Fibrous Histiocytoma Research Articles

Desmin and CD34 positivity in cellular fibrous histiocytoma: an immunohistochemical analysis of 100 cases

Cellular benign fibrous histiocytoma (CBFH) represents a morphologic variant of cutaneous fibrous histiocytoma (FH). Because of its relative monomorphism and frequent fascicularity, CBFH can easily be mistaken for a malignancy. In fact, CD34, often used to distinguish CBFH from dermatofibrosarcoma protuberans (DFSP), can also be positive. To add to the confusion, desmin positivity may also be observed in a subset of CBFH. Desmin and CD34 expression often cause interpretative difficulty which may lead to misdiagnosis. Our aim was to examine the incidence of desmin and CD34 expression in CBFH. One hundred consecutive cases of morphologically typical CBFH were retrieved from consultation files. Clinicopathologic and immunohistochemical features were evaluated. SMA positivity was found in tumor cells in 93 of 100 cases (93%). Desmin positivity was found in 32 of 100 cases (32%). CD34 was positive in 6 of 100 cases (6%). There was no evident correlation between immunophenotype and anatomic site or other clinical variables. Frequent desmin (32%) and occasional CD34 (6%) expression are encountered in CBFH. Desmin positivity can be explained on the basis of myofibroblastic differentiation. The occasional CD34 positivity in a subset of CBFH should not be a deterrent from making the correct pathologic diagnosis, based on characteristic morphologic features.

A Case of Pulmonary Sclerosing Hemangioma with an Increased Size and Chest Discomfort on 10 Years’ Follow-up

Pulmonary sclerosing hemangioma is a relatively rare neoplasm of the lung with polymorphic histologic features of 2 unifying cellular components including surface cuboidal cells and interstitial round cells. Pulmonary sclerosing hemangioma typically occurs in middle aged women with asymptomatic, peripheral, solitary, well-circumscribed lesions. Although it is pathologically benign, it reveals size growing and chest symptom. We here report a case of pulmonary sclerosing hemangioma in a 72-year-old woman. She presented chest discomfort. A chest radiography and a chest computed tomography scan showed growing size from 3.2×3.1 cm to 6.0×5.3 cm in left upper lung during 10 years’ follow-up period. Surgical resection of lung revealed a distinct constellation of findings including 2 epithelial cell types, surface cells, and round cells, which form 4 architectural patterns, papillary, sclerotic, solid, and hemorrhagic. She was diagnosed as pulmonary sclerosing hemangioma and chest discomfort disappeared.

Treatment of 28 patients with sclerosing hemangioma (SH) of the lung

BackgroundSclerosing hemangioma (SH) of the lung is a kind of rare pulmonary tumor. Preoperative diagnosis of this tumor is difficult and it is now generally accepted that SH of the lung is benign lesions and surgical excision alone is curative. Herein, we present our experiences of treating 28 patients with SH.MethodsThe medical records of 28 patients with SH from 1994 to 2010 at the Department of Thoracic Surgery in Beijing Chest Hospital were retrospectively reviewed.ResultsThere were 3 male and 25 female patients with sclerosing hemangioma and 50% of the patients were asymptomatic. Preoperatively, all the patients had undergone CT of chest and 5 patients had undergone PET scan but 4 patients were misdiagnosed as malignancy. There was no operative mortality or tumor recurrence despite that three different operative methods were undertaken.ConclusionsSH has a high incidence in middle-aged women. Most of SH is asymptomatic and the symptoms of SH are not related to the tumor size and distribution. The features of chest CT and PET are not specific. Bilateral or multiple lesions should not exclude the possibility of SH. Complete excision of lesion is a curable treatment method and there is no evidence to verify the need of adjuvant therapy.

