*Contributed equally
Lipidized fibrous histiocytoma (FH) is a rare type of FH. The present study aimed to describe the clinical and pathological features of lipidized FH. A total of eight patients diagnosed with lipidized FH were retrospectively reviewed in the present study. The cohort included three male and five female patients (male to female ratio, 1.7:1) with a mean age of 48 years (range, 38-62 years). In total, four tumors were located on the buttock, three on the lower leg and one on the forearm. Histological, lipidized FH showed a wide spectrum. Some cases included prominent stromal hyalinization and hyalinized vessels with scant lipid-laden histiocytes. Other cases exhibited the prominent lipid-laden histiocytes and scant stromal hyalinization. Overall, lipidized FH must be differentiated from other benign and malignant tumors, taking into account the therapeutic and prognostic differences between these different entities.
Benign fibrous histiocytoma (FH), also known as dermatofibroma, is one of the most common benign tumors of the skin worldwide (
By definition, lipidized FHs consist of abundant lipid-laden histiocytes and distinctive stromal hyalinization (
Clinical data were collected from the medical records of eight patients diagnosed with lipidized FH from November 2019 to November 2021. The diagnosis was confirmed by Dr Zhao Ming (Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China). A total of three cases originated from the tissue bank of the Department of Pathology of the Peoples' Liberation Army 989 Hospital (Pingdingshan, China), four cases originated from the tissue bank of Fenlan Medical Laboratory (Hangzhou, China) and one case originated from the tissue bank of Department of Pathology of Yexian People's Hospital (Pingdingshan, China). The cohort included three male and five female patients (male: female ratio, 1.7:1) with a mean age of 48 years (range: 38-62 years). The present study was approved by the 989 Hospital Medical Ethics Committee, Fenlan Lab Medical Ethics Committee and Yexian First People's Hospital Committee. All participants signed an informed consent form and all patient data were anonymized. The inclusion criterion was a diagnosis in accordance with lipidized FH.
Hematoxylin and eosin-stained slides were available for all cases and this staining was conducted using a method described by Sommer
Sections (4-µm) from paraffin blocks were also stained immunohistochemically using BOND-MAX Automated IHC/ISH Stainer (Leica Microsystems GmbH). Sections were mounted onto slides, air dried for 20 min and baked at 60˚C for 20 min. The heat-induced antigen retrieval method was performed using Tris-EDTA buffer (1X; cat. no. #K0071; Shanghai Jiehao Biotechnology Co., Ltd.) and endogenous peroxidase activity usually responsible for background staining, was quenched with 3% peroxidase-blocking reagent, (Henan Celnovte Biotechnology Co., Ltd.), which was applied at 37˚C for 10 min. The slides were incubated with the following commercially available antibodies: CD68 (cat. no. CCR-0702; KP1; 1:1,000), smooth muscle actin (cat. no. CAM-0190; IA4; 1:50), S-100 protein (cat. no. CSM-0101; polyclonal; 1:500), CD34 (cat. no. CCM-0550; QBend10; 1:50), desmin (cat. no. CDM-0021; D33; 1:50), MUC4 (cat. no. CMM-0270; 8G7; 1:50) and cytokeratin (cat. no. CCM-0960; AE1/AE3; 1:50) at 37˚C for 30 min. All antibodies were purchased from Henan Celnovte Biotechnology Co., Ltd. The sections were then examined using a light microscope. Tissue sections were then washed (2x6 min) and incubated with Microstacker™ + Linker in room temperature for 15 min for signal amplification. After TBS washing (2x6 min), Microstacker™ Flex HRP-polymer detection reagent (ready-to-use; cat. no. #SD5100; mouse/rabbit linker; Celnovte Biotechnology Co., Ltd) was applied for at 37˚C for 30 min. After incubation with the polymer reagent, tissue sections were thoroughly washed with TBS buffer (3x6 min) and incubated with Microstacker™ DAB + Chromogen at 37˚C for 6 min. Slides were buffer washed (2x6 min), counterstained with hematoxylin at 37˚C for 2 min and washed with TBS and dH2O for 6 min respectively. Ultimately, dehydration through graded ethanol solutions as well as 90% xylene was performed and sections were mounted in synthetic resin and were observed under a light microscope.
The IHC results were scored by two independent observers according to the percentage of positively stained cells (0+, 1-25% staining; 1+, 26-50% staining; 2+, 51-75% staining; 3+, 76-100% staining).
