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Table 1 Differential Diagnosis of Solitary Fibrous Tumor

From: The many faces of solitary fibrous tumor; diversity of histological features, differential diagnosis and role of molecular studies and surrogate markers in avoiding misdiagnosis and predicting the behavior

  Age (years) M:F ratio Sites Histological features IHC Key genetic alterations
Solitary Fibrous Tumor [10, 21] 40 to 70 Equal Pleura
Meninges; CNS & spinal cord
Deep soft tissues of extremities
Abdominal cavity, the pelvis, or the retroperitoneum
Head and neck
Trunk
Patternless spindled to ovoid cells within a variably collagenous stroma, admixed with branching and hyalinized staghorn-shaped (hemangiopericytomatous) blood vessels. CD34+, STAT6+ fusion of the NAB2 and STAT6 genes
Synovial Sarcoma, Monophasic [14, 21] Adolescents & young adults (2/3rds < 50 years) 1.2:1 Most often deep soft tissues of extremities or limb girdles, distal extremities (fingers, hand foot), Head and & Neck Fascicles & sheets of uniform spindle cells. May have a herringbone pattern. HPC like branching vessels are common. Often contain stromal hyalinized or wiry collagen bundles SYT +, TLE1+, EMA+, CK+,
STAT6-
SYT-SSX1/2
Malignant Peripheral
Nerve Sheath Tumor [21, 66]
20–50
(median 35)
Equal Trunk and extremities, followed by the head and neck area Hypercellular & hypocellular fascicles of spindle-shaped cells (marbleized pattern), perivascular accentuation, HPC-like vascular pattern, increase mitoses, geographic necrosis, heterologous differentiation in 15% of cases S100 + (< 50%), SOX10 + (< 70%)
GFAP+ (20–30%)
H3K27me3 Loss
NF1, CDKN2A/CDKN2B, and PRC2 core components (EED or SUZ12) mutations
Dedifferentiated Liposarcoma [67] 27–81
(mean age 52)
Equal Retroperitoneum, spermatic cord and (more rarely) mediastinum, head and neck, and trunk. Fascicles or sheets of atypical spindle cells along with lipogenic component with atypia MDM2+, CDK4+, p16+, CD34+/−, STAT6−/+ MDM2 & CDK4 amplification
Sarcomatoid Mesothelioma [65] 41–94
(median 70)
22:1 Pleura, Peritoneum Fascicles or haphazardly distributed atypical spindle cells with increase mitoses. Densely collagenized stroma with hypocellular atypical spindle cells in desmoplastic mesothelioma CK+, EMA+, D2–40 +, Calretinin+, WT1 + BAP mutation
Soft Tissue Angiofibroma [68] Middle age, peak in 60th decade 0.75:1 Usually subcutis of extremities, particularly involving around large joints like knee Variably myxoid to collagenous stroma, branching capillary network & uniform bland spindle cells with ovoid or tapering nuclei. Perivascular collagenization EMA −/+,
CD34 −/+
AHRR-NCOA2
Spindle Cell Lipoma [69] 40–60 10:1 Subcutis of posterior neck, upper back & shoulders
Face, scalp, orbit, oral cavity & extremities rarely involved
Short fascicles of bland spindle cells with short stubby nuclei, variable number of adipocytes, and ropy collagen bundles. Fibromyxoid stroma, mast cells CD34+, ASMA -, Desmin -, S100- RB1 deletion
Myofibroma [70] First decade (< 2 years)
Adults
2:1
Equal
Skin & subcutis of extremities, head & neck & trunk.
Infantile cases involve liver, heart, GIT, brain & bone
Distinctive biphasic pattern with nodules comprising of immature spindle cells in center with HPC-like vasculature and whorls of myoid cells at periphery with a basophilic pseudochondroid appearance ASMA+/−, CD34 −/+, Desmin + Nil
Myofibroblastoma [71] 50–60
(median 54)
2:1 Most cases involve Inguinal/groin area (vulva/vagina, perineum, and scrotum) Short fascicles of spindle cells with short stubby nuclei, interspersed broad collagen bands & variable admixture of mature adipocytes CD34+, Desmin +
ASMA+/−
RB1 deletion
Cellular Angiofibroma [71] 5th decade in women, 7th decade in men Equal Vulvovaginal/ inguinoscrotal & paratesticular region Randomly distributed short, intersecting fascicles of spindle cells containing stubby nuclei. Scattered medium sized hyalinized vessels. Wispy stromal collagen ER & PR + (50%), CD34+/−, Desmin −/+, ASMA −/+ RB1 deletion
Deep Fibrous Histiocytoma [21] 6–84
(median 37)
Slightly more in male Extremities followed by head and neck region Uniformly cellular storiform to short fascicular pattern of plump spindle cells. HPC-like branching vessels, stromal hyalinization CD34 + (40%), ASMA f+/−, STAT6 - Nil
Dermatofibrosarcoma
Protuberans [75]
20–40 Slight male Trunk, proximal extremities, head and neck region, genital area, the breast, and at acral sites Dermal uniform spindle cells arranged in storiform, whorls & short fascicles. Infiltration of results in “honeycomb” appearance. CD34+, ASAMA +/−, STAT6 - COLIA-PDGFB
Cellular Schwannoma [66] 40–60 Equal Paravertebral, retroperitoneum, pelvis & mediastinum Predominantly or exclusively composed of Antoni A areas with interlacing fascicles of spindle cells having tapered nuclei. Hyalinized vessels are focally seen S100+, SOX10+, STAT6- NF2 mutations