Expression and significance of stem cell markers in pulmonary sclerosing haemangioma

The two major types of cells of pulmonary sclerosing haemangioma (PSH) with the same origin show significant differences in morphological phenotype. Whether these differences are caused by their different differentiation status is still uncertain. The aim of this study was to analyse their differentiation status by detecting the expression of several stem cell markers in PSH. The expression of stem cell markers was examined by using streptavidin peroxidase (SP) immunohistochemisty in 45 PSH specimens. Also, the two types of cells were, respectively, captured by laser capture microdissection (LCM) from 28 PSH specimens, and total RNA was then extracted followed by reverse transcription-polymerase chain reaction (RT-PCR). The results demonstrated that the expression rates of ABCG2, Notch1 and Notch3 in polygonal cells were significantly higher than those in cuboidal cells (P < 0.05), and the expression levels of ABCG2, Notch3 and Jagged1 in polygonal cells were clearly higher than those in cuboidal cells (P < 0.05). The data obtained provided evidence that the two types of cells in PSH may be different in differentiation status. The differentiation difference between the two types of cells might lead to variation in their morphological phenotype.

Fine‐needle aspiration diagnosis of sclerosing hemangioma (pneumocytoma): Report of a case and review of the literature

Sclerosing hemangioma (pneumocytoma) is a rare benign lung tumor with uncertain histogenesis but characteristic histology. Reports of the cytopathology of this tumor are even rarer with only a handful of cases in the literature--many of these incorrectly diagnosed by cytology initially. Herein, we describe a case of sclerosing hemangioma diagnosed prima facie by fine-needle aspiration cytology. A cell block preparation with accompanying immunohistochemistry was instrumental in making the diagnosis. A review of the literature is also presented.

Clinicopathological Analysis in 20 Patients with Pulmonary Sclerosing Hemangioma

Clinicopathological Analysis in 20 Patients with Pulmonary Sclerosing Hemangioma

In pulmonary sclerosing hemangioma expression of β-catenin, Axin, and C-myc differs between the two cell types

Previous studies have shown that pulmonary sclerosing hemangioma is a tumor derived from primitive respiratory epithelium, but its character and the differentiation status of the two cell types (polygonal and cuboidal) composing the lesion are still controversial. We hypothesize that the polygonal cells are immature compared with cuboidal cells and have higher proliferative activity. To further study this question, we examined the expression of β-catenin, Axin, and C-myc by immunostaining in 45 primary sclerosing hemangioma (PSH) specimens. The two cell types were captured by laser capture microdissection from 28 PSH specimens, and total RNA was extracted. Messenger RNA (mRNA) expression of Axin and C-myc was examined by reverse transcription polymerase chain reaction (RT-PCR). By immunostaining, β-catenin was predominantly strongly expressed on the cell membrane of cuboidal cells, while in polygonal cells, β-catenin was predominantly expressed in the cytoplasm and significantly decreased on cell membranes. Axin was expressed in cuboidal cells in 93 % of our 45 cases, but only expressed in 18 % of these in polygonal cells. C-myc expression in polygonal cells was significantly stronger than in cuboidal cells (P < 0.05). RT-PCR showed that the expression level of Axin mRNA in cuboidal cells was significantly higher than in polygonal cells (P < 0.05), and expression level of C-myc mRNA in polygonal cells was significantly higher than in cuboidal cells (P < 0.05).The two PHS cell types have distinct expression of β-catenin, Axin, and C-myc, suggesting that their differentiation status may be different. The higher expression of C-myc in polygonal cells suggests that these cells might have higher proliferative activity.

Clinical and Pathologic Characteristics and Surgical Management of Benign Fibrous Histiocytoma of the Mandible: A Case Report

Benign fibrous histiocytomas (BFHs) of the bone are unusual mesenchymal neoplasms arising from fibroblasts and histocytes. These fibroblasts and histocytes are arranged in a storiform pattern; thus, BFHs are often confused with histologically similarly fibrohistiocytic lesions such as nonossifying fibromas (NOFs), fibrous cortical defects, and metaphyseal fibrous defects. BFHs of the soft tissues are well-recognized entities; however, BFHs occurring in the bone are rare. Thus, few unique pathologic features that might aid in the diagnosis and treatment have been described. BFHs of bone appear most often in the long bones, with histologic characteristics identical to BFHs in the soft tissue. However, lesions arising in the jaws are so rare only a few cases have been reported. Our case report describes the clinicopathologic characteristics and surgical management of a BFH in the mandible. BFH of the flat bones have distinct clinical, radiologic, and pathologic characteristics and require unique surgical management.

