A study of collagen refractility in dermatofibroma and dermatofibrosarcoma protuberans using diffractive microscopy.

BACKGROUND: Diffractive microscopy creates contrast within samples that are otherwise uniform under bright light. This technique can highlight subtle differences in refractive indices within birefringent samples containing varying amounts of mature collagen. Dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) possess differences in their mature collagen content and, therefore, may be distinguishable using diffractive microscopy. METHODS: Two hundred forty-two DF and 85 DFSP hematoxylin-eosin (H&E)-stained specimens were analyzed using diffractive microscopy. Data regarding the distribution pattern and strength of refractility was recorded. RESULTS: DFSP was more frequently found to be focally, weakly, or non-refractile (82.9%; n = 68) under diffractive microscopy, while DF more often showed diffusely bright refractility (52.9%; n = 128). DFSP samples with diffuse refractility in portions of the lesion (17.1%; n = 14) also exhibited a unique checkerboard pattern distinct from that which was seen in DF samples. CONCLUSIONS: The absence of diffuse refractility was more closely associated with DFSP, as was the presence of a unique checkerboard diffraction pattern. Despite high sensitivity (Sn = 82.9%), absent refractility was not a specific test (Sp = 52.9%), with 47.1% (n = 114) of DF samples sharing this feature. The distinction between DF and DFSP is often diagnosed using H&E alone. In difficult cases, examination of collagen under diffractive microscopy may be useful in distinguishing DFSP from DF and provide an alternative cost-effective tool to immunohistochemical staining.

Epidermal inclusion cyst embedded in benign fibrous histiocytic lesion with prominent epithelioid morphology.

Benign fibrous histiocytoma also known as dermatofibroma is one of the common mesenchymal neoplasms. It commonly develops in young adult with female predominance and predilection for the extremities, particularly lower extremities. Implantation of epidermis in the dermis or subcutaneous tissues may lead to the formation of epidermal inclusion cyst, which is the most common type of epithelial cyst. Development of epidermal inclusion cyst within a benign fibrous histiocytoma is a rare occurrence. This is a unique case of two unrelated lesions.

Connexin 43 in Dermatofibroma and Dermatofibrosarcoma Protuberans: Diagnostic, Pathogenic, and Therapeutic Implications.

ABSTRACT: Connexins play a crucial role in the formation of gap junctions that connect cells to each other, as well as cells to the surrounding environment. In recent years, connexin 43 has been extensively studied in various human tumors. In this study, we conducted an immunohistochemical analysis to evaluate the expression of connexin in 16 dermatofibromas (DFs) and 13 dermatofibrosarcoma protuberans (DFSP). Connexin was diffusely expressed in the cytoplasm of all DFs with moderate or strong intensity, whereas all DFSPs showed negative staining. In addition to its diagnostic implications, the loss of Cx43 may elucidate the invasive capacity of DFSP and offer a potential avenue for future therapeutic interventions.

Dermatofibroma Versus Dermatofibrosarcoma Protuberans: A Nuclear Morphology Study.

ABSTRACT: The locally invasive soft-tissue sarcoma, dermatofibrosarcoma protuberans (DFSPs), shares certain histologic features of the much more common and benign dermatofibroma (DF). While immunohistochemical stains, specifically cluster of differentiation 34 and Factor XIIIa, can be used to distinguish the 2 entities using microscopy, these markers are not entirely sensitive nor specific. Three-dimensionally, DFSP nuclei resemble a "puck" or "coin"-like shape. As hematoxylin/eosin-stained slides are prepared, these "puck" nuclei are fixed in an infinite number of orientations depending on their current position in rotation about their axes within the tumor cells. Under histological examination, this random nuclear positioning produces the appearance of 2 predominate morphologies: an ovoid "disk" shape (en face) and a narrow spindled shape (side view), which distribute in a roughly 50:50 ratio throughout the tumor sample slide. Nuclear morphology was analyzed in 324 DFSP and DF samples at high magnification (×400) to determine the presence or absence of a predominant morphology in which nuclei appear to alternate between an ovoid (en face) and spindled (side view) throughout most of the tumor sample. An alternating ovoid-spindled nuclear morphology was the predominant cytology in 98% of DFSP and was not predominant in 100% of DF samples (P < 0.001). This morphology was found to be highly specific (Sp = 1) and sensitive (Sn = 0.98) for DFSP. This unique nuclear morphology may be a more sensitive and specific diagnostic tool in identifying DFSP from DF in comparison with costly immunohistochemical stains.

