Clinical, pathologic, and molecular analyses of superficial low-grade fibromyxoid sarcoma in two young patients: A rare and deceptive mimic of benignancy.

Low-grade fibromyxoid sarcoma (LGFMS) is a histopathologically deceptive soft tissue neoplasm with bland cytology, which is typically encountered in deep soft tissue of adults. We report two cases of superficial LGFMS in young patients (16 and 21 years old, respectively), which were difficult to diagnose on histopathologic and clinical findings alone. LGFMS commonly mimics benign neoplasms such as cellular neurothekeoma, fibromatosis, neurofibroma, and perineurioma. Malignancies included in the differential diagnosis are soft tissue neoplasms such as dermatofibrosarcoma protuberans and myxofibrosarcoma. A high degree of reported variation in pattern and cellularity among LGFMS further complicates the diagnosis. Careful examination and appropriate immunohistochemistry panels including MUC4 are essential for narrowing the differential diagnosis. Molecular studies for possible FUS translocation can confirm the diagnosis of LGFMS. Sufficient sampling and workup of these lesions are critical, especially in younger patients. Young age and superficial presentation can easily sway dermatopathologists/dermatologists toward an incorrect diagnosis of benignancy.

Shapiro xanthogranuloma: An essential diagnosis for dermatologists and dermatopathologists to recognize to avoid misdiagnosis of a hematopoietic malignancy in infants and neonates.

The Shapiro xanthogranuloma is a histopathologic form of xanthogranuloma that shows closely packed monomorphous cells, which can extend into the subcutaneous fat; it usually lacks routine diagnostic features of xanthogranuloma. Herein we describe two cases of Shapiro xanthogranuloma occurring in a neonate and in an infant, which were initially thought to be hematologic malignancies. One patient's presentation as a "blueberry muffin baby" added to the diagnostic confusion. Pediatric dermatologists, dermatologists, and dermatopathologists need to be aware of the Shapiro xanthogranuloma and its clinicopathologic features to avoid misdiagnosis of a hematopoietic malignancy in neonates and infants.

Angiokeratoma-like purpuric palmar nodules following chemotherapy.

We describe a patient with leukemia undergoing chemotherapy who developed painful purpuric nodules of the digits. These findings were concerning for endocarditis (clinically) and angiokeratomas on gross histology. After extensive evaluation, we report the development of painful purpuric nodules as a likely side effect of the patient's therapeutic regimen (hydroxyurea, danorubicin, cytarabine, and methotrexate).

The difficulty in interpreting gene expression profiling in BAP-negative melanocytic tumors.

BACKGROUND: BAP-negative melanocytic tumors were unrecognized in the medical literature until 2011. While the clinical significance of these tumors is poorly understood, there is concern such lesions represent processes in transition, and malignant degeneration is a concern. We investigated use of a 23-gene expression profiling (23-GEP) test for distinction from melanoma with the aim of better characterizing the biologic potential of such tumors. METHODS: Twenty BAP-negative melanocytic tumors, subjected to 23-GEP (Myriad Genetic Laboratories, Inc. [Salt Lake City, Utah]) testing, were retrospectively analyzed. RESULTS: Tumors exhibited varying degrees of atypia and aberrant immunohistochemical profiles. 23-GEP testing revealed a "malignant" genetic signature in four cases, a "benign" signature in 15 cases, and an "indeterminate" signature in one case. Array-based comparative genomic hybridization (aCGH) testing was performed for two cases with a "malignant" 23-GEP signature, but the aCGH result conflicted with 23-GEP, and supported benignity. Conversely, in one case with a "benign" 23-GEP result, aCGH testing supported assessment as melanoma. Moreover, evolving melanoma could not be wholly excluded by histopathological analysis in 2 "benign" cases. CONCLUSIONS: BAP-negative melanocytic tumors remain a diagnostic dilemma for dermatopathologists. A widely marketed 23-GEP test may not be useful in distinguishing these tumors from spitzoid melanoma, at least in comparison to aCGH technology.