Benign fibrous histiocytoma of the external auditory canal: Case report and literature review

Background: The benign fibrous histiocytoma (BFH) is a mainly dermal neoplasm composed of a mixture of fibroblastic and histiocytic cells. It is usually reported as occurring on the extremity, retroperitoneum or orbit but not commonly in the other head and neck regions.Methods: A ten-year old girl presented with a right external auditory meatal mass for 6 months. Clinical examination showed a small, firm non-tender swelling on the antero-inferior part of the cartilagenous external auditory canal. An excisional biopsy was performed without complication.Results: Clinical and histopathological examinations with immunohistochemical studies were consistent with the diagnosis of BFH of the external auditory canal. There was no local recurrence to date.Conclusions: BFH is an uncommon benign neoplasm of the head and neck and none has been previously described occurring in the external auditory canal. Complete local excision is the mainstay of treatment with excellent prognosis. DOI: http://dx.doi.org/10.3329/bjo.v18i1.10424 Bangladesh J Otorhinolaryngol 2012; 18(1): 77-80

Histogenesis of pulmonary sclerosing hemangioma

To investigate the histogenesis of pulmonary sclerosing hemangioma (PSH). Tissue microarray and immunohistochemical technique were used to detect the expression of pan-cytokeratin, epithelial membrane antigen(EMA), vimentin, thyroid transcription factor (TTF)-1, napsin A, synaptophysin, chromogranin A, CD56, E-cadherin, β-catenin, CD117, CD68 and transforming growth factor(TGF)-β1 in 49 cases of PSH. Immunohistochemistry revealed that all cuboidal surface cells expressed pan-cytokeratin, EMA, TTF-1 and napsin A. The polygonal cells expressed EMA, TTF-1, napsin A (positive rate 16.3%, 8/49), but not pan-cytokeratin. Both types of cells were negative for synaptophysin, chromogranin A and CD56. Strong positive staining for E-cadherin and β-catenin appeared on the membrane of cuboidal cells in all PSH, with cytoplasm staining for β-catenin as well. The expression levels of these adhesion molecules decreased in the polygonal cells, with the staining localized to the cytoplasm. E-cadherin staining was not detected or was weak. β-catenin staining was not detected on the cell membrane but partially in the cytoplasm. The polygonal cells stained strongly for vimentin, while only a few cuboidal cells were positive. CD117 and CD68 positive inflammatory cells were scattered between the polygonal cells, which was consistent with the distribution of TGF-β1 positive cells. PSH originates from the primitive respiratory epithelium, and polygonal stromal cells may be derived from epithelial-mesenchymal transformation of the cuboidal cells. TGF-β1 may play an important role in the formation of sclerosing hemangioma.

High level of Ets‐related gene expression has high specificity for prostate cancer: a tissue microarray study of 11 483 cancers

TMPRSS2-ERG fusion resulting in strong Ets-related gene (ERG) overexpression occurs in about 50% of prostate cancers. This study was undertaken to determine the prevalence of ERG overexpression in other tumour types as well as in normal tissues. A total of 11 483 tumours and 72 different normal tissue types were analysed in a tissue microarray format. Strong nuclear ERG overexpression was found in 36.7% of prostate carcinomas as well as in various vascular tumours, including Kaposi sarcomas (91.7%), angiosarcomas (100%) and haemangiomas (90.9%). Moderate to strong nuclear ERG immunostaining was also observed in thymoma (6.1%). Weak to moderate ERG staining was found in a small number of squamous cell carcinomas of the skin, squamous carcinomas of the lung, malignant mesotheliomas, carcinosarcomas of the uterus, gastrointestinal stromal tumours, hepatocellular carcinomas, teratomas of the testis, anaplastic carcinomas of the thyroid, giant cell tumours of the tendon sheath and benign fibrous histiocytomas of the skin. ERG overexpression was not seen in 8886 samples from 132 other tumour types and subtypes. Within normal tissues, immunohistochemically detectable ERG overexpression was restricted to endothelial cells and subsets of lymphocytes. The high specificity of ERG expression in both normal and neoplastic tissues suggests a very narrow biological role for ERG in highly selected tissues.