Benign fibrohistiocytic jaw lesions: a 48-year clinicopathologic analysis and review of the literature.

OBJECTIVE: Intra-osseous fibrohistiocytic lesions have long been reported in the literature; evidence suggests they represent a heterogeneous group of reactive and neoplastic processes. This study evaluated a series of gnathic fibrohistiocytic lesions to identify and categorize their clinical, radiographic and morphologic spectrum. STUDY DESIGN: A retrospective case search over 48 years was conducted for maxillary and mandibular intra-bony fibrohistiocytic lesions. Diagnoses were confirmed and demographic, radiographic, clinical and follow-up data was analyzed. RESULTS: Fifty cases met the inclusion criteria. Most cases (80%) were found in the second through fourth decades (mean, 29 years). The most common location (86%) was the posterior mandible. Radiographic presentations varied, but a few patterns emerged, including a distinctive mottled, honeycomb type with punctate lucencies. All cases demonstrated fibrous components admixed with variable histiocytes. Eight cases (16%) were histiocyte-rich with dominant sheets of xanthoma cells. Immunohistochemical staining revealed strong CD68 and CD163 expression, along with variable smooth muscle actin staining. The vast majority (92%) of cases were treated conservatively. Available follow-up showed lesional stability in 17 cases (average, 85 months) with 2 recurrences (24 months each) and no evidence of malignant transformation. CONCLUSIONS: This study is the largest to date of fibrohistiocytic gnathic lesions, revealing distinctive radiographic and histologic findings and characteristic clinical and immunophenotypic features. Available evidence suggests that most of these are indolent, slow-growing lesions amenable to conservative therapy.

Dermatofibroma with Verocay Body-Type Palisading Features and a Brief Discussion on Potential Schwannoma Mimickers of the Skin.

Several types of cutaneous tumors can show palisading features or the so-called rippled pattern. The list includes adnexal tumors such as trichoblastoma and sebaceoma, basal cell carcinoma, leiomyoma, perineuroma, myofibroblastoma, and even malignant melanoma. Dermatofibroma, which is known for having a large variety of histological patterns, is also in the list. Here we present a case of dermatofibroma with palisading features strikingly similar to Verocay bodies of schwannoma.

Diagnostic utility of ERG immunostaining in dermatofibroma.

AIMS: Dermatofibroma/fibrous histiocytoma (DF/FH) is a common cutaneous mesenchymal neoplasm exhibiting benign biological behaviour. However, the immunohistochemical utility of erythroblast transformation-specific-related gene (ERG) for diagnosing DF remains unknown. The authors reviewed the immunohistochemical status of ERG in different subtypes of DF and in its differential diagnoses. METHODS: Overall, 97 cases of ordinary DF/FH, 6 cases of aneurysmal FH, 10 cases of cellular FH, 5 cases of angiomatoid FH, 2 cases of epithelioid FH, 64 cases of dermatofibrosarcoma protuberans (DFSP) and 52 cases of fibrous scar were retrieved. As the other histological types of cutaneous neoplasms, 6 cases of myxofibrosarcoma, 4 cases of undifferentiated pleomorphic sarcoma, 11 cases of atypical fibroxanthoma, 19 cases of malignant melanoma, 20 cases of nevocellular nevus, 20 cases of neurofibroma, 19 cases of schwannoma, 8 cases of angioleiomyoma and 1 case of pilar leiomyoma were included. RESULTS: Immunohistochemical positivity for ERG was demonstrated in 87 of 97 cases (89.6%) of ordinary DF/FH, 7 of 10 cases (70%) of cellular FH, 3 of 6 cases (50%) of aneurysmal FH, 1 of 5 cases (20%) of angiomatoid FH and 1 of 52 cases (0.1%) of fibrous scar. All cases of DFSP, epithelioid FH and other types of cutaneous neoplasms included in the current investigation were negative for ERG. The intensity of ERG immunohistochemical staining in spindle-shaped cells appeared weaker than that in endothelial cells. CONCLUSIONS: DF/FH was frequently positive for ERG immunostaining. ERG immunostaining may thus be useful to distinguish DF/FH from DFSP.