The patient cohort included three males and five females with a mean age of 48 years (range, 38-62) at the time of diagnosis (
Grossly, all cases demonstrated a well-demarcated lesion, and lesions were elevated. The average tumor diameter was 21 mm (range, 7-35 mm). The cut surface of the lesions was yellow with parts that were white (
There were solitary nodules in the reticular dermis. The nodules were well circumscribed; however, no fibrous or capsule-like membrane was revealed (
Immunohistochemical staining was positive for CD68 (
Lipidized FH represents a small fraction of dermatofibromas (2%) (
Moreover, Iwata and Fletcher (
Lipidized FH often presents with an increased size compared with common FH (
Histological diagnostic criteria for lipidized FH are as follows: Over 75% of the area is occupied by foamy cells and stromal hyalinization (
However, in patients 5 and 8, the tumors exhibited scant stromal hyalinization and prominent lipid-laden histiocytes. In these cases, lipidized FH should also be differentiated from other benign tumors, such as xanthoma (
In conclusion, lipidized have a wide spectrum. Some cases show the prominent stromal hyalinization, hyalinized vessels and lipid-laden histiocytes, and should be differentiated from the malignant tumors, such as sclerosing epithelioid fibrosarcoma. However, some cases exhibit the prominent lipid-laden histiocytes and scant stromal hyalinization and should be differentiated from the xanthoma. The present study was limited by relative infrequency of lipidized FH and limiting the number of patients in this cohort. Future studies should focus on the microenvironment in different areas of the lipidized FH.
Not applicable.
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
CYL designed the study. FYL and HJW recruited the cases. CYL, FYL, HJW and GYW analyzed the experimental data and composed all figures and tables. CYL wrote the manuscript. FYL and HJW confirm the authenticity of all the raw data. All authors read and approved the final manuscript.
The present study was approved by the 989 Hospital Medical Ethics Committee, Fenlan Lab Medical Ethics Committee and Yexian First People's Hospital Committee. Written informed consent was obtained at the time of the initial data collection for participation.
All patients consented for publication in written form.
The authors declare that they have no competing interests.
Following sectioning, the tumor was yellow in color and mixed with white in patient 2.
Patient 2. (A) A well-circumscribed lesion located at the dermis (magnification, x1). The epidermis exhibited hyperplasia and irregular elongation of the rete ridge (black arrow). (B) Fibroblasts arranged in a storiform pattern (magnification, x7). (C) Fibroblasts arranged in a storiform pattern, and hyalinized collagen fibers transmigrated with normal collagen fibers (magnification, x9). (D) Histiocytes were oval to polygonal in shape with large hypochromatic nuclei, prominent nucleoli and abundantly vacuolated cytoplasm (blue arrow). The fibroblasts exhibited no cytologic atypia, with elongated nuclei, fine chromatin and small basophilic nucleoli (green arrow). (E) Prominent hyalinized vessels were documented (magnification, x40). (F) The histiocytes were strongly positive for CD68 (4+, magnification, x40).
Patient 5. (A) A well-circumscribed lesion located at the dermis (magnification, x0.64). The epidermis exhibited hyperplasia and irregular elongation of the rete ridge (black arrow). (B) Fibroblasts arranged in a storiform pattern (magnification, x4). (C) Prominent hyalinized collagen fibers (magnification, x20). Histiocytes were oval to polygonal in shape with large hypochromatic nuclei, prominent nucleoli and abundantly vacuolated cytoplasm (blue arrow). The fibroblasts exhibited no cytologic atypia, with elongated nuclei, fine chromatin and small basophilic nucleoli (green arrow). (D) Multinucleated Touton-type giant cells (magnification, x20).
Patient 8. (A) A well-circumscribed lesion located at the dermis (magnification, x1). (B) Fibroblasts arranged in a storiform pattern (magnification, x5). (C) Prominent hyalinized collagen fibers (magnification, x18). Histiocytes were oval to polygonal in shape with large hypochromatic nuclei, prominent nucleoli and abundantly vacuolated cytoplasm (blue arrow). The fibroblasts exhibited no cytologic atypia, with elongated nuclei, fine chromatin and small basophilic nucleoli (green arrow). (D) The histiocytes were strongly positive for CD68 (4+, magnification, x40).
Clinical features of patients with lipidized fibrous histiocytoma.
Patient | Age, y | Gender | Location | During | Size, mm | Follow up, mo |
---|---|---|---|---|---|---|
1 | 38 | M | R lower leg | 3 y | 7 | 6 |
2 | 39 | M | L buttock | 5 y | 22 | 8 |
3 | 41 | F | R buttock | 6 y | 35 | 13 |
4 | 56 | F | R buttock | 3 y | 20 | 10 |
5 | 51 | M | R lower leg | 11 mo | 28 | 24 |
6 | 50 | M | R buttock | 1 y | 25 | 22 |
7 | 62 | F | L forearm | 2 y | 20 | 15 |
8 | 49 | M | R shin | 9 mo | 15 | 11 |
F, female; L, left; M, male; mo, months; R, right; y, years.