Segmentectomy for giant pulmonary sclerosing haemangiomas with high serum KL-6 levels

We describe a 61-year old female patient with a giant pulmonary sclerosing haemangioma (PSH) and an extremely high preoperative serum KL-6 level. During an annual health screening, the patient showed a posterior mediastinal mass on chest radiography. Chest computed tomography and magnetic resonance imaging revealed a well-circumscribed 60 mm diameter nodule with a marked contrast enhancement in the left lower lobe. The preoperative serum KL-6 level was elevated to 8204 U/ml. We performed a four-port thoracoscopic basal segmentectomy and lymph node sampling for diagnosis and therapy. The postoperative diagnosis showed PSH. The serum KL-6 level decreased dramatically with tumour resection. To the best of our knowledge, this is the first report of a patient with PSH showing a high serum KL-6 level.

Unusual spindle cell tumours at the base of tongue (solitary fibrous tumour and malignant fibrous histiocytoma): report of two cases and review of literature

AbstractObjective: Two cases of rare spindle cell tumours of the tongue are described. Solitary fibrous tumour is a mesenchymal neoplasm which is usually benign and malignant fibrous histiocytoma is a high grade aggressive sarcoma.Materials and methods: Two patients presented to us with a mass at the base of the tongue. It is essential to keep tumours such as SFT and MFH in the differential diagnosis of lesions at the tongue base.Results: Histological similarities with other soft tissue tumours may present as a diagnostic challenge and immunohistochemistry plays a pivotal role to clinch the diagnosis.Conclusion: Surgical excision is the treatment of choice as they respond poorly to radiotherapy.

Pulmonary sclerosing haemangioma with metastatic spread to stomach

Pulmonary sclerosing haemangioma with metastatic spread to stomach

Aneurysmal fibrous histiocy toma: a clinical and histopathologic review of five cases

Objective To understand the clinical and histopathologic diagnostic criteria for aneurysmal fibrous histiocytoma (AFH).Methods The clinical and histopathological features of 5 patients with AFH were retrospectively reviewed.Results There were 3 males and 2 females in these patients.All the tumors clinically manifested as dark erythematous or brown nodules.Three cases had a recent history of rapid growth.The lesions were located on the limbs (n =3),or chest and lower mandible (n =2).Histopathological examination of skin biopsies showed typical features of dermatofibroma,accompanied by many irregular cleftlike or cavernous blood-filled spaces with numerous hemosiderin pigments in all of these cases.Immunohistochemically,the tumor cells were immunoreactive to vimentin and CD68 but negative for CD34 or CD31.Conclusions In view of a history of recent rapid growth,the presence of hemorrhagic pseudocysts and high vascularity,AFH should be differentiated from angiosarcoma and angiomatoid fibrous histiocytoma. Key words: Histiocytoma, benign fibrous; Clinical and histological features

