Controversial issues in soft tissue solitary fibrous tumors: A pathological and molecular review.

The clinical evolution of solitary fibrous tumor (SFT) remains unclear. Although various clinical, morphological and molecular criteria may indicate increased risk of malignancy, some SFT can still progress despite having a clearly benign appearance. Various risk stratification systems have been proposed, but unfortunately they are not sufficient to precisely determine the malignant potential. In this review, we discuss current knowledge on SFT, focusing on the following controversial issues: (i) the diverse morphologic spectrum: 'the great simulator;' (ii) malignant transformation or dedifferentiation; (iii) current risk stratification systems; and (iv) molecular factors associated with clinical evolution. The morphological spectrum of SFT and the list of differential diagnoses continue to expand. Both have increased considerably since the first descriptions of specific molecular alterations. A classification of malignant SFT should not be based on histology alone. The correlation of all pathological and molecular factors is recommended; its inclusion in risk stratification systems may help to improve diagnosis and prognosis.

[Bone and soft tissue Langerhans cell histiocytosis with multinucleated giant cells and BRAF V600E mutation]. / Histiocitosis de células de Langerhans de partes blandas y hueso con células gigantes multinucleadas y mutación BRAF V600E.

Langerhans cell histiocytosis (LCH) is a heterogeneous disease characterized by proliferation of Langerhans cells and BRAF mutation in almost half of the cases. Bone involvement is common but large soft tissue disease is uncommon. We report a pediatric patient with a large tumor mass involving the left iliac bone and the adjacent soft tissue. The computed tomography scan showed an osteolytic lesion with soft tissue extension. Surgical curettage of the lesion was performed and the final histopathologic diagnosis was LCH with CD1a immunoreactivity in tumor cells. The molecular analysis revealed a BRAF V600E mutation. We discuss the histopathological and immunohistochemical differential diagnosis with histiocytosis other than LCH.

[Extraovarian granulosa cell tumor with FOXL2 mutation. Morphological and immunohistochemical differential diagnosis]. / Tumor de células de la granulosa extraovárico con mutación FOXL2. Diagnóstico diferencial morfológico e inmunohistoquímico.

Extraovarian granulosa cell tumor is a very uncommon tumor and the identification of a recurrent mutation in FOXL2 may be used as another diagnostic tool along with the classical morphological and immunohistochemical findings. Here, we report a new case of extraovarian granulosa cell tumor in a 57 years old female patient presented with a sub-hepatic mass and abdominal pain. Histopathological examination of the excised mass showed features of adult-type granulosa cell tumor with α-inhibin, calretinin, WT1, S100, CD99 and progesterone receptor immunoreactivity. A FOXL2 mutation was detected on molecular biology study. A final diagnosis was an extraovarian adult-type granulosa cell tumor. We discuss the histopathological and immunohistochemical differential diagnosis.