Efficacy of a Fractionated 1540-nm Erbium Glass Laser in the Treatment of Dermatofibromas.

BACKGROUND: Treatment of dermatofibromas, beyond surgical excision, has remained inadequate and elusive. Nonsurgical treatment options are desired by both patients and physicians. Erbium glass lasers are known for targeting and remodeling the dermis but have not yet been studied for the treatment of dermatofibromas. OBJECTIVE: To evaluate the efficacy and safety of the fractional 1540-nm erbium glass laser for treatment of dermatofibromas. METHODS: Thirty-five patients representing 44 dermatofibromas completed 2 consecutive monthly treatments with a non-ablative, fractional 1540-nm erbium glass laser and were evaluated at 4, 8, and 12 weeks after the initial treatment. Dermatofibromas were evaluated using patient surveys given before and after the treatments. RESULTS: By week 4, patients reported improvement in color and texture of the dermatofibromas. These improvements were durable through week 12. No complications were reported. CONCLUSIONS: This study demonstrates that the fractional 1540-nm erbium glass laser may be used to improve the color and texture of dermatofibromas and achieve positive patient reported outcomes after only 2 treatments. J Drugs Dermatol. 2022;21(11):1201-1205. doi:10.36849/JDD.6287.

Epithelioid fibrous histiocytoma: three diagnostically challenging cases with novel ALK gene fusions, unusual storiform growth pattern, and a prominent spindled morphology.

Epithelioid fibrous histiocytoma (EFH) is a distinctive cutaneous neoplasm with a relatively variable morphological appearance. Recently, it has been shown that this tumor is molecularly characterized by ALK gene fusions. We report three EFHs with unusual histological presentation represented by a prominent/predominant spindle cell proliferation arranged in a variably storiform/whirling architectural pattern with or without stromal sclerosis. One of the cases closely resembled cellular fibrous histiocytoma. All three cases were immunohistochemically ALK-positive and were analyzed for ALK gene rearrangements using a next-generation sequencing-based assay (FusionPlex Sarcoma Kit, ArcherDx). Three novel fusions, namely AP3D1::ALK, COL1A::ALK, and LRRFIP2::ALK, were detected and further confirmed by FISH in all 3 cases and RT-PCR in 1 case. All patients were elderly (62-63 years) and presented with a solitary polypoid lesion on the extremities. The awareness of these morphological variants is important since it entertains a wide and slightly different differential diagnosis than conventional EFH. We also presented evidence that a clear separation of EFH from BFH in all cases may not be as straightforward as previously thought. The consistent ALK immunoexpression and the continually expanding scale of ALK gene rearrangements provide a useful tool to distinguish EFH from its histologic mimics.

Benign fibrous histiocytoma of the medial rectus muscle.

We report the case of a healthy 17-year-old girl who underwent surgery for excision of a painless, rapidly enlarging subconjunctival mass. The mass was found to be tightly adherent to the medial rectus muscle of the left eye, requiring extensive dissection. Histopathology revealed a mass of bland and foamy spindle cells in a storiform pattern that was positive for CD68, PGM1, and factor XIIIA and negative for S-100. The clinical and histopathologic findings are consistent with benign fibrous histiocytoma.