Hyalin Perivascular Arcs and Rings in Sclerosing Atypical Fibroxanthomas

To the Editors: Several variants of atypical fibroxanthoma (AFX) are split based on cytomorphology, for example, clear cell, granular cell, and spindle cell nonpleomorphic types.1 Nine cases of an unusual variant of AFX with keloidal tumoral sclerosis were presented by Kim and McNiff,2 following in from an anecdotal report3 and series of “keloidal” AFX. In several cases, “the keloidal collagen also formed ring-shaped structures surrounding CD31-positive vascular structures.” This report conveys our research on the perivascular sclerosis in a subset of 10 AFX examples with collagenous arcs and rings (Table 1).TABLE 1: 10 Prospectively Selected Cases of Sclerosing AFXThis curious arc and ring pattern of hyalinized collagen in some AFXs is morphologically similar to the always superficially located perivascular linear and tubular sclerosis in a minority of dermatofibromas. It is cautioned that the keloidal collagen associated with atypical fibrohistiocytic cells in AFX may erroneously lead to the diagnosis of “keloidal dermatofibroma.4” Interesting in this regard, it has been said that the spectrum of fibrous histiocytoma (a diagnostic term utilized as a synonym for dermatofibroma) can be viewed somewhat more broadly, with dermatofibroma (DF) at one pole and with its “malignant analogue” AFX at the other.5 In both entities, AFX and DF, a sparse central component of CD31-positive cells in the sclerotic arcs and rings deemed endothelial cells led to our initial hypothesis that the “keloidal collagen” is actually vascular basement membrane material of effete capillaries. Laminins, nidogens, and perlecans are arranged into highly organized supramolecular architectures by vascular basement membranes.6 We proposed the adherence of these elements likely explained the homogeneous (hyalinized) appearance of this material by obscuring its fibrillar texture (Figs. 1, 2). However, reactions for collagen type IV (specific for vascular basement membrane material)7 were negative for the morphologically similar curvilinear and circular material in both our AFX and DF examples. Also unreactive were the coarse hyalinized collagen bands of a common keloid, which like dermal collagen, are predominantly collagen type I.8FIGURE 1: Atypical fibroxanthoma. A, Hyalin rings surround small vessels in lower right of this AFX overlain by impetiginized parakeratosis (×400). B, Pleomorphic histology includes the usual tumor giant cells (×200). C, Dual immunohistochemical reaction: central endothelial cells label red for CD31 and rest upon an actin-positive (brown) pericyte layer (×700).FIGURE 2: Dermatofibroma. A, Sclerotic arcs and rings surround central cells in effete vessels; hemosiderin is the brown pigment (×700). B, A dual immunohistochemical reaction labels central endothelial cells red for CD31 although actin-positive pericytes are decorated brown as they layer against the external sclerotic ring (×700). C, A collagen IV reaction labels a thin endothelial basement membrane brown that lies between the endothelial cells and pericytes; the thick sclerotic collagenous rind around the vessel is nonreactive, that is, not thickened endothelial basement membrane (×1000).Pericytes are actin-positive cells situated in the basement membranes outside the endothelium of capillaries and venules. During the onset of angiogenesis the intramural pericytes leave the microvascular wall and enter the perivascular space, where they become collagen producing stromal cells. Sundberg et al9 identified 4 stages of pericyte migration/progression from the endothelium to a collagen-synthesizing fibroblast in the interstitium. Pericytes have been identified in the wound-healing process via their expression of platelet-derived growth factor, a moiety which enhances neoformation of collagen and is associated with a collagen-rich dense tumor stroma, and have been shown to differentiate into collagen-producing cells during liver fibrosis.10 Double immunohistochemical reactions in our AFXs and DFs alike display concentric pattern: luminal CD31-positive endothelial cells within a ring of actin-positive pericytes that face the external rim of sclerotic material (Figs. 1C, 2B). Lesional cells of both DF and AFX show no consistent propensity to border the sclerotic material, discounting any role they might have in producing it. This leaves the pericyte stimulated to differentiate into fibroblasts when in a proliferative “fibrohistiocytic” environment, as the sole architect because it is consistently found within the rings as expected. Sclerotic hyalin rings similar to the material under discussion have been illustrated in hemangiopericytomas.10 The consistent localization of the pericyte to within the hyalin rings of the 10 sclerosing AFXs in this series supports the hypothesis that this material is synthesized by pericytes, a proposition that should be tested by more sophisticated studies. Larisa M. Lehmer, MA Bruce D. Ragsdale, MD Western Dermatopathology with Central Coast Pathology and Santa Barbara Pathology Laboratory, San Luis Obispo, CA 93401

