SMI), and elastography in pachydermodactyly. We report the case of a 15-year-old adolescent white boy, with a 6-month history of insidious and progressive, asymptomatic swelling of the lateral and dorsal regions of the metacarpophalangeal (MCP), and PIP joints of both hands. Articular ultrasonography showed thickening of the skin around the lateral regions of the PIP and MCP joints, with no synovitis, hydrarthrosis, or muscle, tendon, or bone changes. Strain elastography revealed lower elasticity in the aforementioned skin regions, corresponding to increased tissue hardness due to hyperkeratosis. No SMI or Doppler signals were detected in epidermal or dermal tissues, as well as in tendons, joints, and bone. This case report shows that ultrasonography, SMI, and elastography may play a significant role in the accurate diagnosis of pachydermodactyly and exclusion of alternative conditions. These imaging modalities have no ionizing radiation; they are fast, inexpensive, and performed on site. They do not require usage of contrast agents and thus can eliminate the need of invasive procedures such as skin biopsy. They also contribute to reduce health care costs with unnecessary complementary tests and inappropriate treatment.

Superficial fibromatosis exhibits variable MR signal intensity due to collagenous and fibroproliferative components. Quantifying this signal heterogeneity using image texture analysis and T2-mapping could have prognostic and therapeutic implications. This IRB-approved retrospective study included 13 patients with superficial fibromatosis, managed by observation, electron beam radiotherapy (EBT), or pentoxifylline/vitamin E. Two-dimensional regions of interest (ROIs) were drawn on proton-density or T2-weighted MRI for radiomics feature analysis, and corresponding T2-maps. Comparisons were made between baseline and follow-up T2 relaxation times and radiomics features: Shannon's entropy, kurtosis, skewness, mean of positive pixels (MPP), and uniformity of distribution of positive gray-level pixel values (UPP). There were 19 nodules in 13 subjects. Mean patient age was 60 years; 62% (8/13) were female; mean follow-up was 9.7 months. Nodule diameter at baseline averaged 18.2 mm (std dev 16.2 mm) and decreased almost 10% to 16.6 mm (p = 0.1, paired t-test). Normalized T2 signal intensity decreased 23% from 0.71 to 0.55 (p = 0.03, paired t-test). T2 relaxation time decreased 16% from 46.5 to 39.1 ms (p < 0.001, paired t-test). Among radiomics features, skewness increased to 0.71 from 0.41 (p = 0.03, paired t-test), and entropy decreased from 8.37 to 8.03 (p = 0.05, paired t-test); differences in other radiomics features were not significant. Radiomics analysis and T2-mapping of superficial fibromatosis is feasible; robust decreases in absolute T2 relaxation time, and changes in image textural features (increased skewness and decreased entropy) offer novel imaging biomarkers of nodule collagenization and maturation.

Fibromatoses encompass a broad group of histopathologically similar fibroblastic/myofibroblastic proliferations with divergent clinical manifestations and behavior. Deep (desmoid-type) fibromatoses are typically large, rapidly growing, and locally aggressive tumors that occur in the abdominal wall, mesentery, and extra-abdominal soft tissue, principally the musculature of the trunk and extremities. Most sporadic cases of desmoid fibromatosis harbor inactivating mutations in CTNNB1, the gene encoding beta-catenin. Tumors occurring in the context of familial adenomatous polyposis and Gardner syndrome bear inactivating mutations in APC. By contrast, mutations in CTNNB1 or APC have not been identified in cases of superficial fibromatosis. Cutaneous involvement by desmoid fibromatosis is exceedingly rare. Here we present a 78-year-old male with desmoid-type fibromatosis arising in the dermis of the right medial calf with a pathogenic mutation in CTNNB1 and a variant of unknown significance in APC.