Surgery treatment for pulmonary sclerosing hemangioma

To investigate the clinicopathological features and surgical treatment of pulmonary sclerosing hemangioma (PSH). Clinic data of PSH patients admitted by surgical resection from January 1985 to December 2010 was analyzed retrospectively. One hundred and sixty-five patients were enrolled in the study. There were 27 male and 138 female patients with a mean age of (48 ± 13) years. Seventy-nine patients were asymptomatic at the time of diagnosis. Eighty-nine tumors arose in the right lung (27 in right upper lobe, 24 in right middle lobe, 34 in right lower lobe, 2 in right upper lobe with invasion of right middle lobe, 1 in right middle lobe with invasion of right lower lobe, and 1 case with multiple lobe lesions), 75 in the left (33 in left upper lobe, 42 in left lower lobe), and 1 in the bilateral. There were huge mass lesions in 2 cases, endobronchial lesions in 2 cases, and multiple lesions in 6 cases. The mean size of the lesion was (2.6 ± 0.9) cm (ranging from 0.9 to 10.0 cm). Forty-eight cases (29.1%) were misdiagnosed as malignancies preoperatively, and 41 cases (24.8%) were misdiagnosed intraoperatively. Resections were performed by means of video-assisted thoracoscopy (n = 53) and thoracotomy (n = 112). Surgical resection included pulmonary wedge excision in 61 patients, lobectomy in 89 patients, right bilobectomy in 5 patients, anatomic segmentectomy in 2 patient, enucleation in 6 patients, and synchronous bilateral pulmonary wedge resection in 1 patient. Operative mortality and morbidity occurred in 0 and 2 (4.3%) patients, respectively. Mean follow-up was 34.7 months (ranging from 6 to 62 months). There was no local recurrence or death from PSH. PSH is a rare benign lung tumor. It is difficult to make accurate diagnosis preoperatively, and sometimes even intraoperative frozen sections can't differentiate it from malignant tumors. Surgical resection is usually indicated for definite diagnosis and treatment. Partial resection is a sufficient treatment in view of uncommon tumor recurrence. Thoracoscopic surgery is recommended for PSH.

Experiences with total femur replacement for malignant bone and soft tissue tumors

Background: Reasonable function can be restored after total femur replacement after massive resection of bone and soft tissue sarcomas of the thigh. The type of femoral prosthesis and surgical approach are tailored to the clinical characteristics of individual patients and to tumor anatomy. Though the complication rate is high, total femur replacement offers the patient limb salvage and a chance at functional ambulation. Objective: We described the function and complications of total femur replacement performed at the institution as well as relevant literature reviews. Methods: Seven patients underwent total femur replacement for the treatment of malignant bone and soft tissue tumors of the lower extremities between 1992 and 2010 at our institute. Ages ranged from 12 to 68 (mean=34) years. The tumor was pathologically diagnosed as osteosarcoma in two patients, Ewing’s sarcoma in two, chondrosarcoma (grade 3) in one, soft tissue malignant fibrous histiocytoma in one, and bone metastasis from renal cancer in one. Follow-up periods ranged from 1 to 17 years (mean = six years three months). All patients underwent wide resection, using the Howmedica Modular and Reconstruction System in five cases and the Kyocera Limb Salvage System in two cases. Function, complications and outcomes were evaluated in these patients, and the usefulness of the operative procedures is discussed herein. Results: The mean functional score was 60%. X-ray examination revealed migration in only one case. Complications were infection (n=2), bipolar head dislocation (n=1) and patellar fracture (n=2). The outcomes were DOD (died of disease) in three cases, NED (no evidence of disease) in two, AWD (alive with disease) in one, and CDF (continuous disease free) in one. Conclusion: The results suggest that total femur replacement is useful as a means of reconstructing affected limbs in patients with malignant bone and soft tissue tumors, but that latissimus dorsi muscle transplantation, as well as other procedures, must also be considered in cases requiring extensive soft tissue resection to prevent infection. Furthermore, early one-stage revision is advisable in cases showing signs of infection. Keywords: Femoral prosthesis, functional outcomes, malignant tumors, total femur replacement

Benign fibrous histiocytoma arising from the right shoulder: Is immunohistochemical staining always required for a definitive diagnosis?

INTRODUCTIONFibrous histiocytomas are divided into two subgroups: malignant and benign fibrous histiocytomas (BFHs). BFH is one of the most common tumors of the superficial and deep soft tissues; it is commonly found on the skin and presents as a slow-growing solitary nodule made up of a mixture of fibroblastic and histiocytic cells. PRESENTATION OF CASEIn this study, we present the case of a 45-year-old female who was histopathologically diagnosed with dermatofibrosarcoma protuberans (DFSP) and received radiotherapy, but whose diagnosis was changed to BFH based on subsequent immunohistochemical analyses. DISCUSSIONBFH is a mesenchymal soft-tissue tumor with fibroblastic and histiocytic differentiation. Differential diagnosis for BFH found in deeper tissues includes other aggressive fibrohistiocytic lesions, such as DFSP and malignant fibrous histiocytoma. Differentiating among these tumors is crucial in selecting the correct surgical strategy and patient management in the postoperative period. In most cases, the pleomorphism and atypical mitotic activity seen histopathologically are sufficient for the differentiation between benign and malignant tumors. Immunohistochemical staining methods should be used in cases that are difficult to diagnose. The treatment of choice for BFH is wide resection of the tumor, which results in an excellent prognosis and low recurrence rate. In agreement with cases reported in the literature, our case confirms that wide excision is adequate to prevent the recurrence of the tumor. CONCLUSIONAlthough benign fibrous histiocytomas is rare, it must be considered in the differential diagnosis of tumors arising from the soft-tissue.

The Diagnostic Significance of Infiltration Pattern and Perilesional Lymphoid Cell Infiltrate in Dermatofibroma

Dear Editor: We read, with great interest, the manuscript by Han et al.1, entitled clinical and histopathological study of 122 cases of dermatofibroma (benign fibrous histiocytoma). We completely agree with the histopathological classification of dermatofibroma (DF) and are grateful for the educational figures. In their study, the authors describe the presence of lymphoid follicles, according to the classification of DF. Furthermore, we would like to suggest different histopathologic findings important to the diagnosis of DF. Here, we refer specifically to subcutaneous DF, and we believe it should be clearly differentiated from other diseases. Subcutaneous DF is a rare variant of DF and may be difficult to diagnose due to its histopathological similarities with dermatofibrosarcoma protuberans (DFSP) and atypical fibroxanthoma. The most useful histopathologic feature in this differential is a pattern of extension into the subcutaneous tissue. In addition to smooth, well defined patterns, radial or vertical-with-wedge-shaped patterns have been observed as common patterns of infiltration in subcutaneous DF2. In a study by Gleason and Fletcher3, on clinicopathological assessment of deep benign fibrous histiocytoma, the focal perilesional lymphoid infiltrate, often with follicle formation, and peripheral hyalized collagen were observed as relatively common histopathological findings in subcutaneous DF, in contrast with those of DFSP. These results are in accordance with criteria published in 1994 by Zelger et al.4 to discriminate subcutaneous DF from DFSP. Lymphoid follicles in particular have been reported in a variety of subcutaneous inflammatory diseases, including lupus panniculitis, morphea, erythema induratum, and necrobiosis lipoidica5. They are also observed in malignant tumors such as desmoplastic melanoma and leiomyoma6. We also observed a case of deep penetrating DF showing perilesional lymphoid follicles (Fig. 1). In conclusion, histopathologic findings, such as perilesional lymphoid follicle and hyalized collagen, were not specific to the recognition of subcutaneous DF, yet we believe they have diagnostic significance in the differential diagnosis between DF and DFSP. Fig. 1 (A) A well-circumscribed nodule deeply localized into the subcutaneous tissue (H&E, ×40). (B, C) Scattered collections of lymphocytes and sclerotic collagen (arrows) at the periphery of the tumor (H&E, B: ×100, C: ×400). ...